spring_aop

普通代理的实现:

Buy.java

package com.proxyExample;

public interface Buy {

public void buyThing(String message);

}

BuyImpl.java

package com.proxyExample;

public class BuyImpl implements Buy {

public void buyThing(String message) {

System.out.println("我要买东西了^_^"+message);

}

}

BuyProxy.java

package com.proxyExample;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

public class BuyProxy implements InvocationHandler {

private Object obj;

public BuyProxy(Object obj) {

this.obj = obj;

}

public Object invoke(Object proxy, Method method, Object[] args)

throws Throwable {

System.out.println("开始调用被代理的类的方法、嘎嘎"+method);

method.invoke(obj, args);

System.out.println("结束调用被代理的类的方法、嘎嘎"+method);

return null;

}

}

Test.java

package com.proxyExample;

import java.lang.reflect.Proxy;

public class Test {

public static void main(String args[]) {

Buy bb = new BuyImpl();

BuyProxy pro = new BuyProxy(bb);

Buy go = (Buy) Proxy.newProxyInstance(bb.getClass().getClassLoader(),

bb.getClass().getInterfaces(), pro);

go.buyThing("买烤鸡，烤鸭，红烧牛排");

}

}

AOP代理的实现:

AOP在Spring中占有很重要的地位，做了一个例子是利用AOP来做一个登陆的身份验证，希望能对大家有所帮助，使用了AOP可以在不破坏你的代码的前提下帮你完成验证功能。

转一点AOP的知识：

1、Spring只支持方法拦截，也就是说，只能在方法的前后进行拦截，而不能在属性前后进行拦截。

2、Spring支持四种拦截类型：目标方法调用前（before），目标方法调用后（after），目标方法调用前后（around），以及目标方法抛出异常（throw）。

3、前置拦截的类必须实现MethodBeforeAdvice接口，实现其中的before方法。

4、后置拦截的类必须实现AfterReturningAdvice接口，实现其中的afterReturning方法。

5、前后拦截的类必须实现MethodInterceptor接口，实现其中的invoke方法。前后拦截是唯一可以控制目标方法是否被真正调用的拦截类型，也可以控制返回对象。而前置拦截或后置拦截不能控制，它们不能印象目标方法的调用和返回。

以上可以看出我们要选用实现MethodInterceptor接口的方法来完成这个功能

Student.java

package com.aop;

public interface Student {

public void addStudent(String name);

}

StudentImpl.java

package com.aop;

public class StudentImpl implements Student {

public void addStudent(String name) {

System.out.println("欢迎"+name+"来到spring");

}

}

BeforeAdvice.java

package com.aop;

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

public class BeforeAdvice implements MethodBeforeAdvice {

public void before(Method arg0, Object[] arg1, Object arg2) throws Throwable {

System.out.println(" 这是BeforeAdvice类的before方法. ");

}

}

AfterAdvice.java

package com.aop;

import java.lang.reflect.Method;

import org.springframework.aop.AfterReturningAdvice;

public class AfterAdvice implements AfterReturningAdvice {

public void afterReturning(Object arg0, Method arg1, Object[] arg2, Object arg3) throws Throwable {

System.out.println("这是AfterAdvice类的afterReturning方法.");

}

}

CompareInterceptor.java

package com.aop;

import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

public class CompareInterceptor implements MethodInterceptor {

public Object invoke(MethodInvocation arg0) throws Throwable {

Object result = null;

String stu_name = arg0.getArguments()[0].toString();

if (stu_name.equals("")||stu_name==null) {

result = arg0.proceed();

} else {

System.out.println("此学生是" + stu_name);

}

return result;

}

}

Test.java

package com.aop;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.FileSystemXmlApplicationContext;

public class Test {

public static void main(String[] args) {

ApplicationContext ctx = new FileSystemXmlApplicationContext("/src/applicationContext.xml");

Student s = (Student) ctx.getBean("student");

s.addStudent("kava");

}

}

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"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
<bean id="beforeAdvice" class="com.aop.BeforeAdvice"></bean>

<bean id="afterAdvice" class="com.aop.AfterAdvice"></bean>

<bean id="compareInterceptor" class="com.aop.CompareInterceptor"></bean>

<bean id="studenttarget" class="com.aop.StudentImpl"></bean>

<bean id="student"

class="org.springframework.aop.framework.ProxyFactoryBean">

<property name="proxyInterfaces">

<value>com.aop.Student</value>

</property>

<property name="interceptorNames">

<list>

<value>beforeAdvice</value>

<value>afterAdvice</value>

<value>compareInterceptor</value>

</list>

</property>

<property name="target">

<ref bean="studenttarget" />

</property>

</bean>

</beans>

对CompareInterceptor.java进行处理可以增加控制逻辑，实现权限控制

package com.aop;

import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

public class CompareInterceptor implements MethodInterceptor {

public Object invoke(MethodInvocation arg0) throws Throwable {

Object result = null;

String stu_name = arg0.getArguments()[0].toString();

if (stu_name.equals("")||stu_name==null) {

return mapping.findForward("login");

} else {

System.out.println("此学生是" + stu_name);

return result = arg0.proceed();

}

}

}

可参考例子:
http://lighter.javaeye.com/blog/42673 http://kukuqiu.javaeye.com/blog/163199