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Spring Framework example source code file (MethodInvokingFactoryBean.java)

This example Spring Framework source code file (MethodInvokingFactoryBean.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Spring Framework tags/keywords

argumentconvertingmethodinvoker, class, classloader, configurablebeanfactory, configurablebeanfactory, error, error, exception, exception, factorybean, initializingbean, methodinvokingfactorybean, object, object, reflection

The Spring Framework MethodInvokingFactoryBean.java source code

/*
 * Copyright 2002-2007 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.beans.factory.config;

import java.lang.reflect.InvocationTargetException;

import org.springframework.beans.TypeConverter;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.FactoryBeanNotInitializedException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.support.ArgumentConvertingMethodInvoker;
import org.springframework.util.ClassUtils;

/**
 * FactoryBean which returns a value which is the result of a static or instance
 * method invocation. For most use cases it is better to just use the container's 
 * built-in factory method support for the same purpose, since that is smarter at
 * converting arguments. This factory bean is still useful though when you need to
 * call a method which doesn't return any value (for example, a static class method
 * to force some sort of initialization to happen). This use case is not supported
 * by factory methods, since a return value is needed to obtain the bean instance.
 *
 * <p>Note that as it is expected to be used mostly for accessing factory methods,
 * this factory by default operates in a <b>singleton fashion. The first request
 * to {@link #getObject} by the owning bean factory will cause a method invocation,
 * whose return value will be cached for subsequent requests. An internal
 * {@link #setSingleton singleton} property may be set to "false", to cause this
 * factory to invoke the target method each time it is asked for an object.
 *
 * <p>A static target method may be specified by setting the
 * {@link #setTargetMethod targetMethod} property to a String representing the static
 * method name, with {@link #setTargetClass targetClass} specifying the Class that
 * the static method is defined on. Alternatively, a target instance method may be
 * specified, by setting the {@link #setTargetObject targetObject} property as the target
 * object, and the {@link #setTargetMethod targetMethod} property as the name of the
 * method to call on that target object. Arguments for the method invocation may be
 * specified by setting the {@link #setArguments arguments} property.
 *
 * <p>This class depends on {@link #afterPropertiesSet()} being called once
 * all properties have been set, as per the InitializingBean contract.
 * 
 * <p>An example (in an XML based bean factory definition) of a bean definition
 * which uses this class to call a static factory method:
 *
 * <pre class="code">
 * <bean id="myObject" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
 *   <property name="staticMethod"><value>com.whatever.MyClassFactory.getInstance</value></property>
 * </bean></pre>
 *
 * <p>An example of calling a static method then an instance method to get at a
 * Java system property. Somewhat verbose, but it works.
 *
 * <pre class="code">
 * <bean id="sysProps" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
 *   <property name="targetClass"><value>java.lang.System</value></property>
 *   <property name="targetMethod"><value>getProperties</value></property>
 * </bean>
 *
 * <bean id="javaVersion" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
 *   <property name="targetObject"><ref local="sysProps"/></property>
 *   <property name="targetMethod"><value>getProperty</value></property>
 *   <property name="arguments">
 *     <list>
 *       <value>java.version</value>
 *     </list>
 *   </property>
 * </bean></pre>
 * 
 * @author Colin Sampaleanu
 * @author Juergen Hoeller
 * @since 21.11.2003
 */
public class MethodInvokingFactoryBean extends ArgumentConvertingMethodInvoker
		implements FactoryBean, BeanClassLoaderAware, BeanFactoryAware, InitializingBean {

	private boolean singleton = true;

	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

	private ConfigurableBeanFactory beanFactory;

	private boolean initialized = false;

	/** Method call result in the singleton case */
	private Object singletonObject;


	/**
	 * Set if a singleton should be created, or a new object on each
	 * request else. Default is "true".
	 */
	public void setSingleton(boolean singleton) {
		this.singleton = singleton;
	}

	public boolean isSingleton() {
		return this.singleton;
	}

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

	protected Class resolveClassName(String className) throws ClassNotFoundException {
		return ClassUtils.forName(className, this.beanClassLoader);
	}

	public void setBeanFactory(BeanFactory beanFactory) {
		if (beanFactory instanceof ConfigurableBeanFactory) {
			this.beanFactory = (ConfigurableBeanFactory) beanFactory;
		}
	}

	/**
	 * Obtain the TypeConverter from the BeanFactory that this bean runs in,
	 * if possible.
	 * @see ConfigurableBeanFactory#getTypeConverter()
	 */
	protected TypeConverter getDefaultTypeConverter() {
		if (this.beanFactory != null) {
			return this.beanFactory.getTypeConverter();
		}
		else {
			return super.getDefaultTypeConverter();
		}
	}


	public void afterPropertiesSet() throws Exception {
		prepare();
		if (this.singleton) {
			this.initialized = true;
			this.singletonObject = doInvoke();
		}
	}

	/**
	 * Perform the invocation and convert InvocationTargetException
	 * into the underlying target exception.
	 */
	private Object doInvoke() throws Exception {
		try {
			return invoke();
		}
		catch (InvocationTargetException ex) {
			if (ex.getTargetException() instanceof Exception) {
				throw (Exception) ex.getTargetException();
			}
			if (ex.getTargetException() instanceof Error) {
				throw (Error) ex.getTargetException();
			}
			throw ex;
		}
	}


	/**
	 * Returns the same value each time if the singleton property is set
	 * to "true", otherwise returns the value returned from invoking the
	 * specified method on the fly.
	 */
	public Object getObject() throws Exception {
		if (this.singleton) {
			if (!this.initialized) {
				throw new FactoryBeanNotInitializedException();
			}
			// Singleton: return shared object.
			return this.singletonObject;
		}
		else {
			// Prototype: new object on each call.
			return doInvoke();
		}
	}

	/**
	 * Return the type of object that this FactoryBean creates,
	 * or <code>null if not known in advance.
	 */
	public Class getObjectType() {
		if (!isPrepared()) {
			// Not fully initialized yet -> return null to indicate "not known yet".
			return null;
		}
		return getPreparedMethod().getReturnType();
	}

}

Other Spring Framework examples (source code examples)

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