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();

    }
}

 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