Spring实践之面向切面编程(AOP)

面向切面编程(AOP)

在运行时，动态地将代码切入到类的指定方法、指定位置上的编程思想就是面向切面的编程(Aspect Oriented Programming)。

实现

这里直接上代码, 具体原理后面写.

依赖

这里会使用@AspectJ来实现Spring AOP. 需要使用maven加载以下依赖.

 <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.9.RELEASE</version>
</dependency>
<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>4.3.9.RELEASE</version>
</dependency>
<dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.10</version>
</dependency>

代码结构：

代码

Worker.java

这个是需要被AOP的类, AOP可以动态地将代码插入到它的方法. 具体见下面的TimeRecordAspect.java

package spring.aop;

/**
 * @author ixuhangyi
 * @since 2017/7/18.
 */
public interface Worker {
    void work();
}

WorkerImpl.java

Worker类的实现

package spring.aop;

import org.springframework.stereotype.Service;

/**
 * @author ixuhangyi
 * @since 2017/7/18.
 */
@Service
public class WorkerImpl implements Worker {
    public void work() {
        System.out.println("working");
    }
}

TimeRecordAspect.java

package spring.aop;


import org.aspectj.lang.ProceedingJoinPoint;
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.cache.interceptor.CacheOperationInvoker;
import org.springframework.stereotype.Service;

/**
 * @author ixuhangyi
 * @since 2017/7/18.
 */
 // @Aspect 声明这是一个切面
@Service
@Aspect
public class TimeRecordAspect {
    // 在sprint.aop.WorkerImpl.work()方法中实现面向切面, 在方法调用前/调用后, 插入了记录时间的代码
    // 与@Around类似的有@Before, @After等
    @Around("execution(* spring.aop.WorkerImpl.work(..))")
    public void beforeWork(ProceedingJoinPoint point) throws Throwable {
        System.out.println("method start time:" + System.currentTimeMillis());
        Object object = point.proceed();
        System.out.println("method end time:" + System.currentTimeMillis());
    }
}

App.java

package spring.aop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

/**
 * @author ixuhangyi
 * @since 2017/7/18.
 */
@Configuration
@EnableAspectJAutoProxy
@ComponentScan
public class App {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(App.class);
        Worker worker = context.getBean(Worker.class);
        worker.work();
    }
}

运行结果

method start time:1500437326224
working
method end time:1500437326224

可以看到在不修改任何Worker.work()代码的情况下, 实现了动态增加代码的功能.