/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.dbcp.dbcp2;

import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.lang.management.ManagementFactory;
import java.nio.charset.StandardCharsets;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Properties;
import java.util.logging.Logger;

import javax.management.InstanceAlreadyExistsException;
import javax.management.JMException;
import javax.management.MBeanRegistration;
import javax.management.MBeanRegistrationException;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.NotCompliantMBeanException;
import javax.management.ObjectName;
import javax.sql.DataSource;

import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.dbcp.pool2.PooledObject;
import org.apache.tomcat.dbcp.pool2.impl.AbandonedConfig;
import org.apache.tomcat.dbcp.pool2.impl.BaseObjectPoolConfig;
import org.apache.tomcat.dbcp.pool2.impl.GenericKeyedObjectPoolConfig;
import org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool;
import org.apache.tomcat.dbcp.pool2.impl.GenericObjectPoolConfig;

/**
 * <p>Basic implementation of <code>javax.sql.DataSource</code> that is
 * configured via JavaBeans properties.  This is not the only way to
 * combine the <em>commons-dbcp</em> and <em>commons-pool</em> packages,
 * but provides a "one stop shopping" solution for basic requirements.</p>
 *
 * @author Glenn L. Nielsen
 * @author Craig R. McClanahan
 * @author Dirk Verbeeck
 * @since 2.0
 */
public class BasicDataSource implements DataSource, BasicDataSourceMXBean, MBeanRegistration {

    private static final Log log = LogFactory.getLog(BasicDataSource.class);

    static {
        // Attempt to prevent deadlocks - see DBCP - 272
        DriverManager.getDrivers();
        try {
            // Load classes now to prevent AccessControlExceptions later
            // A number of classes are loaded when getConnection() is called
            // but the following classes are not loaded and therefore require
            // explicit loading.
            if (Utils.IS_SECURITY_ENABLED) {
                ClassLoader loader = BasicDataSource.class.getClassLoader();
                String dbcpPackageName = BasicDataSource.class.getPackage().getName();
                loader.loadClass(dbcpPackageName + ".BasicDataSource$PaGetConnection");
                loader.loadClass(dbcpPackageName + ".DelegatingCallableStatement");
                loader.loadClass(dbcpPackageName + ".DelegatingDatabaseMetaData");
                loader.loadClass(dbcpPackageName + ".DelegatingPreparedStatement");
                loader.loadClass(dbcpPackageName + ".DelegatingResultSet");
                loader.loadClass(dbcpPackageName + ".PoolableCallableStatement");
                loader.loadClass(dbcpPackageName + ".PoolablePreparedStatement");
                loader.loadClass(dbcpPackageName + ".PoolingConnection$StatementType");
                loader.loadClass(dbcpPackageName + ".PStmtKey");

                String poolPackageName = PooledObject.class.getPackage().getName();
                loader.loadClass(poolPackageName + ".impl.LinkedBlockingDeque$Node");
                loader.loadClass(poolPackageName + ".impl.GenericKeyedObjectPool$ObjectDeque");
            }
        } catch (ClassNotFoundException cnfe) {
            throw new IllegalStateException("Unable to pre-load classes", cnfe);
        }
    }

    // ------------------------------------------------------------- Properties

    /**
     * The default auto-commit state of connections created by this pool.
     */
    private volatile Boolean defaultAutoCommit = null;

    /**
     * Returns the default auto-commit property.
     *
     * @return true if default auto-commit is enabled
     */
    @Override
    public Boolean getDefaultAutoCommit() {
        return defaultAutoCommit;
    }

    /**
     * <p>Sets default auto-commit state of connections returned by this
     * datasource.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param defaultAutoCommit default auto-commit value
     */
    public void setDefaultAutoCommit(Boolean defaultAutoCommit) {
        this.defaultAutoCommit = defaultAutoCommit;
    }


    /**
     * The default read-only state of connections created by this pool.
     */
    private transient Boolean defaultReadOnly = null;

    /**
     * Returns the default readOnly property.
     *
     * @return true if connections are readOnly by default
     */
    @Override
    public Boolean getDefaultReadOnly() {
        return defaultReadOnly;
    }

    /**
     * <p>Sets defaultReadonly property.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param defaultReadOnly default read-only value
     */
    public void setDefaultReadOnly(Boolean defaultReadOnly) {
        this.defaultReadOnly = defaultReadOnly;
    }

    /**
     * The default TransactionIsolation state of connections created by this pool.
     */
    private volatile int defaultTransactionIsolation =
        PoolableConnectionFactory.UNKNOWN_TRANSACTIONISOLATION;

    /**
     * Returns the default transaction isolation state of returned connections.
     *
     * @return the default value for transaction isolation state
     * @see Connection#getTransactionIsolation
     */
    @Override
    public int getDefaultTransactionIsolation() {
        return this.defaultTransactionIsolation;
    }

    /**
     * <p>Sets the default transaction isolation state for returned
     * connections.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param defaultTransactionIsolation the default transaction isolation
     * state
     * @see Connection#getTransactionIsolation
     */
    public void setDefaultTransactionIsolation(int defaultTransactionIsolation) {
        this.defaultTransactionIsolation = defaultTransactionIsolation;
    }


    private Integer defaultQueryTimeout = null;

    /**
     * Obtain the default query timeout that will be used for {@link java.sql.Statement Statement}s
     * created from this connection. <code>null</code> means that the driver
     * default will be used.
     */
    public Integer getDefaultQueryTimeout() {
        return defaultQueryTimeout;
    }


    /**
     * Set the default query timeout that will be used for {@link java.sql.Statement Statement}s
     * created from this connection. <code>null</code> means that the driver
     * default will be used.
     */
    public void setDefaultQueryTimeout(Integer defaultQueryTimeout) {
        this.defaultQueryTimeout = defaultQueryTimeout;
    }


    /**
     * The default "catalog" of connections created by this pool.
     */
    private volatile String defaultCatalog = null;

    /**
     * Returns the default catalog.
     *
     * @return the default catalog
     */
    @Override
    public String getDefaultCatalog() {
        return this.defaultCatalog;
    }

    /**
     * <p>Sets the default catalog.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param defaultCatalog the default catalog
     */
    public void setDefaultCatalog(String defaultCatalog) {
        if (defaultCatalog != null && defaultCatalog.trim().length() > 0) {
            this.defaultCatalog = defaultCatalog;
        }
        else {
            this.defaultCatalog = null;
        }
    }

    /**
     * The property that controls if the pooled connections cache some state
     * rather than query the database for current state to improve performance.
     */
    private boolean cacheState = true;

    /**
     * Returns the state caching flag.
     *
     * @return  the state caching flag
     */
    @Override
    public boolean getCacheState() {
        return cacheState;
    }

    /**
     * Sets the state caching flag.
     *
     * @param cacheState    The new value for the state caching flag
     */
    public void setCacheState(boolean cacheState) {
        this.cacheState = cacheState;
    }

    /**
     * The instance of the JDBC Driver to use.
     */
    private Driver driver = null;

    /**
     * Returns the JDBC Driver that has been configured for use by this pool.
     * <p>
     * Note: This getter only returns the last value set by a call to
     * {@link #setDriver(Driver)}. It does not return any driver instance that
     * may have been created from the value set via
     * {@link #setDriverClassName(String)}.
     *
     * @return the JDBC Driver that has been configured for use by this pool
     */
    public synchronized Driver getDriver() {
        return driver;
    }

    /**
     * Sets the JDBC Driver instance to use for this pool.
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param driver
     */
    public synchronized void setDriver(Driver driver) {
        this.driver = driver;
    }

    /**
     * The fully qualified Java class name of the JDBC driver to be used.
     */
    private String driverClassName = null;

    /**
     * Returns the jdbc driver class name.
     * <p>
     * Note: This getter only returns the last value set by a call to
     * {@link #setDriverClassName(String)}. It does not return the class name of
     * any driver that may have been set via {@link #setDriver(Driver)}.
     *
     * @return the jdbc driver class name
     */
    @Override
    public synchronized String getDriverClassName() {
        return this.driverClassName;
    }

