File: ScriptFactoryPostProcessor.java

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/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed 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.springframework.scripting.support;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.objectweb.asm.Type;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.InterfaceMaker;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.aop.TargetSource;
import org.springframework.aop.framework.AopInfrastructureBean;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.support.DelegatingIntroductionInterceptor;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanCurrentlyInCreationException;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.core.Conventions;
import org.springframework.core.Ordered;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;
import org.springframework.scripting.ScriptFactory;
import org.springframework.scripting.ScriptSource;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.springframework.beans.factory.config.BeanPostProcessor} that
 * handles {@link org.springframework.scripting.ScriptFactory} definitions,
 * replacing each factory with the actual scripted Java object generated by it.
 *
 * <p>This is similar to the
 * {@link org.springframework.beans.factory.FactoryBean} mechanism, but is
 * specifically tailored for scripts and not built into Spring's core
 * container itself but rather implemented as an extension.
 *
 * <p><b>NOTE:</b> The most important characteristic of this post-processor
 * is that constructor arguments are applied to the
 * {@link org.springframework.scripting.ScriptFactory} instance
 * while bean property values are applied to the generated scripted object.
 * Typically, constructor arguments include a script source locator and
 * potentially script interfaces, while bean property values include
 * references and config values to inject into the scripted object itself.
 *
 * <p>The following {@link ScriptFactoryPostProcessor} will automatically
 * be applied to the two
 * {@link org.springframework.scripting.ScriptFactory} definitions below.
 * At runtime, the actual scripted objects will be exposed for
 * "bshMessenger" and "groovyMessenger", rather than the
 * {@link org.springframework.scripting.ScriptFactory} instances. Both of
 * those are supposed to be castable to the example's <code>Messenger</code>
 * interfaces here.
 *
 * <pre class="code">&lt;bean class="org.springframework.scripting.support.ScriptFactoryPostProcessor"/&gt;
 *
 * &lt;bean id="bshMessenger" class="org.springframework.scripting.bsh.BshScriptFactory"&gt;
 *   &lt;constructor-arg value="classpath:mypackage/Messenger.bsh"/&gt;
 *   &lt;constructor-arg value="mypackage.Messenger"/&gt;
 *   &lt;property name="message" value="Hello World!"/&gt;
 * &lt;/bean&gt;
 *
 * &lt;bean id="groovyMessenger" class="org.springframework.scripting.bsh.GroovyScriptFactory"&gt;
 *   &lt;constructor-arg value="classpath:mypackage/Messenger.groovy"/&gt;
 *   &lt;property name="message" value="Hello World!"/&gt;
 * &lt;/bean&gt;</pre>
 *
 * <p><b>NOTE:</b> Please note that the above excerpt from a Spring
 * XML bean definition file uses just the &lt;bean/&gt;-style syntax
 * (in an effort to illustrate using the {@link ScriptFactoryPostProcessor} itself).
 * In reality, you would never create a &lt;bean/&gt; definition for a
 * {@link ScriptFactoryPostProcessor} explicitly; rather you would import the
 * tags from the <code>'lang'</code> namespace and simply create scripted
 * beans using the tags in that namespace... as part of doing so, a
 * {@link ScriptFactoryPostProcessor} will implicitly be created for you.
 *
 * <p>The Spring reference documentation contains numerous examples of using
 * tags in the <code>'lang'</code> namespace; by way of an example, find below
 * a Groovy-backed bean defined using the <code>'lang:groovy'</code> tag.
 *
 * <pre class="code">
 * &lt;?xml version="1.0" encoding="UTF-8"?&gt;
 * &lt;beans xmlns="http://www.springframework.org/schema/beans"
 *     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 *     xmlns:lang="http://www.springframework.org/schema/lang"&gt;
 *
 *   &lt;!-- this is the bean definition for the Groovy-backed Messenger implementation --&gt;
 *   &lt;lang:groovy id="messenger" script-source="classpath:Messenger.groovy"&gt;
 *     &lt;lang:property name="message" value="I Can Do The Frug" /&gt;
 *   &lt;/lang:groovy&gt;
 *
 *   &lt;!-- an otherwise normal bean that will be injected by the Groovy-backed Messenger --&gt;
 *   &lt;bean id="bookingService" class="x.y.DefaultBookingService"&gt;
 *     &lt;property name="messenger" ref="messenger" /&gt;
 *   &lt;/bean&gt;
 *
 * &lt;/beans&gt;</pre>
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rick Evans
 * @author Mark Fisher
 * @since 2.0
 */
public class ScriptFactoryPostProcessor extends InstantiationAwareBeanPostProcessorAdapter
		implements BeanClassLoaderAware, BeanFactoryAware, ResourceLoaderAware, DisposableBean, Ordered {

