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Spring AOP的注解实现
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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