    /**
     * <p>Sets the jdbc driver class name.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param driverClassName the class name of the jdbc driver
     */
    public synchronized void setDriverClassName(String driverClassName) {
        if (driverClassName != null && driverClassName.trim().length() > 0) {
            this.driverClassName = driverClassName;
        }
        else {
            this.driverClassName = null;
        }
    }

    /**
     * The class loader instance to use to load the JDBC driver. If not
     * specified, {@link Class#forName(String)} is used to load the JDBC driver.
     * If specified, {@link Class#forName(String, boolean, ClassLoader)} is
     * used.
     */
    private ClassLoader driverClassLoader = null;

    /**
     * Returns the class loader specified for loading the JDBC driver. Returns
     * <code>null</code> if no class loader has been explicitly specified.
     * <p>
     * Note: This getter only returns the last value set by a call to
     * {@link #setDriverClassLoader(ClassLoader)}. It does not return the class
     * loader of any driver that may have been set via
     * {@link #setDriver(Driver)}.
     */
    public synchronized ClassLoader getDriverClassLoader() {
        return this.driverClassLoader;
    }

    /**
     * <p>Sets the class loader to be used to load the JDBC driver.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param driverClassLoader the class loader with which to load the JDBC
     *                          driver
     */
    public synchronized void setDriverClassLoader(
            ClassLoader driverClassLoader) {
        this.driverClassLoader = driverClassLoader;
    }

    /**
     * True means that borrowObject returns the most recently used ("last in")
     * connection in the pool (if there are idle connections available).  False
     * means that the pool behaves as a FIFO queue - connections are taken from
     * the idle instance pool in the order that they are returned to the pool.
     */
    private boolean lifo = BaseObjectPoolConfig.DEFAULT_LIFO;

    /**
     * Returns the LIFO property.
     *
     * @return true if connection pool behaves as a LIFO queue.
     */
    @Override
    public synchronized boolean getLifo() {
        return this.lifo;
    }

    /**
     * Sets the LIFO property. True means the pool behaves as a LIFO queue;
     * false means FIFO.
     *
     * @param lifo the new value for the LIFO property
     *
     */
    public synchronized void setLifo(boolean lifo) {
        this.lifo = lifo;
        if (connectionPool != null) {
            connectionPool.setLifo(lifo);
        }
    }

    /**
     * The maximum number of active connections that can be allocated from
     * this pool at the same time, or negative for no limit.
     */
    private int maxTotal = GenericObjectPoolConfig.DEFAULT_MAX_TOTAL;

    /**
     * <p>Returns the maximum number of active connections that can be
     * allocated at the same time.
     * </p>
     * <p>A negative number means that there is no limit.</p>
     *
     * @return the maximum number of active connections
     */
    @Override
    public synchronized int getMaxTotal() {
        return this.maxTotal;
    }

    /**
     * Sets the maximum total number of idle and borrows connections that can be
     * active at the same time. Use a negative value for no limit.
     *
     * @param maxTotal the new value for maxTotal
     * @see #getMaxTotal()
     */
    public synchronized void setMaxTotal(int maxTotal) {
        this.maxTotal = maxTotal;
        if (connectionPool != null) {
            connectionPool.setMaxTotal(maxTotal);
        }
    }

    /**
     * The maximum number of connections that can remain idle in the
     * pool, without extra ones being destroyed, or negative for no limit.
     * If maxIdle is set too low on heavily loaded systems it is possible you
     * will see connections being closed and almost immediately new connections
     * being opened. This is a result of the active threads momentarily closing
     * connections faster than they are opening them, causing the number of idle
     * connections to rise above maxIdle. The best value for maxIdle for heavily
     * loaded system will vary but the default is a good starting point.
     */
    private int maxIdle = GenericObjectPoolConfig.DEFAULT_MAX_IDLE;

    /**
     * <p>Returns the maximum number of connections that can remain idle in the
     * pool. Excess idle connections are destroyed on return to the pool.
     * </p>
     * <p>A negative value indicates that there is no limit</p>
     *
     * @return the maximum number of idle connections
     */
    @Override
    public synchronized int getMaxIdle() {
        return this.maxIdle;
    }

    /**
     * Sets the maximum number of connections that can remain idle in the
     * pool. Excess idle connections are destroyed on return to the pool.
     *
     * @see #getMaxIdle()
     * @param maxIdle the new value for maxIdle
     */
    public synchronized void setMaxIdle(int maxIdle) {
        this.maxIdle = maxIdle;
        if (connectionPool != null) {
            connectionPool.setMaxIdle(maxIdle);
        }
    }

    /**
     * The minimum number of active connections that can remain idle in the
     * pool, without extra ones being created when the evictor runs, or 0 to create none.
     * The pool attempts to ensure that minIdle connections are available when the idle object evictor
     * runs. The value of this property has no effect unless {@link #timeBetweenEvictionRunsMillis}
     * has a positive value.
     */
    private int minIdle = GenericObjectPoolConfig.DEFAULT_MIN_IDLE;

    /**
     * Returns the minimum number of idle connections in the pool. The pool attempts
     * to ensure that minIdle connections are available when the idle object evictor
     * runs. The value of this property has no effect unless {@link #timeBetweenEvictionRunsMillis}
     * has a positive value.
     *
     * @return the minimum number of idle connections
     * @see GenericObjectPool#getMinIdle()
     */
    @Override
    public synchronized int getMinIdle() {
        return this.minIdle;
    }

    /**
     * Sets the minimum number of idle connections in the pool. The pool attempts
     * to ensure that minIdle connections are available when the idle object evictor
     * runs. The value of this property has no effect unless {@link #timeBetweenEvictionRunsMillis}
     * has a positive value.
     *
     * @param minIdle the new value for minIdle
     * @see GenericObjectPool#setMinIdle(int)
     */
    public synchronized void setMinIdle(int minIdle) {
       this.minIdle = minIdle;
       if (connectionPool != null) {
           connectionPool.setMinIdle(minIdle);
       }
    }

    /**
     * The initial number of connections that are created when the pool
     * is started.
     */
    private int initialSize = 0;

    /**
     * Returns the initial size of the connection pool.
     *
     * @return the number of connections created when the pool is initialized
     */
    @Override
    public synchronized int getInitialSize() {
        return this.initialSize;
    }

    /**
     * <p>Sets the initial size of the connection pool.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param initialSize the number of connections created when the pool
     * is initialized
     */
    public synchronized void setInitialSize(int initialSize) {
        this.initialSize = initialSize;
    }

    /**
     * The maximum number of milliseconds that the pool will wait (when there
     * are no available connections) for a connection to be returned before
     * throwing an exception, or <= 0 to wait indefinitely.
     */
    private long maxWaitMillis =
            BaseObjectPoolConfig.DEFAULT_MAX_WAIT_MILLIS;

    /**
     * Returns the maximum number of milliseconds that the pool will wait
     * for a connection to be returned before throwing an exception. A value
     * less than or equal to zero means the pool is set to wait indefinitely.
     *
     * @return the maxWaitMillis property value
     */
    @Override
    public synchronized long getMaxWaitMillis() {
        return this.maxWaitMillis;
    }

    /**
     * Sets the MaxWaitMillis property. Use -1 to make the pool wait
     * indefinitely.
     *
     * @param maxWaitMillis the new value for MaxWaitMillis
     * @see #getMaxWaitMillis()
     */
    public synchronized void setMaxWaitMillis(long maxWaitMillis) {
        this.maxWaitMillis = maxWaitMillis;
        if (connectionPool != null) {
            connectionPool.setMaxWaitMillis(maxWaitMillis);
        }
    }

    /**
     * Prepared statement pooling for this pool. When this property is set to <code>true</code>
     * both PreparedStatements and CallableStatements are pooled.
     */
    private boolean poolPreparedStatements = false;

    /**
     * Returns true if we are pooling statements.
     *
     * @return true if prepared and callable statements are pooled
     */
    @Override
    public synchronized boolean isPoolPreparedStatements() {
        return this.poolPreparedStatements;
    }

    /**
     * <p>Sets whether to pool statements or not.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param poolingStatements pooling on or off
     */
    public synchronized void setPoolPreparedStatements(boolean poolingStatements) {
        this.poolPreparedStatements = poolingStatements;
    }