	/**
	 * The {@link org.springframework.core.io.Resource}-style prefix that denotes
	 * an inline script.
	 * <p>An inline script is a script that is defined right there in the (typically XML)
	 * configuration, as opposed to being defined in an external file.
	 */
	public static final String INLINE_SCRIPT_PREFIX = "inline:";

	public static final String REFRESH_CHECK_DELAY_ATTRIBUTE =
			Conventions.getQualifiedAttributeName(ScriptFactoryPostProcessor.class, "refreshCheckDelay");

	private static final String SCRIPT_FACTORY_NAME_PREFIX = "scriptFactory.";

	private static final String SCRIPTED_OBJECT_NAME_PREFIX = "scriptedObject.";


	/** Logger available to subclasses */
	protected final Log logger = LogFactory.getLog(getClass());

	private long defaultRefreshCheckDelay = -1;

	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

	private ConfigurableBeanFactory beanFactory;

	private ResourceLoader resourceLoader = new DefaultResourceLoader();

	final DefaultListableBeanFactory scriptBeanFactory = new DefaultListableBeanFactory();

	/** Map from bean name String to ScriptSource object */
	private final Map<String, ScriptSource> scriptSourceCache = new HashMap<String, ScriptSource>();


	/**
	 * Set the delay between refresh checks, in milliseconds.
	 * Default is -1, indicating no refresh checks at all.
	 * <p>Note that an actual refresh will only happen when
	 * the {@link org.springframework.scripting.ScriptSource} indicates
	 * that it has been modified.
	 * @see org.springframework.scripting.ScriptSource#isModified()
	 */
	public void setDefaultRefreshCheckDelay(long defaultRefreshCheckDelay) {
		this.defaultRefreshCheckDelay = defaultRefreshCheckDelay;
	}

	public void setBeanClassLoader(ClassLoader classLoader) {
		this.beanClassLoader = classLoader;
	}

	public void setBeanFactory(BeanFactory beanFactory) {
		if (!(beanFactory instanceof ConfigurableBeanFactory)) {
			throw new IllegalStateException("ScriptFactoryPostProcessor doesn't work with a BeanFactory " +
					"which does not implement ConfigurableBeanFactory: " + beanFactory.getClass());
		}
		this.beanFactory = (ConfigurableBeanFactory) beanFactory;

		// Required so that references (up container hierarchies) are correctly resolved.
		this.scriptBeanFactory.setParentBeanFactory(this.beanFactory);

		// Required so that all BeanPostProcessors, Scopes, etc become available.
		this.scriptBeanFactory.copyConfigurationFrom(this.beanFactory);

		// Filter out BeanPostProcessors that are part of the AOP infrastructure,
		// since those are only meant to apply to beans defined in the original factory.
		for (Iterator<BeanPostProcessor> it = this.scriptBeanFactory.getBeanPostProcessors().iterator(); it.hasNext();) {
			if (it.next() instanceof AopInfrastructureBean) {
				it.remove();
			}
		}
	}

	public void setResourceLoader(ResourceLoader resourceLoader) {
		this.resourceLoader = resourceLoader;
	}

	public int getOrder() {
		return Integer.MIN_VALUE;
	}


	@Override
	public Class predictBeanType(Class beanClass, String beanName) {
		// We only apply special treatment to ScriptFactory implementations here.
		if (!ScriptFactory.class.isAssignableFrom(beanClass)) {
			return null;
		}

		BeanDefinition bd = this.beanFactory.getMergedBeanDefinition(beanName);

		try {
			String scriptFactoryBeanName = SCRIPT_FACTORY_NAME_PREFIX + beanName;
			String scriptedObjectBeanName = SCRIPTED_OBJECT_NAME_PREFIX + beanName;
			prepareScriptBeans(bd, scriptFactoryBeanName, scriptedObjectBeanName);

			ScriptFactory scriptFactory = this.scriptBeanFactory.getBean(scriptFactoryBeanName, ScriptFactory.class);
			ScriptSource scriptSource =
					getScriptSource(scriptFactoryBeanName, scriptFactory.getScriptSourceLocator());
			Class[] interfaces = scriptFactory.getScriptInterfaces();

