Spring review--動態代理和AOP程式碼的演化

客戶端程式碼，首先通過容器例項化applicationContext.xml裡面的Bean,然後呼叫add方法。

<span style="font-size:14px;"><span style="font-size:14px;">public class Client {

	public static void main(String[] args) {
		BeanFactory factory =new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
		UserManager userManager =(UserManager)factory.getBean("userManager"); 
	 	userManager.addUser("wm", "123");
	}

}
</span></span>

SecurityHandler, 採用動態代理的時候，把具體的執行委託給了代理類進行執行。採用AOP了之後，設定切入點，觸發切入條件後，執行擴充套件操作，然後回撥，繼續執行之前的業務邏輯。

<span style="font-size:14px;"><span style="font-size:14px;">@Aspect
public class SecurityHandler  {

	//將橫切性關注點 模組化，刪除動態代理，定義Aspect
	/*private Object targetObject;
	public Object  createProxyInstance(Object targetObject){
		this.targetObject=targetObject;
		return Proxy.newProxyInstance(targetObject.getClass().getClassLoader(), 
							   targetObject.getClass().getInterfaces(),
							   this);
	}
	
	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		checkSecurity();
		
		//呼叫目標方法
		Object ret = method.invoke(targetObject , args);
		return ret;
	}*/
	
	//定義PointCut,PointCut的名稱為addMethod()，此方法沒有返回值和引數。該方法就是標識，不進行呼叫。
	@Pointcut("execution(* add*(..))")
	private void addMethod(){};
	
	
	/**
	 * 定義Advice,表示我們的Advice應用到哪些pointcut訂閱的JoinPoint上 
	 */
	@Before("addMethod()")
	public void checkSecurity(){
		System.out.println("------checkSecurity()-------");
	}

}</span></span>

UserManager，執行真正業務邏輯，需要實現的介面。

<span style="font-size:14px;"><span style="font-size:14px;">public interface UserManager {

	public void addUser(String name,String password);
	public void delUser(int userId);
	public String findUserById(int userId);
	public void modifyUser(int userId,String userName,String password);

}
</span></span>

UserManagerImpl，執行執行真正業務邏輯的具體實現。

<span style="font-size:14px;"><span style="font-size:14px;">public class UserManagerImpl implements UserManager {

	@Override
	public void addUser(String name, String password) {
		System.out.println("---UserManagerImpl.addUser()-----------");

	}

	@Override
	public void delUser(int userId) {
		System.out.println("---UserManagerImpl.delUser()-----------");

	}

	@Override
	public String findUserById(int userId) {
		System.out.println("---UserManagerImpl.findUserById()-----------");
		return "wm";
	}

	@Override
	public void modifyUser(int userId, String userName, String password) {
		System.out.println("---UserManagerImpl.modifyUser()-----------");

	}

}</span></span>

applicationContext.xml 對AOP和容器進行配置。

<span style="font-size:14px;"><span style="font-size:14px;"><?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:tx="http://www.springframework.org/schema/tx"
	     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"
           default-autowire="byName">
	
	<aop:aspectj-autoproxy/>
	
	<bean id="userManager" class="com.bjpowernode.spring.UserManagerImpl"/> 
	<bean id="securityHandler" class="com.bjpowernode.spring.SecurityHandler"/>

</beans> 

</span></span>

UserManagerImplProxy，開始使用的代理類，代理類跟被代理者都通過實現UserManager介面。新增Aop之後，代理類就不起作用了，就註釋掉了。

<span style="font-size:14px;"><span style="font-size:14px;">/*package com.bjpowernode.spring;

public class UserManagerImplProxy implements UserManager {

	private UserManager UserManager;
	
	public UserManagerImplProxy(UserManager userManager) {
		this.UserManager = userManager;
	}

	@Override
	public void addUser(String name, String password) {
		// TODO Auto-generated method stub

	}

	@Override
	public void delUser(int userId) {
		// TODO Auto-generated method stub

	}

	@Override
	public String findUserById(int userId) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public void modifyUser(int userId, String userName, String password) {
		// TODO Auto-generated method stub

	}

}
*/</span></span>

Spring配置AOP有多種形式，上面的配置方式是annotation方式，還可以採用xml配置方式。

SecurityHandler可以簡化成如下程式碼：

<span style="font-size:14px;">public class SecurityHandler  {

	public void addAddMethod(){
		
	}
	public void checkSecurity(){
		System.out.println("------checkSecurity()-------");
	}

}</span>

applicationContext.xml如下：

<span style="font-size:14px;"><?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:tx="http://www.springframework.org/schema/tx"
	     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"
           default-autowire="byName">
	
	
	<bean id="userManager" class="com.bjpowernode.spring.UserManagerImpl"/> 
	<bean id="securityHandler" class="com.bjpowernode.spring.SecurityHandler"/>
	
	<aop:config>
		<aop:aspect id="securityAspect" ref="securityHandler">
			<aop:pointcut id="addAddMethod" expression="execution(* add*(..))"/>
			<aop:before method="checkSecurity" pointcut-ref="addAddMethod"/>
		</aop:aspect>
	</aop:config>

</beans> </span>

Aop執行結果：

xml裡面對錶達式的配置多樣，常用的如下。某些包下面的類和某些包下面刪除和新增操作的類的Aop的配置：

<span style="font-size:14px;">execution(* com.bjpowernode.spring.*.* (..))</span>

<span style="font-size:14px;">execution(* com.bjpowernode.spring.*.add*(..)|| </span><span style="font-size: 14px; font-family: Arial, Helvetica, sans-serif;">com.bjpowernode.spring.*.del*(..))</span>