    /**
     * <p>The maximum number of open statements that can be allocated from
     * the statement pool at the same time, or negative for no limit.  Since
     * a connection usually only uses one or two statements at a time, this is
     * mostly used to help detect resource leaks.</p>
     *
     * <p>Note: As of version 1.3, CallableStatements (those produced by {@link Connection#prepareCall})
     * are pooled along with PreparedStatements (produced by {@link Connection#prepareStatement})
     * and <code>maxOpenPreparedStatements</code> limits the total number of prepared or callable statements
     * that may be in use at a given time.</p>
     */
    private int maxOpenPreparedStatements =
        GenericKeyedObjectPoolConfig.DEFAULT_MAX_TOTAL;

    /**
     * Gets the value of the <code>maxOpenPreparedStatements</code> property.
     *
     * @return the maximum number of open statements
     */
    @Override
    public synchronized int getMaxOpenPreparedStatements() {
        return this.maxOpenPreparedStatements;
    }

    /**
     * <p>Sets the value of the <code>maxOpenPreparedStatements</code>
     * property.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param maxOpenStatements the new maximum number of prepared statements
     */
    public synchronized void setMaxOpenPreparedStatements(int maxOpenStatements) {
        this.maxOpenPreparedStatements = maxOpenStatements;
    }

    /**
     * The indication of whether objects will be validated as soon as they have
     * been created by the pool. If the object fails to validate, the borrow
     * operation that triggered the creation will fail.
     */
    private boolean testOnCreate = false;

    /**
     * Returns the {@link #testOnCreate} property.
     *
     * @return true if objects are validated immediately after they are created
     * by the pool
     *
     * @see #testOnCreate
     */
    @Override
    public synchronized boolean getTestOnCreate() {
        return this.testOnCreate;
    }

    /**
     * Sets the {@link #testOnCreate} property. This property determines
     * whether or not the pool will validate objects immediately after they are
     * created by the pool
     *
     * @param testOnCreate new value for testOnCreate property
     */
    public synchronized void setTestOnCreate(boolean testOnCreate) {
        this.testOnCreate = testOnCreate;
        if (connectionPool != null) {
            connectionPool.setTestOnCreate(testOnCreate);
        }
    }

    /**
     * The indication of whether objects will be validated before being
     * borrowed from the pool.  If the object fails to validate, it will be
     * dropped from the pool, and we will attempt to borrow another.
     */
    private boolean testOnBorrow = true;

    /**
     * Returns the {@link #testOnBorrow} property.
     *
     * @return true if objects are validated before being borrowed from the
     * pool
     *
     * @see #testOnBorrow
     */
    @Override
    public synchronized boolean getTestOnBorrow() {
        return this.testOnBorrow;
    }

    /**
     * Sets the {@link #testOnBorrow} property. This property determines
     * whether or not the pool will validate objects before they are borrowed
     * from the pool.
     *
     * @param testOnBorrow new value for testOnBorrow property
     */
    public synchronized void setTestOnBorrow(boolean testOnBorrow) {
        this.testOnBorrow = testOnBorrow;
        if (connectionPool != null) {
            connectionPool.setTestOnBorrow(testOnBorrow);
        }
    }

    /**
     * The indication of whether objects will be validated before being
     * returned to the pool.
     */
    private boolean testOnReturn = false;

    /**
     * Returns the value of the {@link #testOnReturn} property.
     *
     * @return true if objects are validated before being returned to the
     * pool
     * @see #testOnReturn
     */
    public synchronized boolean getTestOnReturn() {
        return this.testOnReturn;
    }

    /**
     * Sets the <code>testOnReturn</code> property. This property determines
     * whether or not the pool will validate objects before they are returned
     * to the pool.
     *
     * @param testOnReturn new value for testOnReturn property
     */
    public synchronized void setTestOnReturn(boolean testOnReturn) {
        this.testOnReturn = testOnReturn;
        if (connectionPool != null) {
            connectionPool.setTestOnReturn(testOnReturn);
        }
    }

    /**
     * The number of milliseconds to sleep between runs of the idle object
     * evictor thread.  When non-positive, no idle object evictor thread will
     * be run.
     */
    private long timeBetweenEvictionRunsMillis =
        BaseObjectPoolConfig.DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;

    /**
     * Returns the value of the {@link #timeBetweenEvictionRunsMillis}
     * property.
     *
     * @return the time (in milliseconds) between evictor runs
     * @see #timeBetweenEvictionRunsMillis
     */
    @Override
    public synchronized long getTimeBetweenEvictionRunsMillis() {
        return this.timeBetweenEvictionRunsMillis;
    }

    /**
     * Sets the {@link #timeBetweenEvictionRunsMillis} property.
     *
     * @param timeBetweenEvictionRunsMillis the new time between evictor runs
     * @see #timeBetweenEvictionRunsMillis
     */
    public synchronized void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis) {
        this.timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
        if (connectionPool != null) {
            connectionPool.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        }
    }

    /**
     * The number of objects to examine during each run of the idle object
     * evictor thread (if any).
     */
    private int numTestsPerEvictionRun =
        BaseObjectPoolConfig.DEFAULT_NUM_TESTS_PER_EVICTION_RUN;

    /**
     * Returns the value of the {@link #numTestsPerEvictionRun} property.
     *
     * @return the number of objects to examine during idle object evictor
     * runs
     * @see #numTestsPerEvictionRun
     */
    @Override
    public synchronized int getNumTestsPerEvictionRun() {
        return this.numTestsPerEvictionRun;
    }

    /**
     * Sets the value of the {@link #numTestsPerEvictionRun} property.
     *
     * @param numTestsPerEvictionRun the new {@link #numTestsPerEvictionRun}
     * value
     * @see #numTestsPerEvictionRun
     */
    public synchronized void setNumTestsPerEvictionRun(int numTestsPerEvictionRun) {
        this.numTestsPerEvictionRun = numTestsPerEvictionRun;
        if (connectionPool != null) {
            connectionPool.setNumTestsPerEvictionRun(numTestsPerEvictionRun);
        }
    }

    /**
     * The minimum amount of time an object may sit idle in the pool before it
     * is eligible for eviction by the idle object evictor (if any).
     */
    private long minEvictableIdleTimeMillis =
        BaseObjectPoolConfig.DEFAULT_MIN_EVICTABLE_IDLE_TIME_MILLIS;

    /**
     * Returns the {@link #minEvictableIdleTimeMillis} property.
     *
     * @return the value of the {@link #minEvictableIdleTimeMillis} property
     * @see #minEvictableIdleTimeMillis
     */
    @Override
    public synchronized long getMinEvictableIdleTimeMillis() {
        return this.minEvictableIdleTimeMillis;
    }

    /**
     * Sets the {@link #minEvictableIdleTimeMillis} property.
     *
     * @param minEvictableIdleTimeMillis the minimum amount of time an object
     * may sit idle in the pool
     * @see #minEvictableIdleTimeMillis
     */
    public synchronized void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis) {
        this.minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
        if (connectionPool != null) {
            connectionPool.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        }
    }

    /**
     * The minimum amount of time a connection may sit idle in the pool before
     * it is eligible for eviction by the idle object evictor, with the extra
     * condition that at least "minIdle" connections remain in the pool.
     * Note that {@code minEvictableIdleTimeMillis} takes precedence over this
     * parameter.  See {@link #getSoftMinEvictableIdleTimeMillis()}.
     */
    private long softMinEvictableIdleTimeMillis =
        BaseObjectPoolConfig.DEFAULT_SOFT_MIN_EVICTABLE_IDLE_TIME_MILLIS;

    /**
     * Sets the minimum amount of time a connection may sit idle in the pool
     * before it is eligible for eviction by the idle object evictor, with the
     * extra condition that at least "minIdle" connections remain in the pool.
     *
     * @param softMinEvictableIdleTimeMillis minimum amount of time a
     * connection may sit idle in the pool before it is eligible for eviction,
     * assuming there are minIdle idle connections in the pool.
     * @see #getSoftMinEvictableIdleTimeMillis
     */
    public synchronized void setSoftMinEvictableIdleTimeMillis(long softMinEvictableIdleTimeMillis) {
        this.softMinEvictableIdleTimeMillis = softMinEvictableIdleTimeMillis;
        if (connectionPool != null) {
            connectionPool.setSoftMinEvictableIdleTimeMillis(softMinEvictableIdleTimeMillis);
        }
    }

