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/*
* 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.catalina;
import java.beans.PropertyChangeListener;
/**
* A <b>Loader</b> represents a Java ClassLoader implementation that can
* be used by a Container to load class files (within a repository associated
* with the Loader) that are designed to be reloaded upon request, as well as
* a mechanism to detect whether changes have occurred in the underlying
* repository.
* <p>
* In order for a <code>Loader</code> implementation to successfully operate
* with a <code>Context</code> implementation that implements reloading, it
* must obey the following constraints:
* <ul>
* <li>Must implement <code>Lifecycle</code> so that the Context can indicate
* that a new class loader is required.
* <li>The <code>start()</code> method must unconditionally create a new
* <code>ClassLoader</code> implementation.
* <li>The <code>stop()</code> method must throw away its reference to the
* <code>ClassLoader</code> previously utilized, so that the class loader,
* all classes loaded by it, and all objects of those classes, can be
* garbage collected.
* <li>Must allow a call to <code>stop()</code> to be followed by a call to
* <code>start()</code> on the same <code>Loader</code> instance.
* <li>Based on a policy chosen by the implementation, must call the
* <code>Context.reload()</code> method on the owning <code>Context</code>
* when a change to one or more of the class files loaded by this class
* loader is detected.
* </ul>
*
* @author Craig R. McClanahan
*/
public interface Loader {
/**
* Execute a periodic task, such as reloading, etc. This method will be
* invoked inside the classloading context of this container. Unexpected
* throwables will be caught and logged.
*/
public void backgroundProcess();
/**
* Return the Java class loader to be used by this Container.
*/
public ClassLoader getClassLoader();
/**
* Return the Context with which this Loader has been associated.
*/
public Context getContext();
/**
* Set the Context with which this Loader has been associated.
*
* @param context The associated Context
*/
public void setContext(Context context);
/**
* Return the "follow standard delegation model" flag used to configure
* our ClassLoader.
*/
public boolean getDelegate();
/**
* Set the "follow standard delegation model" flag used to configure
* our ClassLoader.
*
* @param delegate The new flag
*/
public void setDelegate(boolean delegate);
/**
* Return the reloadable flag for this Loader.
*/
public boolean getReloadable();
/**
* Set the reloadable flag for this Loader.
*
* @param reloadable The new reloadable flag
*/
public void setReloadable(boolean reloadable);
/**
* Add a property change listener to this component.
*
* @param listener The listener to add
*/
public void addPropertyChangeListener(PropertyChangeListener listener);
/**
* Has the internal repository associated with this Loader been modified,
* such that the loaded classes should be reloaded?
*/
public boolean modified();
/**
* Remove a property change listener from this component.
*
* @param listener The listener to remove
*/
public void removePropertyChangeListener(PropertyChangeListener listener);
}
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