			Class scriptedType = scriptFactory.getScriptedObjectType(scriptSource);
			if (scriptedType != null) {
				return scriptedType;
			}
			else if (!ObjectUtils.isEmpty(interfaces)) {
				return (interfaces.length == 1 ? interfaces[0] : createCompositeInterface(interfaces));
			}
			else {
				if (bd.isSingleton()) {
					Object bean = this.scriptBeanFactory.getBean(scriptedObjectBeanName);
					if (bean != null) {
						return bean.getClass();
					}
				}
			}
		}
		catch (Exception ex) {
			if (ex instanceof BeanCreationException &&
					((BeanCreationException) ex).getMostSpecificCause() instanceof BeanCurrentlyInCreationException) {
				if (logger.isTraceEnabled()) {
					logger.trace("Could not determine scripted object type for bean '" + beanName + "': " + ex.getMessage());
				}
			}
			else {
				if (logger.isDebugEnabled()) {
					logger.debug("Could not determine scripted object type for bean '" + beanName + "'", ex);
				}
			}
		}

		return null;
	}

	@Override
	public Object postProcessBeforeInstantiation(Class beanClass, String beanName) {
		// We only apply special treatment to ScriptFactory implementations here.
		if (!ScriptFactory.class.isAssignableFrom(beanClass)) {
			return null;
		}

		BeanDefinition bd = this.beanFactory.getMergedBeanDefinition(beanName);
		String scriptFactoryBeanName = SCRIPT_FACTORY_NAME_PREFIX + beanName;
		String scriptedObjectBeanName = SCRIPTED_OBJECT_NAME_PREFIX + beanName;
		prepareScriptBeans(bd, scriptFactoryBeanName, scriptedObjectBeanName);

		ScriptFactory scriptFactory = this.scriptBeanFactory.getBean(scriptFactoryBeanName, ScriptFactory.class);
		ScriptSource scriptSource =
				getScriptSource(scriptFactoryBeanName, scriptFactory.getScriptSourceLocator());
		boolean isFactoryBean = false;
		try {
			Class scriptedObjectType = scriptFactory.getScriptedObjectType(scriptSource);
			// Returned type may be null if the factory is unable to determine the type.
			if (scriptedObjectType != null) {
				isFactoryBean = FactoryBean.class.isAssignableFrom(scriptedObjectType);
			}
		}
		catch (Exception ex) {
			throw new BeanCreationException(
					beanName, "Could not determine scripted object type for " + scriptFactory, ex);
		}

		long refreshCheckDelay = resolveRefreshCheckDelay(bd);
		if (refreshCheckDelay >= 0) {
			Class[] interfaces = scriptFactory.getScriptInterfaces();
			RefreshableScriptTargetSource ts = new RefreshableScriptTargetSource(
					this.scriptBeanFactory, scriptedObjectBeanName, scriptFactory, scriptSource, isFactoryBean);
			ts.setRefreshCheckDelay(refreshCheckDelay);
			return createRefreshableProxy(ts, interfaces);
		}

		if (isFactoryBean) {
			scriptedObjectBeanName = BeanFactory.FACTORY_BEAN_PREFIX + scriptedObjectBeanName;
		}
		return this.scriptBeanFactory.getBean(scriptedObjectBeanName);
	}


	/**
	 * Prepare the script beans in the internal BeanFactory that this
	 * post-processor uses. Each original bean definition will be split
	 * into a ScriptFactory definition and a scripted object definition.
	 * @param bd the original bean definition in the main BeanFactory
	 * @param scriptFactoryBeanName the name of the internal ScriptFactory bean
	 * @param scriptedObjectBeanName the name of the internal scripted object bean
	 */
	protected void prepareScriptBeans(
			BeanDefinition bd, String scriptFactoryBeanName, String scriptedObjectBeanName) {

		// Avoid recreation of the script bean definition in case of a prototype.
		synchronized (this.scriptBeanFactory) {
			if (!this.scriptBeanFactory.containsBeanDefinition(scriptedObjectBeanName)) {

				this.scriptBeanFactory.registerBeanDefinition(
						scriptFactoryBeanName, createScriptFactoryBeanDefinition(bd));
				ScriptFactory scriptFactory = this.scriptBeanFactory.getBean(scriptFactoryBeanName, ScriptFactory.class);
				ScriptSource scriptSource =
						getScriptSource(scriptFactoryBeanName, scriptFactory.getScriptSourceLocator());
				Class[] interfaces = scriptFactory.getScriptInterfaces();

				Class[] scriptedInterfaces = interfaces;
				if (scriptFactory.requiresConfigInterface() && !bd.getPropertyValues().isEmpty()) {
					Class configInterface = createConfigInterface(bd, interfaces);
					scriptedInterfaces = (Class[]) ObjectUtils.addObjectToArray(interfaces, configInterface);
				}