    /**
     * <p>Returns the minimum amount of time a connection may sit idle in the
     * pool before it is eligible for eviction by the idle object evictor, with
     * the extra condition that at least "minIdle" connections remain in the
     * pool.</p>
     *
     * <p>When {@link #getMinEvictableIdleTimeMillis() miniEvictableIdleTimeMillis}
     * is set to a positive value, miniEvictableIdleTimeMillis is examined
     * first by the idle connection evictor - i.e. when idle connections are
     * visited by the evictor, idle time is first compared against
     * {@code minEvictableIdleTimeMillis} (without considering the number of idle
     * connections in the pool) and then against
     * {@code softMinEvictableIdleTimeMillis}, including the {@code minIdle},
     * constraint.</p>
     *
     * @return minimum amount of time a connection may sit idle in the pool before
     * it is eligible for eviction, assuming there are minIdle idle connections
     * in the pool
     */
    @Override
    public synchronized long getSoftMinEvictableIdleTimeMillis() {
        return softMinEvictableIdleTimeMillis;
    }

    private String evictionPolicyClassName =
            BaseObjectPoolConfig.DEFAULT_EVICTION_POLICY_CLASS_NAME;

    /**
     * Gets the EvictionPolicy implementation in use with this connection pool.
     */
    public synchronized String getEvictionPolicyClassName() {
        return evictionPolicyClassName;
    }

    /**
     * Sets the EvictionPolicy implementation to use with this connection pool.
     *
     * @param evictionPolicyClassName   The fully qualified class name of the
     *                                  EvictionPolicy implementation
     */
    public synchronized void setEvictionPolicyClassName(
            String evictionPolicyClassName) {
        if (connectionPool != null) {
            connectionPool.setEvictionPolicyClassName(evictionPolicyClassName);
        }
        this.evictionPolicyClassName = evictionPolicyClassName;
    }

    /**
     * The indication of whether objects will be validated by the idle object
     * evictor (if any).  If an object fails to validate, it will be dropped
     * from the pool.
     */
    private boolean testWhileIdle = false;

    /**
     * Returns the value of the {@link #testWhileIdle} property.
     *
     * @return true if objects examined by the idle object evictor are
     * validated
     * @see #testWhileIdle
     */
    @Override
    public synchronized boolean getTestWhileIdle() {
        return this.testWhileIdle;
    }

    /**
     * Sets the <code>testWhileIdle</code> property. This property determines
     * whether or not the idle object evictor will validate connections.
     *
     * @param testWhileIdle new value for testWhileIdle property
     */
    public synchronized void setTestWhileIdle(boolean testWhileIdle) {
        this.testWhileIdle = testWhileIdle;
        if (connectionPool != null) {
            connectionPool.setTestWhileIdle(testWhileIdle);
        }
    }

    /**
     * [Read Only] The current number of active connections that have been
     * allocated from this data source.
     *
     * @return the current number of active connections
     */
    @Override
    public synchronized int getNumActive() {
        if (connectionPool != null) {
            return connectionPool.getNumActive();
        }
        return 0;
    }


    /**
     * [Read Only] The current number of idle connections that are waiting
     * to be allocated from this data source.
     *
     * @return the current number of idle connections
     */
    @Override
    public synchronized int getNumIdle() {
        if (connectionPool != null) {
            return connectionPool.getNumIdle();
        }
        return 0;
    }

    /**
     * The connection password to be passed to our JDBC driver to establish
     * a connection.
     */
    private volatile String password = null;

    /**
     * Returns the password passed to the JDBC driver to establish connections.
     *
     * @return the connection password
     */
    @Override
    public String getPassword() {
        return this.password;
    }

    /**
     * <p>Sets the {@link #password}.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param password new value for the password
     */
    public void setPassword(String password) {
        this.password = password;
    }

    /**
     * The connection URL to be passed to our JDBC driver to establish
     * a connection.
     */
    private String url = null;

    /**
     * Returns the JDBC connection {@link #url} property.
     *
     * @return the {@link #url} passed to the JDBC driver to establish
     * connections
     */
    @Override
    public synchronized String getUrl() {
        return this.url;
    }

    /**
     * <p>Sets the {@link #url}.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param url the new value for the JDBC connection url
     */
    public synchronized void setUrl(String url) {
        this.url = url;
    }

    /**
     * The connection username to be passed to our JDBC driver to
     * establish a connection.
     */
    private String username = null;

    /**
     * Returns the JDBC connection {@link #username} property.
     *
     * @return the {@link #username} passed to the JDBC driver to establish
     * connections
     */
    @Override
    public String getUsername() {
        return this.username;
    }

    /**
     * <p>Sets the {@link #username}.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param username the new value for the JDBC connection username
     */
    public void setUsername(String username) {
        this.username = username;
    }

    /**
     * The SQL query that will be used to validate connections from this pool
     * before returning them to the caller.  If specified, this query
     * <strong>MUST</strong> be an SQL SELECT statement that returns at least
     * one row. If not specified, {@link Connection#isValid(int)} will be used
     * to validate connections.
     */
    private volatile String validationQuery = null;

    /**
     * Returns the validation query used to validate connections before
     * returning them.
     *
     * @return the SQL validation query
     * @see #validationQuery
     */
    @Override
    public String getValidationQuery() {
        return this.validationQuery;
    }

    /**
     * <p>Sets the {@link #validationQuery}.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param validationQuery the new value for the validation query
     */
    public void setValidationQuery(String validationQuery) {
        if (validationQuery != null && validationQuery.trim().length() > 0) {
            this.validationQuery = validationQuery;
        } else {
            this.validationQuery = null;
        }
    }

    /**
     * Timeout in seconds before connection validation queries fail.
     */
    private volatile int validationQueryTimeout = -1;

    /**
     * Returns the validation query timeout.
     *
     * @return the timeout in seconds before connection validation queries fail.
     */
    @Override
    public int getValidationQueryTimeout() {
        return validationQueryTimeout;
    }

    /**
     * Sets the validation query timeout, the amount of time, in seconds, that
     * connection validation will wait for a response from the database when
     * executing a validation query.  Use a value less than or equal to 0 for
     * no timeout.
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param timeout new validation query timeout value in seconds
     */
    public void setValidationQueryTimeout(int timeout) {
        this.validationQueryTimeout = timeout;
    }

    /**
     * These SQL statements run once after a Connection is created.
     * <p>
     * This property can be used for example to run ALTER SESSION SET
     * NLS_SORT=XCYECH in an Oracle Database only once after connection
     * creation.
     * </p>
     */
    private volatile List<String> connectionInitSqls;

    /**
     * Returns the list of SQL statements executed when a physical connection
     * is first created. Returns an empty list if there are no initialization
     * statements configured.
     *
     * @return initialization SQL statements
     */
    public List<String> getConnectionInitSqls() {
        List<String> result = connectionInitSqls;
        if (result == null) {
            return Collections.emptyList();
        }
        return result;
    }

    /**
     * Provides the same data as {@link #getConnectionInitSqls()} but in an
     * array so it is accessible via JMX.
     */
    @Override
    public String[] getConnectionInitSqlsAsArray() {
        Collection<String> result = getConnectionInitSqls();
        return result.toArray(new String[result.size()]);
    }

    /**
     * Sets the list of SQL statements to be executed when a physical
     * connection is first created.
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param connectionInitSqls Collection of SQL statements to execute
     * on connection creation
     */
    public void setConnectionInitSqls(Collection<String> connectionInitSqls) {
        if (connectionInitSqls != null && connectionInitSqls.size() > 0) {
            ArrayList<String> newVal = null;
            for (String s : connectionInitSqls) {
            if (s != null && s.trim().length() > 0) {
                    if (newVal == null) {
                        newVal = new ArrayList<>();
                    }
                    newVal.add(s);
                }
            }
            this.connectionInitSqls = newVal;
        } else {
            this.connectionInitSqls = null;
        }
    }


