Spring AOP的幾個概念

1.切面(Aspect)：切面就是一個關注點的模組化，如事務管理、日誌管理、許可權管理等； 
2.連線點(Joinpoint)：程式執行時的某個特定的點，在Spring中就是一個方法的執行； 
3.通知(Advice)：通知就是在切面的某個連線點上執行的操作，也就是事務管理、日誌管理等； 
4.切入點(Pointcut)：切入點就是描述某一類選定的連線點，也就是指定某一類要織入通知的方法； 
5.目標物件(Target)：就是被AOP動態代理的目標物件； 

藉助下圖進行理解：

先來了解切面程式設計的使用

前置增強

建立一個前置增強類

package cjq.demo.spring.aop;

import
 
 org.springframework.aop.MethodBeforeAdvice;

import java.lang.reflect.Method;

/**
 * author: cjianquan
 * date: 2016/9/9
 */
public class GreetingBeforeAdvice implements MethodBeforeAdvice {
    @Override
    public void before(Method method, Object[] args, Object target) throws Throwable {
        System.out.println("GreetingBeforeAdvice Before"
 
);
    }

}

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後置增強

package cjq.demo.spring.aop;

import org.springframework.aop.AfterReturningAdvice;

import java.lang.reflect.Method;

/**
 * author: cjianquan
 * date: 2016/9/9
 */
public class GreetingAfterAdvice implements AfterReturningAdvice {
    @Override
    public void afterReturning
 
(Object result, Method method, Object[] args, Object target) throws Throwable {
        System.out.println("GreetingAfterAdvice After");
    }
}

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測試程式碼：

    @Test
    public void test_springAop(){
        ProxyFactory proxyFactory = new ProxyFactory();     // 建立代理工廠
        proxyFactory.setTarget(new GreetingImpl());         // 射入目標類物件
        proxyFactory.addAdvice(new GreetingBeforeAdvice()); // 新增前置增強
        proxyFactory.addAdvice(new GreetingAfterAdvice());  // 新增後置增強

        Greeting greeting = (Greeting) proxyFactory.getProxy(); // 從代理工廠中獲取代理
        greeting.sayHello("Jack");
    }

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當然，我們完全可以只定義一個增強類，讓它同時實現 MethodBeforeAdvice 與 AfterReturningAdvice 這兩個介面，如下

package cjq.demo.spring.aop;

import org.springframework.aop.AfterReturningAdvice;
import org.springframework.aop.MethodBeforeAdvice;

import java.lang.reflect.Method;

/**
 * author: cjianquan
 * date: 2016/9/9
 */
public class GreetingBeforeAndAfterAdvice implements MethodBeforeAdvice, AfterReturningAdvice {
    @Override
    public void before(Method method, Object[] args, Object target) throws Throwable {
        System.out.println(" GreetingBeforeAndAfterAdvice  Before");
    }

    @Override
    public void afterReturning(Object result, Method method, Object[] args, Object target) throws Throwable {
        System.out.println("GreetingBeforeAndAfterAdvice  After");
    }
}

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測試程式碼：

    @Test
    public void test_springAop1(){
        ProxyFactory proxyFactory = new ProxyFactory();     // 建立代理工廠
        proxyFactory.setTarget(new GreetingImpl());         // 射入目標類物件
        proxyFactory.addAdvice(new GreetingBeforeAndAfterAdvice()); // 新增增強

        Greeting greeting = (Greeting) proxyFactory.getProxy(); // 從代理工廠中獲取代理
        greeting.sayHello("Jack");
    }

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環繞增強

package cjq.demo.spring.aop;


import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.springframework.stereotype.Component;

/**
 * author: cjianquan
 * date: 2016/9/9
 */
@Component("greetingAroundAdvice")
public class GreetingAroundAdvice implements MethodInterceptor {
    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        before();
        Object result = invocation.proceed();
        after();
        return result;
    }

    private void before() {
        System.out.println("GreetingAroundAdvice  Before");
    }

    private void after() {
        System.out.println("GreetingAroundAdvice  After");
    }
}

1. <?xmlversion="1.0"encoding="UTF-8"?>
2. <beansxmlns="http://www.springframework.org/schema/beans"
3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:p="http://www.springframework.org/schema/p"
4.     xsi:schemaLocation="http://www.springframework.org/schema/beans   
5.      http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
6.     <beanid="greetingBefore"class="com.jike.spring.chapter10.aop.advice.WaiterBeforeAdvice"/>
7.     <beanid="greetingAfter"class="com.jike.spring.chapter10.aop.advice.WaiterAfterAdvice"/>
8.     <beanid="greetingAround"class="com.jike.spring.chapter10.aop.advice.WaiterAroundAdvice"/>
9.     <beanid="target"class="com.jike.spring.chapter10.aop.advice.NativeWaiter"/>
10.     <beanid="waiter"class="org.springframework.aop.framework.ProxyFactoryBean"
11.         p:proxyInterfaces="com.jike.spring.chapter10.aop.advice.Waiter"
12.         p:target-ref="target"p:interceptorNames="greetingAround"/>
13. </beans>

測試程式碼：

    @Test
    public void test_greetingAroundAdvice(){
        ProxyFactory proxyFactory = new ProxyFactory();     // 建立代理工廠
        proxyFactory.setTarget(new GreetingImpl());         // 射入目標類物件
        proxyFactory.addAdvice(new GreetingAroundAdvice()); // 新增增強

        Greeting greeting = (Greeting) proxyFactory.getProxy(); // 從代理工廠中獲取代理
        greeting.sayHello("Jack");
    }

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