09点睛Spring4.1-AOP

9.1 AOP

• AOP可以了让一组类共享相同的行为.在OOP中只能通过继承类和实现接口,这样使代码的耦合度增强,且类继承只能为单继承,阻碍更多行为添加到一组类上;
• 下面演示一个日志系统的实现,简单但不失表达AOP的核心内容
  • 演示通过注解拦截和通过方法规则拦截;
• 一些小术语
  • JoinPoint:你需要拦截的代码位置(代码里已标识)
  • Pointcut:符合某个条件后需要执行的代码位置(代码里已标识)

9.2 示例

采取2种截获方式:拦截注解和拦截方法

9.2.1 增加aspectj依赖到maven

<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjrt</artifactId>
    <version>1.8.5</version>
</dependency>
<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjweaver</artifactId>
    <version>1.8.5</version>
</dependency>

9.2.2 编写拦截规则的注解

package com.wisely.aop;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Action {
    String name();

}

9.2.3 编写需要拦截的2个测试bean

• 使用注解

package com.wisely.aop;

import org.springframework.stereotype.Service;

@Service
public class Demo1Service {
    @Action(name="demo1,add操作")
    public void add(){} //JoinPoint
    @Action(name="demo1,remove操作")
    public void remove(){}//JoinPoint
    @Action(name="demo1,update操作")
    public void update(){}//JoinPoint
    @Action(name="demo1,query操作")
    public void query(){}//JoinPoint

}

• 使用方法规则

package com.wisely.aop;

import org.springframework.stereotype.Service;

@Service
public class Demo2Service {
    public void add(){}//JoinPoint
    public void remove(){}//JoinPoint
    public void update(){}//JoinPoint
    public void query(){}//JoinPoint
}

9.2.4 编写切面

package com.wisely.aop;

import java.lang.reflect.Method;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class LogAspect {
    @After("@annotation(com.wisely.aop.Action)") //此处为pointcut
    public void after(JoinPoint joinPoint) {
        //每一个符合表达式条件的位置为joinPoint
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        Action action = method.getAnnotation(Action.class);
        System.out.println(action.name());
        //获得操作内容后可插入数据库中
    }

    @Before("execution(* com.wisely.aop.Demo2Service.*(..))") //此处为pointcut
    public void before(JoinPoint joinPoint){
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        System.out.println("demo2,"+method.getName());

    }
}

9.2.5 测试

package com.wisely.aop;

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

@Configuration
@EnableAspectJAutoProxy //开启对AspectJ的@Aspect注解的支持,别忘了
public class Main {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext("com.wisely.aop");
        Demo1Service d1s = context.getBean(Demo1Service.class);
        d1s.add();
        d1s.remove();
        d1s.update();
        d1s.query();

        Demo2Service d2s = context.getBean(Demo2Service.class);
        d2s.add();
        d2s.remove();
        d2s.update();
        d2s.query();
        context.close();
    }

}

输出结果

demo1,add操作
demo1,remove操作
demo1,update操作
demo1,query操作
demo2,add
demo2,remove
demo2,update
demo2,query