Spring AOP代理

Spring AOP代理

到目前为止,我们学习过如何使用<aop:config><aop:aspectj-autoproxy>声明方面。也可以通过编程方式创建代理,并使用代理对象以编程方式调用方面。

语法

//Create object to be proxied
Student student = new Student();
//Create the Proxy Factory
AspectJProxyFactory proxyFactory = new AspectJProxyFactory(student);
//Add Aspect class to the factory
proxyFactory.addAspect(Logging.class);
//Get the proxy object
Student proxyStudent = proxyFactory.getProxy();
//Invoke the proxied method.
proxyStudent.getAge();

在上面的语法示例中 -

  • AspectJProxyFactory - 用于创建代理对象的工厂类。
  • Logging.class - 包含通知的方面类
  • Student - 将被通知的业务类。

要了解上面提到与代理相关的概念,我们写一个Spring AOP基于注解的应用例子,它将使用基于注解配置实现通知。打开并使用Eclipse IDE,并按照以下步骤创建一个Spring应用程序:

  1. 更新在Spring AOP应用实例中创建过的Student项目。
  2. 更新bean配置并运行应用程序,如下所述。

整个项目的目录结构如下所示 -

下面是Logging.java文件的内容。 这实际上是一个Aspect模块的样本,它定义了在各个点被调用的方法。

package com.zyiz;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.annotation.Before;

@Aspect
public class Logging {

   /** Following is the definition for a pointcut to select
    *  all the methods available. So advice will be called
    *  for all the methods.
    */
   @Pointcut("execution(* com.zyiz.Student.getAge(..))")
   private void selectGetAge(){}

   /** 
    * This is the method which I would like to execute
    * before a selected method execution.
    */
   @Before("selectGetAge()")
   public void beforeAdvice(){
      System.out.println("[beforeAdvice] Going to setup student profile.");
   }  
}

以下是Student.java文件的内容:

package com.zyiz;

public class Student {
   private Integer age;

   public void setAge(Integer age) {
      this.age = age;
   }
   public Integer getAge() {
      System.out.println("Age : " + age );
      return age;
   }   
}

以下是MainApp.java文件的内容:

package com.zyiz;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.aop.aspectj.annotation.AspectJProxyFactory;

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = 
             new ClassPathXmlApplicationContext("Beans.xml");

      Student student = (Student) context.getBean("student");

      //Create the Proxy Factory
      AspectJProxyFactory proxyFactory = new AspectJProxyFactory(student);

      //Add Aspect class to the factory
      proxyFactory.addAspect(Logging.class);

      //Get the proxy object
      Student proxyStudent = proxyFactory.getProxy();

      //Invoke the proxied method.
      proxyStudent.getAge();

   }
}

以下是配置文件Beans.xml文件的内容:

<?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-3.0.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-3.0.xsd ">

   <!-- Definition for student bean -->
   <bean id="student" class="com.zyiz.Student">
      <property name="age"  value="26"/>      
   </bean>

   <!-- Definition for logging aspect -->
   <bean id="logging" class="com.zyiz.Logging"/> 

</beans>

运行项目

完成创建源代码和配置文件后,运行应用程序。右键单击应用程序中的MainApp.java,并使用运行方式作为Java应用程序命令。 如果您的应用程序一切正常,这将打印以下消息:

[beforeAdvice] Going to setup student profile.
Age : 26