    /**
     * Controls access to the underlying connection.
     */
    private boolean accessToUnderlyingConnectionAllowed = false;

    /**
     * Returns the value of the accessToUnderlyingConnectionAllowed property.
     *
     * @return true if access to the underlying connection is allowed, false
     * otherwise.
     */
    @Override
    public synchronized boolean isAccessToUnderlyingConnectionAllowed() {
        return this.accessToUnderlyingConnectionAllowed;
    }

    /**
     * <p>Sets the value of the accessToUnderlyingConnectionAllowed property.
     * It controls if the PoolGuard allows access to the underlying connection.
     * (Default: false)</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     *
     * @param allow Access to the underlying connection is granted when true.
     */
    public synchronized void setAccessToUnderlyingConnectionAllowed(boolean allow) {
        this.accessToUnderlyingConnectionAllowed = allow;
    }


    private long maxConnLifetimeMillis = -1;

    /**
     * Returns the maximum permitted lifetime of a connection in milliseconds. A
     * value of zero or less indicates an infinite lifetime.
     */
    @Override
    public long getMaxConnLifetimeMillis() {
        return maxConnLifetimeMillis;
    }

    /**
     * <p>Sets the maximum permitted lifetime of a connection in
     * milliseconds. A value of zero or less indicates an infinite lifetime.</p>
     * <p>
     * Note: this method currently has no effect once the pool has been
     * initialized.  The pool is initialized the first time one of the
     * following methods is invoked: <code>getConnection, setLogwriter,
     * setLoginTimeout, getLoginTimeout, getLogWriter.</code></p>
     */
    public void setMaxConnLifetimeMillis(long maxConnLifetimeMillis) {
        this.maxConnLifetimeMillis = maxConnLifetimeMillis;
    }

    private String jmxName = null;

    /**
     * Returns the JMX name that has been requested for this DataSource. If the
     * requested name is not valid, an alternative may be chosen.
     */
    public String getJmxName() {
        return jmxName;
    }

    /**
     * Sets the JMX name that has been requested for this DataSource. If the
     * requested name is not valid, an alternative may be chosen. This
     * DataSource will attempt to register itself using this name. If another
     * component registers this DataSource with JMX and this name is valid this
     * name will be used in preference to any specified by the other component.
     */
    public void setJmxName(String jmxName) {
        this.jmxName = jmxName;
    }


    private boolean enableAutoCommitOnReturn = true;

    /**
     * Returns the value of the flag that controls whether or not connections
     * being returned to the pool will checked and configured with
     * {@link Connection#setAutoCommit(boolean) Connection.setAutoCommit(true)}
     * if the auto commit setting is {@code false} when the connection
     * is returned. It is <code>true</code> by default.
     */
    public boolean getEnableAutoCommitOnReturn() {
        return enableAutoCommitOnReturn;
    }

    /**
     * Sets the value of the flag that controls whether or not connections
     * being returned to the pool will checked and configured with
     * {@link Connection#setAutoCommit(boolean) Connection.setAutoCommit(true)}
     * if the auto commit setting is {@code false} when the connection
     * is returned. It is <code>true</code> by default.
     */
    public void setEnableAutoCommitOnReturn(boolean enableAutoCommitOnReturn) {
        this.enableAutoCommitOnReturn = enableAutoCommitOnReturn;
    }


    private boolean rollbackOnReturn = true;

    /**
     * Gets the current value of the flag that controls if a connection will be
     * rolled back when it is returned to the pool if auto commit is not enabled
     * and the connection is not read only.
     */
    public boolean getRollbackOnReturn() {
        return rollbackOnReturn;
    }

    /**
     * Sets the flag that controls if a connection will be rolled back when it
     * is returned to the pool if auto commit is not enabled and the connection
     * is not read only.
     */
    public void setRollbackOnReturn(boolean rollbackOnReturn) {
        this.rollbackOnReturn = rollbackOnReturn;
    }


    // ----------------------------------------------------- Instance Variables

    /**
     * The object pool that internally manages our connections.
     */
    private volatile GenericObjectPool<PoolableConnection> connectionPool = null;

    protected GenericObjectPool<PoolableConnection> getConnectionPool() {
        return connectionPool;
    }

    /**
     * The connection properties that will be sent to our JDBC driver when
     * establishing new connections.  <strong>NOTE</strong> - The "user" and
     * "password" properties will be passed explicitly, so they do not need
     * to be included here.
     */
    private Properties connectionProperties = new Properties();

    // For unit testing
    Properties getConnectionProperties() {
        return connectionProperties;
    }

    /**
     * The data source we will use to manage connections.  This object should
     * be acquired <strong>ONLY</strong> by calls to the
     * <code>createDataSource()</code> method.
     */
    private volatile DataSource dataSource = null;

    /**
     * The PrintWriter to which log messages should be directed.
     */
    private volatile PrintWriter logWriter = new PrintWriter(new OutputStreamWriter(
            System.out, StandardCharsets.UTF_8));


    // ----------------------------------------------------- DataSource Methods


    /**
     * Create (if necessary) and return a connection to the database.
     *
     * @throws SQLException if a database access error occurs
     * @return a database connection
     */
    @Override
    public Connection getConnection() throws SQLException {
        if (Utils.IS_SECURITY_ENABLED) {
            PrivilegedExceptionAction<Connection> action = new PaGetConnection();
            try {
                return AccessController.doPrivileged(action);
            } catch (PrivilegedActionException e) {
                Throwable cause = e.getCause();
                if (cause instanceof SQLException) {
                    throw (SQLException) cause;
                }
                throw new SQLException(e);
            }
        }
        return createDataSource().getConnection();
    }


    /**
     * <strong>BasicDataSource does NOT support this method. </strong>
     *
     * @param user Database user on whose behalf the Connection
     *   is being made
     * @param pass The database user's password
     *
     * @throws UnsupportedOperationException
     * @throws SQLException if a database access error occurs
     * @return nothing - always throws UnsupportedOperationException
     */
    @Override
    public Connection getConnection(String user, String pass) throws SQLException {
        // This method isn't supported by the PoolingDataSource returned by
        // the createDataSource
        throw new UnsupportedOperationException("Not supported by BasicDataSource");
    }


    /**
     * <strong>BasicDataSource does NOT support this method. </strong>
     *
     * <p>Returns the login timeout (in seconds) for connecting to the database.
     * </p>
     * <p>Calls {@link #createDataSource()}, so has the side effect
     * of initializing the connection pool.</p>
     *
     * @throws SQLException if a database access error occurs
     * @throws UnsupportedOperationException If the DataSource implementation
     *   does not support the login timeout feature.
     * @return login timeout in seconds
     */
    @Override
    public int getLoginTimeout() throws SQLException {
        // This method isn't supported by the PoolingDataSource returned by
        // the createDataSource
        throw new UnsupportedOperationException("Not supported by BasicDataSource");
    }


    /**
     * <p>Returns the log writer being used by this data source.</p>
     * <p>
     * Calls {@link #createDataSource()}, so has the side effect
     * of initializing the connection pool.</p>
     *
     * @throws SQLException if a database access error occurs
     * @return log writer in use
     */
    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return createDataSource().getLogWriter();
    }


    /**
     * <strong>BasicDataSource does NOT support this method. </strong>
     *
     * <p>Set the login timeout (in seconds) for connecting to the
     * database.</p>
     * <p>
     * Calls {@link #createDataSource()}, so has the side effect
     * of initializing the connection pool.</p>
     *
     * @param loginTimeout The new login timeout, or zero for no timeout
     * @throws UnsupportedOperationException If the DataSource implementation
     *   does not support the login timeout feature.
     * @throws SQLException if a database access error occurs
     */
    @Override
    public void setLoginTimeout(int loginTimeout) throws SQLException {
        // This method isn't supported by the PoolingDataSource returned by
        // the createDataSource
        throw new UnsupportedOperationException("Not supported by BasicDataSource");
    }


