spring AOP简单入门

2022-02-19 10:51:33

AOP(aspect oriented programming)面向切面编程。

大致意思是在方法的执行过程中织入其他要执行的方法。

项目结构图

先介绍一下通过代理的方式实现aop，几个文件和上一篇一样，再贴一遍方便观看

package com.ouc.wkp.model;

public class User {

    private String username;

    private String password;

    public String getUsername() {

        return username;

    }

    public void setUsername(String username) {

        this.username = username;

    }

    public String getPassword() {

        return password;

    }

    public void setPassword(String password) {

        this.password = password;

    }

}

User.java

package com.ouc.wkp.dao;

import com.ouc.wkp.model.User;

public interface UserDAO {

    public void save(User user);

    public void delete();

}

UserDAO.java

package com.ouc.wkp.dao.impl;

import org.springframework.stereotype.Component;

import com.ouc.wkp.dao.UserDAO;

import com.ouc.wkp.model.User;

@Component("u")

public class UserDAOImpl implements UserDAO {

    @Override

    public void save(User user) {

        // Hibernate

        // JDBC

        // XML

        // NetWork

        System.out.println("user saved!");

//        throw new RuntimeException();

    }

    @Override

    public void delete() {

        // TODO Auto-generated method stub

    }

}

UserDAOImpl.java

package com.ouc.wkp.service;

import javax.annotation.PostConstruct;

import javax.annotation.PreDestroy;

import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.beans.factory.annotation.Qualifier;

import org.springframework.stereotype.Component;

import com.ouc.wkp.dao.UserDAO;

import com.ouc.wkp.model.User;

@Component("userService")

public class UserService {

    private UserDAO userDAO;

    @PostConstruct

    public void init() {

        System.out.println("init");

    }

    public void add(User user) {

        userDAO.save(user);

    }

    public UserDAO getUserDAO() {

        return userDAO;

    }

    // @Autowired @Qualifier("u")

    @Resource(name = "u")

    public void setUserDAO(UserDAO userDAO) {

        this.userDAO = userDAO;

    }

    @PreDestroy

    public void destroy() {

        System.out.println("destroy");

    }

}

UserService.java

然后是一个代理类,继承自InvocationHandler

package com.ouc.wkp.aop;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

public class LogIntercepter implements InvocationHandler{

    private Object target;

    public Object getTarget() {

        return target;

    }

    public void setTarget(Object target) {

        this.target = target;

    }

    public void beforeMethod(Method m){

        System.out.println(m.getName()+" start");

    }

    public void afterMethod(Method m){

        System.out.println(m.getName()+" end");

    }

    public Object invoke(Object proxy,Method m,Object[] args) throws Throwable{

        beforeMethod(m);

        m.invoke(target, args);

        afterMethod(m);

        return null;

    }

}

LogIntercepter.java

然后再测试类中进行如下调用

@Test

    public void testProxy() {

        UserDAO userDAO = new UserDAOImpl();

        LogIntercepter li = new LogIntercepter();

        li.setTarget(userDAO);

        UserDAO userDAOProxy = (UserDAO) Proxy.newProxyInstance(userDAO

                .getClass().getClassLoader(), userDAO.getClass()

                .getInterfaces(), li);

        System.out.println(userDAOProxy.getClass());

        userDAOProxy.delete();

        userDAOProxy.save(new User());

    }

UserServiceTest.java

运行结果

然后介绍通过xml配置文件实现aop

使用aop需要一下
xmlns:aop="http://www.springframework.org/schema/aop"
http://www.springframework.org/schema/aop -->
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd">
<aop:aspectj-autoproxy />

还需要这个开启对com.ouc.wkp包下面的扫描

<context:component-scan base-package="com.ouc.wkp"></context:component-scan>

<?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:context="http://www.springframework.org/schema/context"

    xmlns:aop="http://www.springframework.org/schema/aop"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

            http://www.springframework.org/schema/beans/spring-beans-3.1.xsd

            http://www.springframework.org/schema/context

            http://www.springframework.org/schema/context/spring-context-3.1.xsd

            http://www.springframework.org/schema/aop

            http://www.springframework.org/schema/aop/spring-aop-3.1.xsd">

    <context:annotation-config />

    <!-- 使用注解需要下面四条 -->

    <!-- xmlns:context="http://www.springframework.org/schema/context" -->

    <!-- http://www.springframework.org/schema/context -->

    <!-- http://www.springframework.org/schema/context/spring-context-3.1.xsd"> -->

    <!-- <context:annotation-config /> -->

    <!-- 使用aop需要一下 -->

    <!-- xmlns:aop="http://www.springframework.org/schema/aop" -->

    <!-- http://www.springframework.org/schema/aop -->

    <!-- http://www.springframework.org/schema/aop/spring-aop-2.5.xsd"> -->

    <!-- <aop:aspectj-autoproxy /> -->

    <!-- 扫描 -->

    <context:component-scan base-package="com.ouc.wkp"></context:component-scan>

    <aop:aspectj-autoproxy />

    <bean id="logIntercepter2" class="com.ouc.wkp.aop.LogIntercepter2"></bean>

    <aop:config>

        <!-- <aop:pointcut expression="execution(public * com.ouc.wkp.service..*.add(..))"

