Spring AOP-基于建议的注释

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📜 Spring AOP-基于建议的注释

📅 最后修改于: 2020-11-11 05:23:50 🧑 作者: Mango

@Around是建议类型，可确保建议可以在方法执行之前和之后运行。以下是@Around建议的语法。

句法

@PointCut("execution(* com.tutorialspoint.Student.getAge(..))")
private void selectGetName(){}

@Around("selectGetAge()")
public void aroundAdvice(ProceedingJoinPoint proceedingJoinPoint){
   System.out.println("Around advice");
   Object[] args = jp.getArgs();
   if(args.length>0){
      System.out.print("Arguments passed: " );
      for (int i = 0; i < args.length; i++) {
         System.out.print("arg "+(i+1)+": "+args[i]);
      }
   }

   Object result = jp.proceed(args);
   System.out.println("Returning " + result);
   return result.toString();   
}

哪里，

@ PointCut-将函数标记为PointCut
execution(expression) -涵盖将要应用建议的方法的表达式。
@Around-将函数标记为要在PointCut涵盖的方法之前执行的建议。

为了理解与@Around Advice相关的上述概念，让我们编写一个实现@Around Advice的示例。为了在没有任何建议的情况下编写示例，请让我们准备好运行的Eclipse IDE，并使用以下步骤创建Spring应用程序-

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Aspect模块的示例，它定义了要在各个点调用的方法。

package com.tutorialspoint;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.PointCut;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.ProceedingJoinPoint; 

@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
    * around a selected method execution.
    */
   @Around("selectGetAge()")
   public void aroundAdvice(ProceedingJoinPoint proceedingJoinPoint) throws Throwable{
      System.out.println("Around advice");
      Object[] args = proceedingJoinPoint.getArgs();
      if(args.length>0){
         System.out.print("Arguments passed: " );
         for (int i = 0; i < args.length; i++) {
            System.out.print("arg "+(i+1)+": "+args[i]);
         }
      }

      Object result = proceedingJoinPoint.proceed(args);
      System.out.println("Returning " + result);
   }  
}

以下是Student.java文件的内容。

package com.tutorialspoint;

public class Student {
   private Integer age;
   private String name;

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

   public void setName(String name) {
      this.name = name;
   }
   
   public String getName() {
      System.out.println("Name : " + name );
      return name;
   }
   
   public void printThrowException(){
      System.out.println("Exception raised");
      throw new IllegalArgumentException();
   }
}

以下是MainApp.java文件的内容。

package com.tutorialspoint;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

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

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

      student.getAge();     
   }
}

以下是配置文件Beans.xml 。

运行项目

完成创建源文件和配置文件后，运行您的应用程序。右键单击应用程序中的MainApp.java，然后使用“以Java应用程序身份运行”命令。如果您的应用程序一切正常，它将打印以下消息。

Around advice
Age : 11
Returning 11