AOP（Aspect Orient Programming），我們一般稱為面向方面（切面）編程，作為面向對象的一種補充，用於處理系統中分布於各個模塊的橫切關註點，比如事務管理、日誌、緩存等等。AOP實現的關鍵在於AOP框架自動創建的AOP代理，AOP代理主要分為靜態代理和動態代理，靜態代理的代表為AspectJ；而動態代理則以Spring AOP為代表。

AOP配置示例：

數據訪問層：

package com.hanqi.dao;

public class AppuserDao {
	public int deleteUser(int ids) {
		System.out.println(ids +"被刪除");
		yichang();//拋出一個異常
		return 1;
	}
	public void yichang() {
		throw new RuntimeException("出現錯誤！");
	}
}

切面代理層：

package com.hanqi.util;

public class LogginProxy {
	public void beforeMethod() {
		System.out.println("方法之前被調用！");
	}

	public void afterMethod() {
		System.out.println("方法之後被調用！");
	}

	public void returnMethod() {
		System.out.println("返回結果時被調用！");
	}

	public void throwMethod() {
		System.out.println("拋出異常時被調用！");
	}
	/*public void aroundMethod() {
		System.out.println("方法被調用");
	}*/
}

spring.xml配置AOP

?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd">
	<bean id="logginProxy" class="com.hanqi.util.LogginProxy"></bean>
	<bean id="appuserdao" class="com.hanqi.dao.AppuserDao"></bean>
	<aop:config>
		<!-- 配置切點 -->
		<aop:pointcut
			expression="execution(* com.hanqi.dao.*.*(..))" id="aoppointcut" /><!--execution:執行，這句意為在執行com.hanqi.dao下的所有類時都會執行切面類-->
		<!-- 指明切面類 -->
		<aop:aspect ref="logginProxy">
			<aop:before method="beforeMethod"  pointcut-ref="aoppointcut"/>
			<aop:after method="afterMethod" pointcut-ref="aoppointcut"/>
			<aop:after-returning method="returnMethod" pointcut-ref="aoppointcut"/>
			<aop:after-throwing method="throwMethod" pointcut-ref="aoppointcut"/>	
		</aop:aspect>
	</aop:config>
</beans>

JUnit Test測試：

package com.hanqi.util;

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.hanqi.dao.AppuserDao;

class JUnittest {
	private ClassPathXmlApplicationContext c;
	private AppuserDao appuserdao;
	@BeforeEach
	void setUp() throws Exception {
		c = new ClassPathXmlApplicationContext("spring.xml");
		appuserdao = c.getBean(AppuserDao.class);
	}

	@AfterEach
	void tearDown() throws Exception {
		c.close();
	}

	@Test
	void test() {
		appuserdao.deleteUser(55);
	}

}

打印結果：

使用註解配置AOP

spring.xml配置：

<?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:aop="http://www.springframework.org/schema/aop"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd">
	<context:component-scan base-package="com.hanqi"></context:component-scan><!--配置掃描器-->
</beans>

數據訪問層：

package com.hanqi.dao;

import org.springframework.stereotype.Repository;

@Repository//加到spring容器中，id名默認為類名首字母小寫
public class AppuserDao {
	public int deleteUser(int ids) {
		System.out.println(ids +"被刪除");
		yichang();
		return 1;
	}
	public void yichang() {
		throw new RuntimeException("出現錯誤！");
	}
}

AppuserService類：

package com.hanqi.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Repository;

import com.hanqi.dao.AppuserDao;
@Repository
public class AppuserService {
	@Autowired//將該類自動放到當前類中的成員變量中，默認的裝配類型時byType
	//@Qualifier("dao")該註解可將bean中id="dao"的類裝配到該成員變量中，用於區分當類型相同時；
	private AppuserDao appuserDao;
	
	public int deleteUser(int ids) {
		return appuserDao.deleteUser(ids);
	}
}

代理類：

package com.hanqi.util;

import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.stereotype.Repository;

@Repository//加到spring容器中，id名為類名首字母小寫
@Aspect//聲明當前類為切面類
@EnableAspectJAutoProxy//自動代理
public class LogginProxy {
	@Before("execution(* com.hanqi.dao.*.*(..))")//聲明切點
	public void beforeMethod() {
		System.out.println("方法之前被調用！");
	}
	@After("execution(* com.hanqi.dao.*.*(..))")
	public void afterMethod() {
		System.out.println("方法之後被調用！");
	}
	@AfterReturning("execution(* com.hanqi.dao.*.*(..))")
	public void returnMethod() {
		System.out.println("返回結果時被調用！");
	}
	@AfterThrowing("execution(* com.hanqi.dao.*.*(..))")
	public void throwMethod() {
		System.out.println("拋出異常時被調用！");
	}
	/*public void aroundMethod() {
		System.out.println("方法被調用");
	}*/
}

測試類：

package com.hanqi.util;

import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.hanqi.dao.AppuserDao;
import com.hanqi.service.AppuserService;

class JUnittest {
	private ClassPathXmlApplicationContext c;
	private AppuserDao appuserdao;
	private AppuserService appuserService;
	@BeforeEach
	void setUp() throws Exception {
		c = new ClassPathXmlApplicationContext("spring.xml");
		//appuserdao = c.getBean(AppuserDao.class);
		appuserService = c.getBean(AppuserService.class);
	}

	@AfterEach
	void tearDown() throws Exception {
		c.close();
	}

	@Test
	void test() {
		//appuserdao.deleteUser(55);
		appuserService.deleteUser(66);
	}

}

JAVA 框架-Spring-AOP面向切面