            id="servicePointcut"/> -->

        <!-- <aop:aspect id="logAspect" ref="logIntercepter"> -->

        <!-- <aop:before method="before" pointcut="servicePointcut"/> -->

        <!-- </aop:aspect> -->

        <aop:aspect id="logAspect" ref="logIntercepter2">

            <aop:before method="before"

                pointcut="execution(public * com.ouc.wkp.service..*.add(..))" />

        </aop:aspect>

    </aop:config>

</beans>

beans.xml

看下面这段第一行声明了一个代理切入类（表达不准确）

<aop:pointcut expression="execution(public * com.ouc.wkp.service..*.add(..))"
id="servicePointcut"/>标识定义一个切入点pointcut。

<aop:before method="before" pointcut="servicePointcut"/>表示before织入这个切入点。

execution(public * com.ouc.wkp.service..*.add(..))代表com.ouc.wkp.service包下的任意包的任意类的add方法。

然后我们看代理切入类

package com.ouc.wkp.aop;

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.AfterReturning;

import org.aspectj.lang.annotation.AfterThrowing;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

import org.aspectj.lang.annotation.Pointcut;

import org.springframework.stereotype.Component;

@Aspect

@Component

public class LogIntercepter2 {

//    @Pointcut("execution(public * com.ouc.wkp.service..*.add(..))")

    public void myMethod(){};

//    @Before("myMethod()")

    public void before() {

        System.out.println("method before");

    }

//    @AfterReturning("execution(public * com.ouc.wkp.dao..*.*(..))")

    public void afterReturning(){

        System.out.println("method after returning");

    }

//    @AfterThrowing("myMethod()")

    public void afterThrowing(){

        System.out.println("method after throwing");

    }

//    @Around("myMethod()")

    public void aroundMethod(ProceedingJoinPoint pjp) throws Throwable{

        System.out.println("method around start");

        pjp.proceed();

        System.out.println("method around end");

    }

}

LogIntercepter2.java

类的开头需要加上

@Aspect
@Component

测试方法

@Test

    public void testAdd() throws Exception {

        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext(

                "beans.xml");

        UserService service = (UserService) ctx.getBean("userService");

        User user = new User();

        user.setUsername("qqq");

        user.setPassword("123ppp");

        //是一个代理

        System.out.println(service.getClass());

        service.add(user);

        ctx.destroy();

    }

UserServiceTest.java

运行结果

我们看到我们获得的userservice实质上是一个代理类

最后介绍通过注解实现aop，LogIntercepter2的代码再贴一遍.

beans.xml里面的<aop:config>可以注释掉

package com.ouc.wkp.aop;

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.AfterReturning;

import org.aspectj.lang.annotation.AfterThrowing;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

import org.aspectj.lang.annotation.Pointcut;

import org.springframework.stereotype.Component;

@Aspect

@Component

public class LogIntercepter2 {

    @Pointcut("execution(public * com.ouc.wkp.service..*.add(..))")

    public void myMethod(){};

    @Before("myMethod()")

    public void before() {

        System.out.println("method before");

    }

    @AfterReturning("execution(public * com.ouc.wkp.dao..*.*(..))")

    public void afterReturning(){

        System.out.println("method after returning");

    }

    @AfterThrowing("myMethod()")

    public void afterThrowing(){

        System.out.println("method after throwing");

    }

    @Around("myMethod()")

    public void aroundMethod(ProceedingJoinPoint pjp) throws Throwable{

        System.out.println("method around start");

        pjp.proceed();

        System.out.println("method around end");

    }

}

LogIntercepter2.java

@Pointcut("execution(public * com.ouc.wkp.service..*.add(..))")

public void myMethod(){};表示定义一个切入点

@Before("myMethod()")表示在方法执行前执行注解下面的方法 myMethod()为上面定义的切入点

后面的注解见名知意

运行结果

感觉还是很神奇的以前一直不理解什么是面向切面。现在简单了解了一下觉得很有趣，但是还是无法用语言准确表达出来= =

下一篇介绍spring整合hibernate

码农公寓

相关文章