/*
* 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</b> 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</code> 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();
}
}