    /**
     * <p>Sets the log writer being used by this data source.</p>
     * <p>
     * Calls {@link #createDataSource()}, so has the side effect
     * of initializing the connection pool.</p>
     *
     * @param logWriter The new log writer
     * @throws SQLException if a database access error occurs
     */
    @Override
    public void setLogWriter(PrintWriter logWriter) throws SQLException {
        createDataSource().setLogWriter(logWriter);
        this.logWriter = logWriter;
    }

    private AbandonedConfig abandonedConfig;

    /**
     * <p>Flag to remove abandoned connections if they exceed the
     * removeAbandonedTimeout when borrowObject is invoked.</p>
     *
     * <p>The default value is false.<p>
     *
     * <p>If set to true a connection is considered abandoned and eligible
     * for removal if it has not been used for more than
     * {@link #getRemoveAbandonedTimeout() removeAbandonedTimeout} seconds.</p>
     *
     * <p>Abandoned connections are identified and removed when
     * {@link #getConnection()} is invoked and the following conditions hold
     * <ul><li>{@link #getRemoveAbandonedOnBorrow()} or
     *         {@link #getRemoveAbandonedOnMaintenance()} = true</li>
     *     <li>{@link #getNumActive()} > {@link #getMaxTotal()} - 3 </li>
     *     <li>{@link #getNumIdle()} < 2 </li></ul></p>
     *
     * @see #getRemoveAbandonedTimeout()
     */
    @Override
    public boolean getRemoveAbandonedOnBorrow() {
        if (abandonedConfig != null) {
            return abandonedConfig.getRemoveAbandonedOnBorrow();
        }
        return false;
    }

    /**
     * <p>Flag to remove abandoned connections if they exceed the
     * removeAbandonedTimeout when borrowObject is invoked.</p>
     *
     * <p>If set to true a connection is considered abandoned and eligible
     * for removal if it has been idle longer than the
     * {@link #getRemoveAbandonedTimeout() removeAbandonedTimeout}.</p>
     *
     * <p>Setting this to true can recover db connections from poorly written
     * applications which fail to close a connection.</p>
     *
     * @param removeAbandonedOnMaintenance true means abandoned connections will
     *                                     be removed when borrowObject is
     *                                     invoked
     */
    public void setRemoveAbandonedOnMaintenance(
            boolean removeAbandonedOnMaintenance) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setRemoveAbandonedOnMaintenance(
                removeAbandonedOnMaintenance);
    }

    /**
     * <p>Flag to remove abandoned connections if they exceed the
     * removeAbandonedTimeout during pool maintenance.</p>
     *
     * <p>The default value is false.<p>
     *
     * <p>If set to true a connection is considered abandoned and eligible
     * for removal if it has not been used for more than
     * {@link #getRemoveAbandonedTimeout() removeAbandonedTimeout} seconds.</p>
     *
     * <p>Abandoned connections are identified and removed when
     * {@link #getConnection()} is invoked and the following conditions hold
     * <ul><li>{@link #getRemoveAbandonedOnBorrow()} or
     *         {@link #getRemoveAbandonedOnMaintenance()} = true</li>
     *     <li>{@link #getNumActive()} > {@link #getMaxTotal()} - 3 </li>
     *     <li>{@link #getNumIdle()} < 2 </li></ul></p>
     *
     * @see #getRemoveAbandonedTimeout()
     */
    @Override
    public boolean getRemoveAbandonedOnMaintenance() {
        if (abandonedConfig != null) {
            return abandonedConfig.getRemoveAbandonedOnMaintenance();
        }
        return false;
    }

    /**
     * <p>Flag to remove abandoned connections if they exceed the
     * removeAbandonedTimeout during pool maintenance.</p>
     *
     * <p>If set to true a connection is considered abandoned and eligible
     * for removal if it has been idle longer than the
     * {@link #getRemoveAbandonedTimeout() removeAbandonedTimeout}.</p>
     *
     * <p>Setting this to true can recover db connections from poorly written
     * applications which fail to close a connection.</p>
     *
     * @param removeAbandonedOnBorrow true means abandoned connections will be
     *                                removed during pool maintenance
     */
    public void setRemoveAbandonedOnBorrow(boolean removeAbandonedOnBorrow) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setRemoveAbandonedOnBorrow(removeAbandonedOnBorrow);
    }

    /**
     * <p>Timeout in seconds before an abandoned connection can be removed.</p>
     *
     * <p>Creating a Statement, PreparedStatement or CallableStatement or using
     * one of these to execute a query (using one of the execute methods)
     * resets the lastUsed property of the parent connection.</p>
     *
     * <p>Abandoned connection cleanup happens when
     * <code><ul>
     * <li>{@link #getRemoveAbandonedOnBorrow()} or
     *     {@link #getRemoveAbandonedOnMaintenance()} = true</li>
     * <li>{@link #getNumIdle() numIdle} &lt; 2</li>
     * <li>{@link #getNumActive() numActive} &gt; {@link #getMaxTotal() maxTotal} - 3</li>
     * </ul></code></p>
     *
     * <p>The default value is 300 seconds.</p>
     */
    @Override
    public int getRemoveAbandonedTimeout() {
        if (abandonedConfig != null) {
            return abandonedConfig.getRemoveAbandonedTimeout();
        }
        return 300;
    }

    /**
     * <p>Sets the timeout in seconds before an abandoned connection can be
     * removed.</p>
     *
     * <p>Setting this property has no effect if
     * {@link #getRemoveAbandonedOnBorrow()} and
     * {@link #getRemoveAbandonedOnMaintenance()} are false.</p>
     *
     * @param removeAbandonedTimeout new abandoned timeout in seconds
     * @see #getRemoveAbandonedTimeout()
     * @see #getRemoveAbandonedOnBorrow()
     * @see #getRemoveAbandonedOnMaintenance()
     */
    public void setRemoveAbandonedTimeout(int removeAbandonedTimeout) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setRemoveAbandonedTimeout(removeAbandonedTimeout);
    }

    /**
     * <p>Flag to log stack traces for application code which abandoned
     * a Statement or Connection.
     * </p>
     * <p>Defaults to false.
     * </p>
     * <p>Logging of abandoned Statements and Connections adds overhead
     * for every Connection open or new Statement because a stack
     * trace has to be generated. </p>
     */
    @Override
    public boolean getLogAbandoned() {
        if (abandonedConfig != null) {
            return abandonedConfig.getLogAbandoned();
        }
        return false;
    }

    /**
     * @param logAbandoned new logAbandoned property value
     */
    public void setLogAbandoned(boolean logAbandoned) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setLogAbandoned(logAbandoned);
    }

    /**
     * Gets the log writer to be used by this configuration to log
     * information on abandoned objects.
     */
    public PrintWriter getAbandonedLogWriter() {
        if (abandonedConfig != null) {
            return abandonedConfig.getLogWriter();
        }
        return null;
    }

    /**
     * Sets the log writer to be used by this configuration to log
     * information on abandoned objects.
     *
     * @param logWriter The new log writer
     */
    public void setAbandonedLogWriter(PrintWriter logWriter) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setLogWriter(logWriter);
    }

    /**
     * If the connection pool implements {@link org.apache.tomcat.dbcp.pool2.UsageTracking UsageTracking}, should the
     * connection pool record a stack trace every time a method is called on a
     * pooled connection and retain the most recent stack trace to aid debugging
     * of abandoned connections?
     *
     * @return <code>true</code> if usage tracking is enabled
     */
    @Override
    public boolean getAbandonedUsageTracking() {
        if (abandonedConfig != null) {
            return abandonedConfig.getUseUsageTracking();
        }
        return false;
    }

    /**
     * If the connection pool implements {@link org.apache.tomcat.dbcp.pool2.UsageTracking UsageTracking}, configure
     * whether the connection pool should record a stack trace every time a
     * method is called on a pooled connection and retain the most recent stack
     * trace to aid debugging of abandoned connections.
     *
     * @param   usageTracking    A value of <code>true</code> will enable
     *                              the recording of a stack trace on every use
     *                              of a pooled connection
     */
    public void setAbandonedUsageTracking(boolean usageTracking) {
        if (abandonedConfig == null) {
            abandonedConfig = new AbandonedConfig();
        }
        abandonedConfig.setUseUsageTracking(usageTracking);
    }

