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

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1. importorg.apache.commons.lang.builder.ToStringBuilder;
2. publicclassMyBean{
3. privateStringname;
4. privateStringjavaVersion;
6. publicStringgetName(){
7. returnname;
8. }
9. publicvoidsetName(Stringname){
10. this.name=name;
11. }
12. publicStringgetJavaVersion(){
13. returnjavaVersion;
14. }
15. publicvoidsetJavaVersion(StringjavaVersion){
16. this.javaVersion=javaVersion;
17. }
18. @Override
19. publicStringtoString(){
20. returnToStringBuilder.reflectionToString(this);
21. }
22. }

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

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1. publicclassMyBeanNameProvider{
2. publicstaticStringgetName(){
3. return""+System.currentTimeMillis();
4. }
5. }

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

spring.xml

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1. <?xmlversion="1.0"encoding="UTF-8"?>
2. <beansxmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.0.xsd
6. http://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-2.0.xsd"
7. default-lazy-init="true">
8. <beanid="myBean"class="MyBean">
9. <propertyname="name"><reflocal="myBeanName"/></property>
10. <propertyname="javaVersion"><reflocal="javaVersion"/></property>
11. </bean>
12. <beanid="sysProps"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
13. <propertyname="targetClass">
14. <value>java.lang.System</value>
15. </property>
16. <propertyname="targetMethod">
17. <value>getProperties</value>
18. </property>
19. </bean>
20. <beanid="javaVersion"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
21. <propertyname="targetObject">
22. <reflocal="sysProps"/>
23. </property>
24. <propertyname="targetMethod">
25. <value>getProperty</value>
26. </property>
27. <propertyname="arguments">
28. <list>
29. <value>java.version</value>
30. </list>
31. </property>
32. </bean>
34. <beanid="myBeanName"class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
35. <propertyname="staticMethod"><value>MyBeanNameProvider.getName</value></property>
36. </bean>
37. </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

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1. importorg.springframework.context.ApplicationContext;
2. importorg.springframework.context.support.ClassPathXmlApplicationContext;
3. publicclassTest{
4. publicstaticvoidmain(String[]args){
5. ApplicationContextctx=newClassPathXmlApplicationContext("spring.xml");
6. MyBeanmyBean=(MyBean)ctx.getBean("myBean");
7. System.out.println(myBean);
8. }
9. }

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