Spring AOP - 基于XML的后置通知

后置通知是一种确保通知在方法执行后运行的通知类型。以下是后置通知的语法。

语法

<aop:config>
   <aop:aspect id = "log" ref = "logging">
      <aop:pointcut id = "PointCut-id" expression = "execution( expression )"/>    
      <aop:after pointcut-ref = "PointCut-id" method = "methodName"/>
   </aop:aspect>
</aop:config>

其中，

• PointCut-id - 切点的ID。

• methodName - 在被调用函数之后要调用的函数的函数名。

为了理解上述与后置通知相关的概念，让我们编写一个实现后置通知的示例。为了编写包含少量通知的示例，让我们准备好一个可运行的Eclipse IDE，并使用以下步骤创建一个Spring应用程序。

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

package com.tutorialspoint;

public class Logging {
   /** 
      * This is the method which I would like to execute
      * after a selected method execution.
   */
   public void afterAdvice(){
      System.out.println("Student profile setup complete.");
   }   
}

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.getName();
      student.getAge();     
   }
}

以下是配置文件Beans.xml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 ">

   <aop:config>
      <aop:aspect id = "log" ref = "logging">
         <aop:pointcut id = "selectAll" 
            expression = "execution(* com.tutorialspoint.Student.getAge(..))"/>
         <aop:after pointcut-ref = "selectAll" method = "afterAdvice"/>
      </aop:aspect>
   </aop:config>

   <!-- Definition for student bean -->
   <bean id = "student" class = "com.tutorialspoint.Student">
      <property name = "name"  value = "Zara" />
      <property name = "age"  value = "11"/>      
   </bean>

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

运行项目

创建源文件和配置文件后，运行应用程序。右键单击应用程序中的MainApp.java，然后使用以Java应用程序运行命令。如果应用程序一切正常，它将打印以下消息。

Name : Zara
Age : 11
Student profile setup complete.