    // --------------------------------------------------------- Public Methods

    /**
     * Add a custom connection property to the set that will be passed to our
     * JDBC driver. This <strong>MUST</strong> be called before the first
     * connection is retrieved (along with all the other configuration
     * property setters). Calls to this method after the connection pool
     * has been initialized have no effect.
     *
     * @param name Name of the custom connection property
     * @param value Value of the custom connection property
     */
    public void addConnectionProperty(String name, String value) {
        connectionProperties.put(name, value);
    }

    /**
     * Remove a custom connection property.
     *
     * @param name Name of the custom connection property to remove
     * @see #addConnectionProperty(String, String)
     */
    public void removeConnectionProperty(String name) {
        connectionProperties.remove(name);
    }

    /**
     * Sets the connection properties passed to driver.connect(...).
     *
     * Format of the string must be [propertyName=property;]*
     *
     * NOTE - The "user" and "password" properties will be added
     * explicitly, so they do not need to be included here.
     *
     * @param connectionProperties the connection properties used to
     * create new connections
     */
    public void setConnectionProperties(String connectionProperties) {
        if (connectionProperties == null) {
            throw new NullPointerException("connectionProperties is null");
        }

        String[] entries = connectionProperties.split(";");
        Properties properties = new Properties();
        for (String entry : entries) {
            if (entry.length() > 0) {
                int index = entry.indexOf('=');
                if (index > 0) {
                    String name = entry.substring(0, index);
                    String value = entry.substring(index + 1);
                    properties.setProperty(name, value);
                } else {
                    // no value is empty string which is how java.util.Properties works
                    properties.setProperty(entry, "");
                }
            }
        }
        this.connectionProperties = properties;
    }

    private boolean closed;

    /**
     * <p>Closes and releases all idle connections that are currently stored in the connection pool
     * associated with this data source.</p>
     *
     * <p>Connections that are checked out to clients when this method is invoked are not affected.
     * When client applications subsequently invoke {@link Connection#close()} to return
     * these connections to the pool, the underlying JDBC connections are closed.</p>
     *
     * <p>Attempts to acquire connections using {@link #getConnection()} after this method has been
     * invoked result in SQLExceptions.<p>
     *
     * <p>This method is idempotent - i.e., closing an already closed BasicDataSource has no effect
     * and does not generate exceptions.</p>
     *
     * @throws SQLException if an error occurs closing idle connections
     */
    public synchronized void close() throws SQLException {
        if (registeredJmxName != null) {
            MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
            try {
                mbs.unregisterMBean(registeredJmxName);
            } catch (JMException e) {
                log.warn("Failed to unregister the JMX name: " + registeredJmxName, e);
            } finally {
                registeredJmxName = null;
            }
        }
        closed = true;
        GenericObjectPool<?> oldpool = connectionPool;
        connectionPool = null;
        dataSource = null;
        try {
            if (oldpool != null) {
                oldpool.close();
            }
        } catch(RuntimeException e) {
            throw e;
        } catch(Exception e) {
            throw new SQLException("Cannot close connection pool", e);
        }
    }

    /**
     * If true, this data source is closed and no more connections can be retrieved from this datasource.
     * @return true, if the data source is closed; false otherwise
     */
    @Override
    public synchronized boolean isClosed() {
        return closed;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        throw new SQLException("BasicDataSource is not a wrapper.");
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        throw new SQLFeatureNotSupportedException();
    }

    // ------------------------------------------------------ Protected Methods


    /**
     * <p>Create (if necessary) and return the internal data source we are
     * using to manage our connections.</p>
     *
     * @throws SQLException if the object pool cannot be created.
     */
    protected DataSource createDataSource()
        throws SQLException {
        if (closed) {
            throw new SQLException("Data source is closed");
        }

        // Return the pool if we have already created it
        // This is double-checked locking. This is safe since dataSource is
        // volatile and the code is targeted at Java 5 onwards.
        if (dataSource != null) {
            return dataSource;
        }
        synchronized (this) {
            if (dataSource != null) {
                return dataSource;
            }

            jmxRegister();

            // create factory which returns raw physical connections
            ConnectionFactory driverConnectionFactory = createConnectionFactory();

            // Set up the poolable connection factory
            boolean success = false;
            PoolableConnectionFactory poolableConnectionFactory;
            try {
                poolableConnectionFactory = createPoolableConnectionFactory(
                        driverConnectionFactory);
                poolableConnectionFactory.setPoolStatements(
                        poolPreparedStatements);
                poolableConnectionFactory.setMaxOpenPrepatedStatements(
                        maxOpenPreparedStatements);
                success = true;
            } catch (SQLException se) {
                throw se;
            } catch (RuntimeException rte) {
                throw rte;
            } catch (Exception ex) {
                throw new SQLException("Error creating connection factory", ex);
            }

            if (success) {
                // create a pool for our connections
                createConnectionPool(poolableConnectionFactory);
            }

            // Create the pooling data source to manage connections
            success = false;
            try {
                dataSource = createDataSourceInstance();
                dataSource.setLogWriter(logWriter);
                success = true;
            } catch (SQLException se) {
                throw se;
            } catch (RuntimeException rte) {
                throw rte;
            } catch (Exception ex) {
                throw new SQLException("Error creating datasource", ex);
            } finally {
                if (!success) {
                    closeConnectionPool();
                }
            }

            // If initialSize > 0, preload the pool
            try {
                for (int i = 0 ; i < initialSize ; i++) {
                    connectionPool.addObject();
                }
            } catch (Exception e) {
                closeConnectionPool();
                throw new SQLException("Error preloading the connection pool", e);
            }

            // If timeBetweenEvictionRunsMillis > 0, start the pool's evictor task
            startPoolMaintenance();

            return dataSource;
        }
    }

    /**
     * Creates a JDBC connection factory for this datasource.  The JDBC driver
     * is loaded using the following algorithm:
     * <ol>
     * <li>If a Driver instance has been specified via
     * {@link #setDriver(Driver)} use it</li>
     * <li>If no Driver instance was specified and {@link #driverClassName} is
     * specified that class is loaded using the {@link ClassLoader} of this
     * class or, if {@link #driverClassLoader} is set, {@link #driverClassName}
     * is loaded with the specified {@link ClassLoader}.</li>
     * <li>If {@link #driverClassName} is specified and the previous attempt
     * fails, the class is loaded using the context class loader of the current
     * thread.</li>
     * <li>If a driver still isn't loaded one is loaded via the
     * {@link DriverManager} using the specified {@link #url}.
     * </ol>
     * This method exists so subclasses can replace the implementation class.
     */
    protected ConnectionFactory createConnectionFactory() throws SQLException {
        // Load the JDBC driver class
        Driver driverToUse = this.driver;

        if (driverToUse == null) {
            Class<?> driverFromCCL = null;
            if (driverClassName != null) {
                try {
                    try {
                        if (driverClassLoader == null) {
                            driverFromCCL = Class.forName(driverClassName);
                        } else {
                            driverFromCCL = Class.forName(
                                    driverClassName, true, driverClassLoader);
                        }
                    } catch (ClassNotFoundException cnfe) {
                        driverFromCCL = Thread.currentThread(
                                ).getContextClassLoader().loadClass(
                                        driverClassName);
                    }
                } catch (Exception t) {
                    String message = "Cannot load JDBC driver class '" +
                        driverClassName + "'";
                    logWriter.println(message);
                    t.printStackTrace(logWriter);
                    throw new SQLException(message, t);
                }
            }

            try {
                if (driverFromCCL == null) {
                    driverToUse = DriverManager.getDriver(url);
                } else {
                    // Usage of DriverManager is not possible, as it does not
                    // respect the ContextClassLoader
                    // N.B. This cast may cause ClassCastException which is handled below
                    driverToUse = (Driver) driverFromCCL.newInstance();
                    if (!driverToUse.acceptsURL(url)) {
                        throw new SQLException("No suitable driver", "08001");
                    }
                }
            } catch (Exception t) {
                String message = "Cannot create JDBC driver of class '" +
                    (driverClassName != null ? driverClassName : "") +
                    "' for connect URL '" + url + "'";
                logWriter.println(message);
                t.printStackTrace(logWriter);
                throw new SQLException(message, t);
            }
        }

