Around Advice

Around是一种通知类型，可确保在方法执行之前和之后运行建议。 以下是around建议的语法。

语法 (Syntax)

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

Where,

• PointCut-id - PointCut-id 。

• methodName - 在被调用函数之前调用的函数的方法名称。

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.ProceedingJoinPoint;
public class Logging {
   /** 
    * This is the method which I would like to execute
    * around a selected method execution.
    */
   public String aroundAdvice(ProceedingJoinPoint jp) throws Throwable{
      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();
   }   
}

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();    
   }
}

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:config>
      <aop:aspect id = "log" ref = "logging">
         <aop:PointCut id = "selectName" 
            expression = "execution(* cn.xnip.Student.getName(..))"/>
         <aop:around PointCut-ref = "selectName" method = "aroundAdvice"/>
      </aop:aspect>
   </aop:config>
   <!-- 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>

运行项目 (Run Project)

完成源和配置文件的创建后，运行您的应用程序。 右键单击应用程序中的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。

Around advice
Name : Zara
Returning Zara