				BeanDefinition objectBd = createScriptedObjectBeanDefinition(
						bd, scriptFactoryBeanName, scriptSource, scriptedInterfaces);
				long refreshCheckDelay = resolveRefreshCheckDelay(bd);
				if (refreshCheckDelay >= 0) {
					objectBd.setScope(BeanDefinition.SCOPE_PROTOTYPE);
				}

				this.scriptBeanFactory.registerBeanDefinition(scriptedObjectBeanName, objectBd);
			}
		}
	}

	/**
	 * Get the refresh check delay for the given {@link ScriptFactory} {@link BeanDefinition}.
	 * If the {@link BeanDefinition} has a
	 * {@link org.springframework.core.AttributeAccessor metadata attribute}
	 * under the key {@link #REFRESH_CHECK_DELAY_ATTRIBUTE} which is a valid {@link Number}
	 * type, then this value is used. Otherwise, the the {@link #defaultRefreshCheckDelay}
	 * value is used.
	 * @param beanDefinition the BeanDefinition to check
	 * @return the refresh check delay
	 */
	protected long resolveRefreshCheckDelay(BeanDefinition beanDefinition) {
		long refreshCheckDelay = this.defaultRefreshCheckDelay;
		Object attributeValue = beanDefinition.getAttribute(REFRESH_CHECK_DELAY_ATTRIBUTE);
		if (attributeValue instanceof Number) {
			refreshCheckDelay = ((Number) attributeValue).longValue();
		}
		else if (attributeValue instanceof String) {
			refreshCheckDelay = Long.parseLong((String) attributeValue);
		}
		else if (attributeValue != null) {
			throw new BeanDefinitionStoreException(
					"Invalid refresh check delay attribute [" + REFRESH_CHECK_DELAY_ATTRIBUTE +
					"] with value [" + attributeValue + "]: needs to be of type Number or String");
		}
		return refreshCheckDelay;
	}

	/**
	 * Create a ScriptFactory bean definition based on the given script definition,
	 * extracting only the definition data that is relevant for the ScriptFactory
	 * (that is, only bean class and constructor arguments).
	 * @param bd the full script bean definition
	 * @return the extracted ScriptFactory bean definition
	 * @see org.springframework.scripting.ScriptFactory
	 */
	protected BeanDefinition createScriptFactoryBeanDefinition(BeanDefinition bd) {
		GenericBeanDefinition scriptBd = new GenericBeanDefinition();
		scriptBd.setBeanClassName(bd.getBeanClassName());
		scriptBd.getConstructorArgumentValues().addArgumentValues(bd.getConstructorArgumentValues());
		return scriptBd;
	}

	/**
	 * Obtain a ScriptSource for the given bean, lazily creating it
	 * if not cached already.
	 * @param beanName the name of the scripted bean
	 * @param scriptSourceLocator the script source locator associated with the bean
	 * @return the corresponding ScriptSource instance
	 * @see #convertToScriptSource
	 */
	protected ScriptSource getScriptSource(String beanName, String scriptSourceLocator) {
		synchronized (this.scriptSourceCache) {
			ScriptSource scriptSource = this.scriptSourceCache.get(beanName);
			if (scriptSource == null) {
				scriptSource = convertToScriptSource(beanName, scriptSourceLocator, this.resourceLoader);
				this.scriptSourceCache.put(beanName, scriptSource);
			}
			return scriptSource;
		}
	}

	/**
	 * Convert the given script source locator to a ScriptSource instance.
	 * <p>By default, supported locators are Spring resource locations
	 * (such as "file:C:/myScript.bsh" or "classpath:myPackage/myScript.bsh")
	 * and inline scripts ("inline:myScriptText...").
	 * @param beanName the name of the scripted bean
	 * @param scriptSourceLocator the script source locator
	 * @param resourceLoader the ResourceLoader to use (if necessary)
	 * @return the ScriptSource instance
	 */
	protected ScriptSource convertToScriptSource(
			String beanName, String scriptSourceLocator, ResourceLoader resourceLoader) {

		if (scriptSourceLocator.startsWith(INLINE_SCRIPT_PREFIX)) {
			return new StaticScriptSource(scriptSourceLocator.substring(INLINE_SCRIPT_PREFIX.length()), beanName);
		}
		else {
			return new ResourceScriptSource(resourceLoader.getResource(scriptSourceLocator));
		}
	}

