Spring实战之org.springframework.beans.factory.config.MethodInvokingFactoryBean

在用spring管理我们的类的时候有时候希望有些属性值是来源于一些配置文件，系统属性，或者一些方法调用的结果，对于前两种使用方式可以使用spring的PropertyPlaceholderConfigurer类来注入，这些内容已经在前面的文章中说过，这里就不在重复了。这里就针对第三种情况做一些说明，其实在spring中是提供了对这种需求的解决方案的，那就是使用org.springframework.beans.factory.config.MethodInvokingFactoryBean类来生成需要注入的bean的属性，下面是一个例子

MyBean.java一个普通的POJO类

importorg.apache.commons.lang.builder.ToStringBuilder;
publicclassMyBean{
privateStringname;
privateStringjavaVersion;

publicStringgetName(){
returnname;
}
publicvoidsetName(Stringname){
this.name=name;
}
publicStringgetJavaVersion(){
returnjavaVersion;
}
publicvoidsetJavaVersion(StringjavaVersion){
this.javaVersion=javaVersion;
}
@Override
publicStringtoString(){
returnToStringBuilder.reflectionToString(this);
}
}

import org.apache.commons.lang.builder.ToStringBuilder;
public class MyBean {
	private String name;
	private String javaVersion;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getJavaVersion() {
		return javaVersion;
	}
	public void setJavaVersion(String javaVersion) {
		this.javaVersion = javaVersion;
	}
	@Override
	public String toString() {
		return ToStringBuilder.reflectionToString(this);
	}
}

MyBeanNameProvider.java提供一个静态方法用来生成MyBean类的name属性，同理非静态方法也是可以的，参考本例子中javaVersion属性定义

publicclassMyBeanNameProvider{
publicstaticStringgetName(){
return""+System.currentTimeMillis();
}
}

public class MyBeanNameProvider {
	public static String getName() {
		return "" + System.currentTimeMillis();
	}
}

spring.xml

<?xmlversion="1.0"encoding="UTF-8"?>
<beansxmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-2.0.xsd"
default-lazy-init="true">
<beanid="myBean"class="MyBean">
<propertyname="name"><reflocal="myBeanName"/></property>
<propertyname="javaVersion"><reflocal="javaVersion"/></property>
</bean>
<beanid="sysProps"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<propertyname="targetClass">
<value>java.lang.System</value>
</property>
<propertyname="targetMethod">
<value>getProperties</value>
</property>
</bean>
<beanid="javaVersion"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<propertyname="targetObject">
<reflocal="sysProps"/>
</property>
<propertyname="targetMethod">
<value>getProperty</value>
</property>
<propertyname="arguments">
<list>
<value>java.version</value>
</list>
</property>
</bean>

<beanid="myBeanName"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
<propertyname="staticMethod"><value>MyBeanNameProvider.getName</value></property>
</bean>
</beans>

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
                           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd"
       default-lazy-init="true">
	<bean id="myBean" class="MyBean">
		<property name="name"><ref local="myBeanName"/></property>
		<property name="javaVersion"><ref local="javaVersion"/></property>
	</bean>
	<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>
	
	 <bean id="myBeanName" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
		<property name="staticMethod"><value>MyBeanNameProvider.getName</value></property>
	</bean>
</beans>

Test.java一个测试类

importorg.springframework.context.ApplicationContext;
importorg.springframework.context.support.ClassPathXmlApplicationContext;
publicclassTest{
publicstaticvoidmain(String[]args){
ApplicationContextctx=newClassPathXmlApplicationContext("spring.xml");
MyBeanmyBean=(MyBean)ctx.getBean("myBean");
System.out.println(myBean);
}
}

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
	public static void main(String[] args) {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");
		MyBean myBean = (MyBean) ctx.getBean("myBean");
		System.out.println(myBean);
	}
}

运行Test类，就可以看到MyBean的两个属性都通过spring配置的方式注入到了类中