动态代理-编写可生成代理和插入通告的通用方法

最新推荐文章于 2022-03-17 15:03:00 发布

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文章标签：

#constructor #object #class #methods #import #exception

本文介绍了一个使用Java反射API实现的动态代理示例，通过创建代理类并实现InvocationHandler接口来拦截目标方法调用，展示了如何生成代理实例及执行前后通知。

动态代理-编写可生成代理和插入通告的通用方法

package com.itcast.javaenhance.day3;

import java.lang.reflect.Constructor;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

import java.util.ArrayList;

import java.util.Collection;

public class ProxyTest {

public static void main(String[] args) throws Exception {

Class clazzProxy = Proxy.getProxyClass(

Collection.class.getClassLoader(), Collection.class);

System.out.println(clazzProxy.getName());

System.out.println("--------begin costructors list--------");

Constructor[] constructors = clazzProxy.getConstructors();

for(Constructor constructor: constructors) {

StringBuilder sBuilder = new StringBuilder(constructor.getName());

sBuilder.append('(');

Class[] clazzParams = constructor.getParameterTypes();

for(Class clazzParam: clazzParams) {

sBuilder.append(clazzParam.getName()).append(',');

}

if(clazzParams!=null&&clazzParams.length!=0) {

sBuilder.deleteCharAt(sBuilder.length()-1);

}

sBuilder.append(')');

System.out.println(sBuilder);

}

System.out.println("--------begin methods list--------");

Method[] methods = clazzProxy.getMethods();

for(Method method: methods) {

StringBuilder sBuilder = new StringBuilder(method.getName());

sBuilder.append('(');

Class[] clazzParams = method.getParameterTypes();

for(Class clazzParam: clazzParams) {

sBuilder.append(clazzParam.getName()).append(',');

}

if(clazzParams!=null&&clazzParams.length!=0) {

sBuilder.deleteCharAt(sBuilder.length()-1);

}

sBuilder.append(')');

System.out.println(sBuilder);

}

System.out.println("--------begin create instance object--------");

Constructor constructor2 = clazzProxy.getConstructor(InvocationHandler.class);

class MyInvocationHandler implements InvocationHandler {

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

throws Throwable {

return null;

}

Collection proxy = (Collection) constructor2.newInstance(new MyInvocationHandler());

System.out.println(proxy);

proxy.clear();

//proxy.size();

Collection proxy2 = (Collection) constructor2.newInstance(new InvocationHandler() {

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

throws Throwable {

return null;

}

});

final ArrayList target = new ArrayList();

Collection proxy3 = (Collection) getProxy(target, new MyAdvice());

proxy3.add("lhm");

proxy3.add("zxx");

proxy3.add("flx");

System.out.println(proxy3.size());

System.out.println(proxy3.getClass().getName());

}

private static Object getProxy(final Object target, final Advice advice) {

Object proxy3 = Proxy.newProxyInstance(

target.getClass().getClassLoader(),

target.getClass().getInterfaces(),

new InvocationHandler() {

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

throws Throwable {

advice.beforeMethod(method);

Object retVal = method.invoke(target, args);

advice.afterMethod(method);

return retVal;

}

);

return proxy3;

}

package com.itcast.javaenhance.day3;

import java.lang.reflect.Method;

public interface Advice {

void beforeMethod(Method method);

void afterMethod(Method method);

}

package com.itcast.javaenhance.day3;

import java.lang.reflect.Method;

public class MyAdvice implements Advice {

long beginTime;

@Override

public void afterMethod(Method method) {

long endTime = System.currentTimeMillis();

System.out.println(method.getName()+" running out of "+(endTime-beginTime));

System.out.println("从传智播客毕业上班了");

}

@Override

public void beforeMethod(Method method) {

System.out.println("到传智博客开始学习了");

beginTime = System.currentTimeMillis();

}