        // Set up the driver connection factory we will use
        String user = username;
        if (user != null) {
            connectionProperties.put("user", user);
        } else {
            log("DBCP DataSource configured without a 'username'");
        }

        String pwd = password;
        if (pwd != null) {
            connectionProperties.put("password", pwd);
        } else {
            log("DBCP DataSource configured without a 'password'");
        }

        ConnectionFactory driverConnectionFactory =
                new DriverConnectionFactory(driverToUse, url, connectionProperties);
        return driverConnectionFactory;
    }

    /**
     * Creates a connection pool for this datasource.  This method only exists
     * so subclasses can replace the implementation class.
     *
     * This implementation configures all pool properties other than
     * timeBetweenEvictionRunsMillis.  Setting that property is deferred to
     * {@link #startPoolMaintenance()}, since setting timeBetweenEvictionRunsMillis
     * to a positive value causes {@link GenericObjectPool}'s eviction timer
     * to be started.
     */
    protected void createConnectionPool(PoolableConnectionFactory factory) {
        // Create an object pool to contain our active connections
        GenericObjectPoolConfig config = new GenericObjectPoolConfig();
        updateJmxName(config);
        GenericObjectPool<PoolableConnection> gop;
        if (abandonedConfig != null &&
                (abandonedConfig.getRemoveAbandonedOnBorrow() ||
                 abandonedConfig.getRemoveAbandonedOnMaintenance())) {
            gop = new GenericObjectPool<>(factory, config, abandonedConfig);
        }
        else {
            gop = new GenericObjectPool<>(factory, config);
        }
        gop.setMaxTotal(maxTotal);
        gop.setMaxIdle(maxIdle);
        gop.setMinIdle(minIdle);
        gop.setMaxWaitMillis(maxWaitMillis);
        gop.setTestOnCreate(testOnCreate);
        gop.setTestOnBorrow(testOnBorrow);
        gop.setTestOnReturn(testOnReturn);
        gop.setNumTestsPerEvictionRun(numTestsPerEvictionRun);
        gop.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
        gop.setTestWhileIdle(testWhileIdle);
        gop.setLifo(lifo);
        gop.setSwallowedExceptionListener(new SwallowedExceptionLogger(log));
        gop.setEvictionPolicyClassName(evictionPolicyClassName);
        factory.setPool(gop);
        connectionPool = gop;
    }

    /**
     * Closes the connection pool, silently swallowing any exception that occurs.
     */
    private void closeConnectionPool() {
        GenericObjectPool<?> oldpool = connectionPool;
        connectionPool = null;
        try {
            if (oldpool != null) {
                oldpool.close();
            }
        } catch(Exception e) {
            /* Ignore */
        }
    }

    /**
     * Starts the connection pool maintenance task, if configured.
     */
    protected void startPoolMaintenance() {
        if (connectionPool != null && timeBetweenEvictionRunsMillis > 0) {
            connectionPool.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
        }
    }

    /**
     * Creates the actual data source instance.  This method only exists so
     * that subclasses can replace the implementation class.
     *
     * @throws SQLException if unable to create a datasource instance
     */
    protected DataSource createDataSourceInstance() throws SQLException {
        PoolingDataSource<PoolableConnection> pds = new PoolingDataSource<>(connectionPool);
        pds.setAccessToUnderlyingConnectionAllowed(isAccessToUnderlyingConnectionAllowed());
        return pds;
    }

    /**
     * Creates the PoolableConnectionFactory and attaches it to the connection pool.  This method only exists
     * so subclasses can replace the default implementation.
     *
     * @param driverConnectionFactory JDBC connection factory
     * @throws SQLException if an error occurs creating the PoolableConnectionFactory
     */
    protected PoolableConnectionFactory createPoolableConnectionFactory(
            ConnectionFactory driverConnectionFactory) throws SQLException {
        PoolableConnectionFactory connectionFactory = null;
        try {
            connectionFactory = new PoolableConnectionFactory(driverConnectionFactory, registeredJmxName);
            connectionFactory.setValidationQuery(validationQuery);
            connectionFactory.setValidationQueryTimeout(validationQueryTimeout);
            connectionFactory.setConnectionInitSql(connectionInitSqls);
            connectionFactory.setDefaultReadOnly(defaultReadOnly);
            connectionFactory.setDefaultAutoCommit(defaultAutoCommit);
            connectionFactory.setDefaultTransactionIsolation(defaultTransactionIsolation);
            connectionFactory.setDefaultCatalog(defaultCatalog);
            connectionFactory.setCacheState(cacheState);
            connectionFactory.setPoolStatements(poolPreparedStatements);
            connectionFactory.setMaxOpenPrepatedStatements(maxOpenPreparedStatements);
            connectionFactory.setMaxConnLifetimeMillis(maxConnLifetimeMillis);
            connectionFactory.setRollbackOnReturn(getRollbackOnReturn());
            connectionFactory.setEnableAutoCommitOnReturn(getEnableAutoCommitOnReturn());
            connectionFactory.setDefaultQueryTimeout(getDefaultQueryTimeout());
            validateConnectionFactory(connectionFactory);
        } catch (RuntimeException e) {
            throw e;
        } catch (Exception e) {
            throw new SQLException("Cannot create PoolableConnectionFactory (" + e.getMessage() + ")", e);
        }
        return connectionFactory;
    }

    protected static void validateConnectionFactory(
            PoolableConnectionFactory connectionFactory) throws Exception {
        PoolableConnection conn = null;
        PooledObject<PoolableConnection> p = null;
        try {
            p = connectionFactory.makeObject();
            conn = p.getObject();
            connectionFactory.activateObject(p);
            connectionFactory.validateConnection(conn);
            connectionFactory.passivateObject(p);
        }
        finally {
            if (p != null) {
                connectionFactory.destroyObject(p);
            }
        }
    }

    protected void log(String message) {
        if (logWriter != null) {
            logWriter.println(message);
        }
    }

    /**
     * Actual name under which this component has been registered.
     */
    private ObjectName registeredJmxName = null;

    private void jmxRegister() {
        // Return immediately if this DataSource has already been registered
        if (registeredJmxName != null) {
            return;
        }
        // Return immediately if no JMX name has been specified
        String requestedName = getJmxName();
        if (requestedName == null) {
            return;
        }
        ObjectName oname;
        try {
             oname = new ObjectName(requestedName);
        } catch (MalformedObjectNameException e) {
            log.warn("The requested JMX name [" + requestedName +
                    "] was not valid and will be ignored.");
            return;
        }

        MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        try {
            mbs.registerMBean(this, oname);
        } catch (InstanceAlreadyExistsException | MBeanRegistrationException
                | NotCompliantMBeanException e) {
            log.warn("Failed to complete JMX registration", e);
        }
    }

    @Override
    public ObjectName preRegister(MBeanServer server, ObjectName name) {
        String requestedName = getJmxName();
        if (requestedName != null) {
            try {
                registeredJmxName = new ObjectName(requestedName);
            } catch (MalformedObjectNameException e) {
                log.warn("The requested JMX name [" + requestedName +
                        "] was not valid and will be ignored.");
            }
        }
        if (registeredJmxName == null) {
            registeredJmxName = name;
        }
        return registeredJmxName;
    }

    @Override
    public void postRegister(Boolean registrationDone) {
        // NO-OP
    }

    @Override
    public void preDeregister() throws Exception {
        // NO-OP
    }

    @Override
    public void postDeregister() {
        // NO-OP
    }

    private void updateJmxName(GenericObjectPoolConfig config) {
        if (registeredJmxName == null) {
            return;
        }
        StringBuilder base = new StringBuilder(registeredJmxName.toString());
        base.append(Constants.JMX_CONNECTION_POOL_BASE_EXT);
        config.setJmxNameBase(base.toString());
        config.setJmxNamePrefix(Constants.JMX_CONNECTION_POOL_PREFIX);
    }

    protected ObjectName getRegisteredJmxName() {
        return registeredJmxName;
    }

    /**
     * @since 2.0
     */
    private class PaGetConnection implements PrivilegedExceptionAction<Connection> {

        @Override
        public Connection run() throws SQLException {
            return createDataSource().getConnection();
        }
    }
}