Spring AOP的注解实现

适用场景：

　　记录接口方法的执行情况，记录相关状态到日志中。

注解类：LogTag.java

package com.lichmama.spring.annotation;

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 LogTag {
    String value() default "";
}

@Target （使用）注解的目标类型：

CONSTRUCTOR        构造方法声明
FIELD              字段声明（包括枚举常量）
LOCAL_VARIABLE     局部变量声明
METHOD             方法声明
PACKAGE            包声明
PARAMETER          参数声明
TYPE               类、接口（包括注释类型）或枚举声明

@Retention 注解的生命周期（默认CLASS）：

CLASS　　　　　　　编译器将把注释记录在类文件中，但在运行时VM 不需要保留注释。
RUNTIME　　　　　　编译器将把注释记录在类文件中，在运行时VM 将保留注释，因此可以反射性地读取。
SOURCE　　　　　　 编译器要丢弃的注释。

@Documented 标记生成javadoc

切面类：ServiceAspect.java

package com.lichmama.spring.aop;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;

import com.lichmama.spring.annotation.LogTag;

@Aspect
@Component
public class ServiceAspect {

    private Log log = LogFactory.getLog(getClass());

    @Pointcut("@annotation(com.lichmama.spring.annotation.LogTag)")
    private void pointcut() {
    }

    @Before("pointcut()")
    public void doBefore(JoinPoint joinPoint) {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        String methodName = signature.getMethod().getName();
        String logTag = ((LogTag) signature.getMethod().getAnnotation(LogTag.class)).value();
        log.info("before calling " + methodName + ", value: " + logTag);
    }
}

@Pointcut("@annotation(com.lichmama.spring.annotation.LogTag)") 标注一个切入点，执行任意带有LogTag注解的方法触发。

业务实现：UserServiceImpl.java

package com.lichmama.spring.service.impl;

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

import com.lichmama.spring.annotation.LogTag;
import com.lichmama.spring.dao.IUserDAO;
import com.lichmama.spring.entity.User;
import com.lichmama.spring.service.IUserService;

@Service
public class UserServiceImpl implements IUserService {

    @Autowired
    private IUserDAO userDAO;

    @LogTag
    @Override
    public User getUserById(int id) {
        return userDAO.getUserById(id);
    }

    @LogTag
    @Override
    public void saveUser(User user) {
        userDAO.saveUser(user);
    }

    @LogTag
    @Override
    public void updateUser(User user) {
        userDAO.updateUser(user);
    }

    @LogTag("dangerous operation")
    @Override
    public void deleteUser(int id) {
        userDAO.deleteUser(id);
    }
}

spring配置文件：applicationContext.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: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-3.2.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.2.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop-3.2.xsd">

    <context:component-scan base-package="com.lichmama.spring.aop" />
    <context:component-scan base-package="com.lichmama.spring.dao" />
    <context:component-scan base-package="com.lichmama.spring.service" />

    <aop:aspectj-autoproxy proxy-target-class="true" />
</beans>

写个测试：

public class TestCase {

    private Log log = LogFactory.getLog(getClass());

    private ApplicationContext ctx;

    @Before
    public void initSpringContext() {
        ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }

    @Test
    public void testAOP() {
        IUserService userService = ctx.getBean(IUserService.class);

        userService.saveUser(new User(1, "lichmama"));
        userService.saveUser(new User(2, "james"));
        userService.saveUser(new User(3, "dwyane"));

        userService.updateUser(new User(2, "bill"));

        User user = userService.getUserById(2);
        log.info(user.toString());

        userService.deleteUser(1);
    }
}

16:06:22,517 INFO ServiceAspect:29 - before calling saveUser, value:
16:06:22,549 INFO ServiceAspect:29 - before calling saveUser, value:
16:06:22,549 INFO ServiceAspect:29 - before calling saveUser, value:
16:06:22,550 INFO ServiceAspect:29 - before calling updateUser, value:
16:06:22,551 INFO ServiceAspect:29 - before calling getUserById, value:
16:06:22,551 INFO TestSpring:35 - id: 2, name: bill
16:06:22,551 INFO ServiceAspect:29 - before calling deleteUser, value: dangerous operation