Springaop 简明教程

Spring AOP - Proxy

到目前为止，我们已经使用 <aop:config> 或 < aop:aspectj-autoproxy> 声明了方面。我们可以以编程方式创建代理，也可以使用代理对象以编程方式调用方面。

So far, we’ve declared aspects using <aop:config> or < aop:aspectj-autoproxy>. We can create a proxy programmatically as well as invoke the aspects programmatically using the proxy object.

Syntax

//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();

其中，

Where,

  1. AspectJProxyFactory − Factory class to create a proxy object.

  2. Logging.class − Class of the Aspect containing advices.

  3. Student − Business class to be advised.

为了理解与代理相关的上述概念，我们来写一个将实施代理的示例。若要使用少量的建议来编写示例，我们先来设置一个可行的 Eclipse IDE，然后使用以下步骤来创建一个 Spring 应用程序：

To understand the above-mentioned concepts related to proxy, let us write an example which will implement proxy. To write our example with few advices, let us have a working Eclipse IDE in place and use the following steps to create a Spring application −

Step

Description

1

Update the project Student created under chapter Spring AOP - Application.

2

Update the bean configuration and run the application as explained below.

以下是 Logging.java 文件的内容。这实际上是方面模块的一个示例，它定义了在各个点调用的方法。

Following is the content of Logging.java file. This is actually a sample of aspect module, which defines the methods to be called at various points.

package com.tutorialspoint;

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.tutorialspoint.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("Going to setup student profile.");
   }
}

以下是 Student.java 文件的内容。

Following is the content of the Student.java file.

package com.tutorialspoint;

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。

Following is the content of the MainApp.java file.

package com.tutorialspoint;

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 。

Following is the configuration file Beans.xml.

<?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.tutorialspoint.Student">
      <property name = "age"  value = "11"/>
   </bean>

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

Run Project

创建源和配置文件后，运行您的应用程序。在应用程序中右键单击 MainApp.java 并使用 run as Java Application 命令。如果您的应用程序一切正常，它将打印以下消息。

Once you are done creating the source and configuration files, run your application. Rightclick on MainApp.java in your application and use run as Java Application command. If everything is fine with your application, it will print the following message.

Going to setup student profile.
Age : 11