/*
 * Copyright 2002-2018 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
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 * 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
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package org.springframework.beans.factory.config;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.FactoryBeanNotInitializedException;
import org.springframework.lang.Nullable;

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.

Note that as it is expected to be used mostly for accessing factory methods, this factory by default operates in a singleton fashion. The first request to getObject by the owning bean factory will cause a method invocation, whose return value will be cached for subsequent requests. An internal singleton property may be set to "false", to cause this factory to invoke the target method each time it is asked for an object.

NOTE: If your target method does not produce a result to expose, consider MethodInvokingBean instead, which avoids the type determination and lifecycle limitations that this MethodInvokingFactoryBean comes with.

This invoker supports any kind of target method. A static method may be specified by setting the targetMethod property to a String representing the static method name, with targetClass specifying the Class that the static method is defined on. Alternatively, a target instance method may be specified, by setting the targetObject property as the target object, and the 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 arguments property.

This class depends on afterPropertiesSet() being called once all properties have been set, as per the InitializingBean contract.

An example (in an XML based bean factory definition) of a bean definition which uses this class to call a static factory method:

<bean id="myObject" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
  <property name="staticMethod" value="com.whatever.MyClassFactory.getInstance"/>
</bean>

An example of calling a static method then an instance method to get at a Java system property. Somewhat verbose, but it works.

<bean id="sysProps" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
  <property name="targetClass" value="java.lang.System"/>
  <property name="targetMethod" value="getProperties"/>
</bean>
<bean id="javaVersion" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
  <property name="targetObject" ref="sysProps"/>
  <property name="targetMethod" value="getProperty"/>
  <property name="arguments" value="java.version"/>
</bean>
Author:Colin Sampaleanu, Juergen Hoeller
See Also:
Since:21.11.2003
/** * {@link 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><b>NOTE: If your target method does not produce a result to expose, consider * {@link MethodInvokingBean} instead, which avoids the type determination and * lifecycle limitations that this {@link MethodInvokingFactoryBean} comes with.</b> * * <p>This invoker supports any kind of target method. A static 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"> * &lt;bean id="myObject" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> * &lt;property name="staticMethod" value="com.whatever.MyClassFactory.getInstance"/> * &lt;/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"> * &lt;bean id="sysProps" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> * &lt;property name="targetClass" value="java.lang.System"/> * &lt;property name="targetMethod" value="getProperties"/> * &lt;/bean> * * &lt;bean id="javaVersion" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> * &lt;property name="targetObject" ref="sysProps"/> * &lt;property name="targetMethod" value="getProperty"/> * &lt;property name="arguments" value="java.version"/> * &lt;/bean></pre> * * @author Colin Sampaleanu * @author Juergen Hoeller * @since 21.11.2003 * @see MethodInvokingBean * @see org.springframework.util.MethodInvoker */
public class MethodInvokingFactoryBean extends MethodInvokingBean implements FactoryBean<Object> { private boolean singleton = true; private boolean initialized = false;
Method call result in the singleton case.
/** Method call result in the singleton case. */
@Nullable private Object singletonObject;
Set if a singleton should be created, or a new object on each getObject() request otherwise. Default is "true".
/** * Set if a singleton should be created, or a new object on each * {@link #getObject()} request otherwise. Default is "true". */
public void setSingleton(boolean singleton) { this.singleton = singleton; } @Override public void afterPropertiesSet() throws Exception { prepare(); if (this.singleton) { this.initialized = true; this.singletonObject = invokeWithTargetException(); } }
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.
/** * 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. */
@Override @Nullable 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 invokeWithTargetException(); } }
Return the type of object that this FactoryBean creates, or null if not known in advance.
/** * Return the type of object that this FactoryBean creates, * or {@code null} if not known in advance. */
@Override public Class<?> getObjectType() { if (!isPrepared()) { // Not fully initialized yet -> return null to indicate "not known yet". return null; } return getPreparedMethod().getReturnType(); } @Override public boolean isSingleton() { return this.singleton; } }