	/**
	 * Create a config interface for the given bean definition, defining setter
	 * methods for the defined property values as well as an init method and
	 * a destroy method (if defined).
	 * <p>This implementation creates the interface via CGLIB's InterfaceMaker,
	 * determining the property types from the given interfaces (as far as possible).
	 * @param bd the bean definition (property values etc) to create a
	 * config interface for
	 * @param interfaces the interfaces to check against (might define
	 * getters corresponding to the setters we're supposed to generate)
	 * @return the config interface
	 * @see net.sf.cglib.proxy.InterfaceMaker
	 * @see org.springframework.beans.BeanUtils#findPropertyType
	 */
	protected Class createConfigInterface(BeanDefinition bd, Class[] interfaces) {
		InterfaceMaker maker = new InterfaceMaker();
		PropertyValue[] pvs = bd.getPropertyValues().getPropertyValues();
		for (PropertyValue pv : pvs) {
			String propertyName = pv.getName();
			Class propertyType = BeanUtils.findPropertyType(propertyName, interfaces);
			String setterName = "set" + StringUtils.capitalize(propertyName);
			Signature signature = new Signature(setterName, Type.VOID_TYPE, new Type[] {Type.getType(propertyType)});
			maker.add(signature, new Type[0]);
		}
		if (bd instanceof AbstractBeanDefinition) {
			AbstractBeanDefinition abd = (AbstractBeanDefinition) bd;
			if (abd.getInitMethodName() != null) {
				Signature signature = new Signature(abd.getInitMethodName(), Type.VOID_TYPE, new Type[0]);
				maker.add(signature, new Type[0]);
			}
			if (abd.getDestroyMethodName() != null) {
				Signature signature = new Signature(abd.getDestroyMethodName(), Type.VOID_TYPE, new Type[0]);
				maker.add(signature, new Type[0]);
			}
		}
		return maker.create();
	}

	/**
	 * Create a composite interface Class for the given interfaces,
	 * implementing the given interfaces in one single Class.
	 * <p>The default implementation builds a JDK proxy class
	 * for the given interfaces.
	 * @param interfaces the interfaces to merge
	 * @return the merged interface as Class
	 * @see java.lang.reflect.Proxy#getProxyClass
	 */
	protected Class createCompositeInterface(Class[] interfaces) {
		return ClassUtils.createCompositeInterface(interfaces, this.beanClassLoader);
	}

	/**
	 * Create a bean definition for the scripted object, based on the given script
	 * definition, extracting the definition data that is relevant for the scripted
	 * object (that is, everything but bean class and constructor arguments).
	 * @param bd the full script bean definition
	 * @param scriptFactoryBeanName the name of the internal ScriptFactory bean
	 * @param scriptSource the ScriptSource for the scripted bean
	 * @param interfaces the interfaces that the scripted bean is supposed to implement
	 * @return the extracted ScriptFactory bean definition
	 * @see org.springframework.scripting.ScriptFactory#getScriptedObject
	 */
	protected BeanDefinition createScriptedObjectBeanDefinition(
			BeanDefinition bd, String scriptFactoryBeanName, ScriptSource scriptSource, Class[] interfaces) {

		GenericBeanDefinition objectBd = new GenericBeanDefinition(bd);
		objectBd.setFactoryBeanName(scriptFactoryBeanName);
		objectBd.setFactoryMethodName("getScriptedObject");
		objectBd.getConstructorArgumentValues().clear();
		objectBd.getConstructorArgumentValues().addIndexedArgumentValue(0, scriptSource);
		objectBd.getConstructorArgumentValues().addIndexedArgumentValue(1, interfaces);
		return objectBd;
	}

	/**
	 * Create a refreshable proxy for the given AOP TargetSource.
	 * @param ts the refreshable TargetSource
	 * @param interfaces the proxy interfaces (may be <code>null</code> to
	 * indicate proxying of all interfaces implemented by the target class)
	 * @return the generated proxy
	 * @see RefreshableScriptTargetSource
	 */
	protected Object createRefreshableProxy(TargetSource ts, Class[] interfaces) {
		ProxyFactory proxyFactory = new ProxyFactory();
		proxyFactory.setTargetSource(ts);

		if (interfaces == null) {
			interfaces = ClassUtils.getAllInterfacesForClass(ts.getTargetClass(), this.beanClassLoader);
		}
		proxyFactory.setInterfaces(interfaces);

		DelegatingIntroductionInterceptor introduction = new DelegatingIntroductionInterceptor(ts);
		introduction.suppressInterface(TargetSource.class);
		proxyFactory.addAdvice(introduction);

		return proxyFactory.getProxy(this.beanClassLoader);
	}


	/**
	 * Destroy the inner bean factory (used for scripts) on shutdown.
	 */
	public void destroy() {
		this.scriptBeanFactory.destroySingletons();
	}

}