@AspectJ based

@AspectJ指的是将方面声明为使用Java 5注释注释的常规Java类的样式。 通过在基于XML模式的配置文件中包含以下元素来启用@AspectJ支持。

<aop:aspectj-autoproxy/>

您还需要在应用程序的类路径上使用以下AspectJ库。 这些库位于AspectJ安装的“lib”目录中，否则您可以从Internet下载它们。

• aspectjrt.jar
• aspectjweaver.jar
• aspectj.jar
• aopalliance.jar

宣布一个方面

Aspects类与任何其他普通bean一样，并且可以像任何其他类一样拥有方法和字段，除了它们将使用@Aspect进行注释，如下所示 -

package org.xyz;
import org.aspectj.lang.annotation.Aspect;
@Aspect
public class AspectModule {
}

它们将像任何其他bean一样配置为XML，如下所示 -

<bean id = "myAspect" class = "org.xyz.AspectModule">
   <!-- configure properties of aspect here as normal -->
</bean>

宣布切入点

pointcut有助于确定要用不同建议执行的感兴趣的连接点（即方法）。 在使用基于@ AspectJ的配置时，切入点声明有两个部分 -

• 切入点表达式，确切地确定我们感兴趣的方法执行。

• 包含名称和任意数量参数的切入点签名。 该方法的实际主体是无关紧要的，实际上应该是空的。

以下示例定义了一个名为“businessService”的切入点，该切入点将与com.xyz.myapp.service包下的类中可用的每个方法的执行相匹配 -

import org.aspectj.lang.annotation.Pointcut;
@Pointcut("execution(* com.xyz.myapp.service.*.*(..))") // expression 
private void businessService() {}  // signature

以下示例定义了一个名为“getname”的切入点，该切入点将与cn.xnip包下的Student类中可用的getName（）方法的执行相匹配 -

import org.aspectj.lang.annotation.Pointcut;
@Pointcut("execution(* cn.xnip.Student.getName(..))") 
private void getname() {}

声明建议

您可以使用代码段中给出的@ {ADVICE-NAME}注释声明五个建议中的任何一个。 这假定您已经定义了切入点签名方法businessService（） -

@Before("businessService()")
public void doBeforeTask(){
   ...
}
@After("businessService()")
public void doAfterTask(){
   ...
}
@AfterReturning(pointcut = "businessService()", returning = "retVal")
public void doAfterReturnningTask(Object retVal) {
   // you can intercept retVal here.
   ...
}
@AfterThrowing(pointcut = "businessService()", throwing = "ex")
public void doAfterThrowingTask(Exception ex) {
  // you can intercept thrown exception here.
  ...
}
@Around("businessService()")
public void doAroundTask(){
   ...
}

您可以为任何建议定义内联切入点。 以下是为建议之前定义内联切入点的示例 -

@Before("execution(* com.xyz.myapp.service.*.*(..))")
public doBeforeTask(){
   ...
}

@AspectJ基于AOP的例子

为了理解与基于@AspectJ的AOP相关的上述概念，让我们编写一个实现很少建议的例子。 要编写我们的示例并提供一些建议，让我们使用一个可用的Eclipse IDE并执行以下步骤来创建Spring应用程序 -

这是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。

package cn.xnip;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Around;
@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(* cn.xnip.*.*(..))")
   private void selectAll(){}
   /** 
      * This is the method which I would like to execute
      * before a selected method execution.
   */
   @Before("selectAll()")
   public void beforeAdvice(){
      System.out.println("Going to setup student profile.");
   }
   /** 
      * This is the method which I would like to execute
      * after a selected method execution.
   */
   @After("selectAll()")
   public void afterAdvice(){
      System.out.println("Student profile has been setup.");
   }
   /** 
      * This is the method which I would like to execute
      * when any method returns.
   */
   @AfterReturning(pointcut = "selectAll()", returning = "retVal")
   public void afterReturningAdvice(Object retVal){
      System.out.println("Returning:" + retVal.toString() );
   }
   /**
      * This is the method which I would like to execute
      * if there is an exception raised by any method.
   */
   @AfterThrowing(pointcut = "selectAll()", throwing = "ex")
   public void AfterThrowingAdvice(IllegalArgumentException ex){
      System.out.println("There has been an exception: " + ex.toString());   
   }
}

以下是Student.java文件的内容

package cn.xnip;
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 cn.xnip;
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();
      student.printThrowException();
   }
}

以下是配置文件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 ">
   <aop:aspectj-autoproxy/>
   <!-- Definition for student bean -->
   <bean id = "student" class = "cn.xnip.Student">
      <property name = "name" value = "Zara" />
      <property name = "age"  value = "11"/>      
   </bean>
   <!-- Definition for logging aspect -->
   <bean id = "logging" class = "cn.xnip.Logging"/> 
</beans>

完成源和bean配置文件的创建后，让我们运行应用程序。 如果您的应用程序一切正常，它将打印以下消息 -

Going to setup student profile.
Name : Zara
Student profile has been setup.
Returning:Zara
Going to setup student profile.
Age : 11
Student profile has been setup.
Returning:11
Going to setup student profile.
Exception raised
Student profile has been setup.
There has been an exception: java.lang.IllegalArgumentException
.....
other exception content