Spring AOP 入门实例

AOP 面向切面，可以让我们在不修改业务代码的前提下，在业务代码执行前后进行执行相应的模块，这样，我们就可以把诸如日志的功能模块合核心业务模块分隔开来，以往的的日志做法都是由核心模块主动的调用日志记录功能，耦合性很强，使用AOP技术，可以将日志模块作为切面，插入到核心业务前执行，核心业务并不主动的调用日志记录功能

本例中使用GreetingHelloworldImpl代表核心业务模块，使用LoggerService代表作为aop实现的日志模块

核心业务并没有主动依赖日志模块


package SimpleAOPTest;






public interface GreetingHelloworld ......{


public void sayHelloworld();


}






package SimpleAOPTest;






public class GreetingHelloworldImpl implements GreetingHelloworld ......{


private String greetingText;


private String greetingFromConstructor;




public GreetingHelloworldImpl(String greetingFromConstructor)......{


this.greetingFromConstructor=greetingFromConstructor;


}




public GreetingHelloworldImpl()......{




}




public String getGreetingText() ......{


return greetingText;


}




public void setGreetingText(String greetingText) ......{


this.greetingText = greetingText;


}




public void sayHelloworld() ......{


System.out.println(this.getGreetingText());


System.out.println(this.getGreetingFromConstructor());


}




public String getGreetingFromConstructor() ......{


return greetingFromConstructor;


}




public void setGreetingFromConstructor(String greetingFromConstructor) ......{


this.greetingFromConstructor = greetingFromConstructor;


}




}



日志模块：


package SimpleAOPTest;




import java.lang.reflect.Method;




import org.springframework.aop.MethodBeforeAdvice;






public class LoggerService implements MethodBeforeAdvice ......{




public LoggerService()......{




}


public void before(Method method, Object[] obj, Object target)




throws Throwable ......{


System.out.println("this is info from LoggerService");


}




}



配置文件：


<?xml version="1.0" encoding="UTF-8"?>


<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >


<beans>


<bean id="greetingTarget" class="SimpleAOPTest.GreetingHelloworldImpl">


<constructor-arg>


<value>this is helloworld from construtor</value>


</constructor-arg>


<property name="greetingText">


<value>hello world!</value>


</property>


</bean>




<bean id="loggerService" class="SimpleAOPTest.LoggerService"></bean>


<bean id="greeting" class="org.springframework.aop.framework.ProxyFactoryBean">


<property name="proxyInterfaces">


<list>


<value>SimpleAOPTest.GreetingHelloworld</value> <!-- 拦截GreetingHelloworld接口中的方法 -->


</list>


</property>


<property name="interceptorNames">


<list>


<value>loggerService</value> <!-- 处理loggerService请求，切入 -->


</list>


</property>


<property name="target">


<ref bean="greetingTarget"/> <!-- 然后处理greeting请求 -->


</property>


<!-- 代理目标为类时设置


<property name="proxyTargetClass">


<value>true</value>


</property>


-->


</bean>


</beans>



测试代码：


package SimpleAOPTest;




import java.io.File;




import org.springframework.beans.factory.BeanFactory;


import org.springframework.beans.factory.xml.XmlBeanFactory;


import org.springframework.core.io.FileSystemResource;






public class TestHelloWorld ......{






public static void main(String[] args) ......{




String filePath=System.getProperty("user.dir")+File.separator+"SimpleAOPTest"+File.separator+"hello.xml";




BeanFactory factory=new XmlBeanFactory(new FileSystemResource(filePath));


//代理目标为接口时使用


GreetingHelloworld greetingSerview=(GreetingHelloworld)factory.getBean("greeting");


//代理目标为类是使用，并配置xml中proxyTargetClass，需要CGLIB包


//<property name="proxyTargetClass">


//<value>true</value>


//</property>


//GreetingHelloworldImpl greetingSerview=(GreetingHelloworldImpl)factory.getBean("greeting");


greetingSerview.sayHelloworld();




}




// public static String getRealPath(String filename){


// String path="";


// Class theClass=TestHelloWorld.class;


// java.net.URL u= theClass.getResource(filename);


// return u.getPath();


//


//


// }


}



运行结果：
2007-5-14 23:13:47 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from file [E:/项目/SpringInActionStudy/SimpleAOPTest/hello.xml]
this is info from LoggerService
hello world!
this is helloworld from construtor
可以看到，日志模块打印的信息“this is info from LoggerService”在核心业务运行之前执行了，这样，我们就算对日至模块进行天翻地覆的变化，都不会影响我们的核心业务