Spring 中基于 AOP 的 XML架构

Posted 2020-11-27 爱吃西瓜的番茄酱

Spring 中基于 AOP 的 XML架构

为了使用 aop 命名空间标签，你需要导入 spring-aop j架构，如下所述：

<?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 ">

   <!-- bean definition & AOP specific configuration -->

</beans>

确保项目中有如下四个库文件：

• aspectjrt.jar

• aspectjweaver.jar

• aspectj.jar

• aopalliance.jar

声明一个 aspect

一个 aspect 是使用 <aop:aspect></aop:aspect> 元素声明的，支持的 bean 是使用 ref 属性引用的，如下所示：

<aop:config>
   <aop:aspect id="myAspect" ref="aBean">
   ...
   </aop:aspect>
</aop:config>
<bean id="aBean" class="...">
...
</bean>

这里，“aBean” 将被配置和依赖注入.

声明一个切入点

使用元素<aop:pointcut>声明一个切入点.

一个切入点有助于确定使用不同建议执行的感兴趣的连接点（即方法）。在处理基于配置的 XML 架构时，切入点将会按照如下所示定义：

<aop:config>
   <aop:aspect id="myAspect" ref="aBean">
   <aop:pointcut id="businessService"
      expression="execution(* com.xyz.myapp.service.*.*(..))"/>
   ...
   </aop:aspect>
</aop:config>
<bean id="aBean" class="...">
...
</bean>

下面的示例定义了一个名为 “businessService” 的切入点，该切入点将与 com.tutorialspoint 包下的 Student 类中的 getName() 方法相匹配：

<aop:config>
   <aop:aspect id="myAspect" ref="aBean">
   <aop:pointcut id="businessService"
      expression="execution(* com.tutorialspoint.Student.getName(..))"/>
   ...
   </aop:aspect>
</aop:config>
<bean id="aBean" class="...">
...
</bean>

声明建议

你可以使用 <aop:{ADVICE NAME}> 元素在一个 中声明五个建议中的任何一个，如下所示：

<aop:config>
   <aop:aspect id="myAspect" ref="aBean">
      <aop:pointcut id="businessService"
         expression="execution(* com.xyz.myapp.service.*.*(..))"/>
      <!-- a before advice definition -->
      <aop:before pointcut-ref="businessService" 
         method="doRequiredTask"/>
      <!-- an after advice definition -->
      <aop:after pointcut-ref="businessService" 
         method="doRequiredTask"/>
      <!-- an after-returning advice definition -->
      <!--The doRequiredTask method must have parameter named retVal -->
      <aop:after-returning pointcut-ref="businessService"
         returning="retVal"
         method="doRequiredTask"/>
      <!-- an after-throwing advice definition -->
      <!--The doRequiredTask method must have parameter named ex -->
      <aop:after-throwing pointcut-ref="businessService"
         throwing="ex"
         method="doRequiredTask"/>
      <!-- an around advice definition -->
      <aop:around pointcut-ref="businessService" 
         method="doRequiredTask"/>
   ...
   </aop:aspect>
</aop:config>
<bean id="aBean" class="...">
...
</bean>

基于 AOP 的 XML 架构的示例

• 新建Spring项目

• 在项目中添加 Spring AOP 指定的库文件 aspectjrt.jar，aspectjweaver.jar 和 aspectj.jar。

• 创建 Java 类 Logging， Student 和 MainApp

这里是 Logging.java 文件的内容。这实际上是 aspect 模块的一个示例，它定义了在各个点调用的方法。

package hello;

//import org.springframework.aop.aspectj.AspectJAfterThrowingAdvice;

public class Logging {
    /**
     * This is the method which I would like to execute
     * before a selected method execution.
     */
    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.
     */
    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.
     */
    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.
     */
    public void AfterThrowingAdvice(IllegalArgumentException ex){
        System.out.println("there has been an exception:"+ex.toString());
    }
}

下面是 Student.java 文件的内容：

package hello;
//import org.springframework.beans.factory.annotation.Autowired;

public class Student {
    private int age;
    private String name;
    public void setAge(int age){
        this.age = age;
    }
    public int 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();
    }
}

下面是 MainApp.java 文件的内容：

package hello;
//import org.springframework.context.support.AbstractApplicationContext;
//import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
//import org.springframework.context.annotation.*;

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();
    }
}

下面是配置文件 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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/aop
       http://www.springframework.org/schema/aop/spring-aop.xsd">

    <aop:config>
        <aop:aspect id="log" ref="logging">
            <aop:pointcut id="selectAll" expression="execution(* hello.*.*(..))"/>
            <aop:before pointcut-ref="selectAll" method="beforeAdvice"/>
            <aop:after pointcut-ref="selectAll" method="afterAdvice"/>
            <aop:after-returning pointcut-ref="selectAll"
                                 returning="retVal"
                                 method="afterReturningAdvice"/>
            <aop:after-throwing pointcut-ref="selectAll"
                                throwing="ex"
                                method="AfterThrowingAdvice"/>
        </aop:aspect>
    </aop:config>

    <!-- Definition for student bean -->
    <bean id="student" class="hello.Student">
        <property name="name" value="番茄"/>
        <property name="age" value="10"/>
    </bean>

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

</beans>

运行一下应用程序

Going to setup student profile.
name:番茄
Student profile has been setup
Returning:番茄
Going to setup student profile.
age:10
Student profile has been setup
Returning:10
Going to setup student profile.
Exception raised
Student profile has been setup

注意：一定要保证项目下有库文件aspectjrt.jar和aspectjweaver.jar，否则会报错。

每天学习一点点，每天进步一点点。