java 综合示例代码

it2022-05-06  0

package javaenhance.src.cn.itcast.day3; 

 

import java.lang.reflect.Constructor;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

import java.util.ArrayList;

import java.util.Collection;

public class ProxyTest

 

    /** 

     * @param args 

     */ 

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

        // TODO Auto-generated method stub 

        //接收两个参数,一个是后边参数的字节码的加载器,一个是所要实现代理的接口的字节码 

        Class clazzProxy1 = Proxy.getProxyClass(Collection.class.getClassLoader(), Collection.class); 

        System.out.println(clazzProxy1.getName());//打印代理的名字     $Proxy0 

         

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

        /*想打印出如下格式: 

         * $Proxy0() 

        $Proxy0(InvocationHandler,int)*/ 

        Constructor[] constructors = clazzProxy1.getConstructors();//获取代理的构造函数 

        for(Constructor constructor : constructors){ 

            String name = constructor.getName();//获取代理的构造函数的name 

            StringBuilder sBuilder = new StringBuilder(name); 

            sBuilder.append('('); 

            Class[] clazzParams = constructor.getParameterTypes();//获取代理的构造函数的参数 

            for(Class clazzParam : clazzParams){ 

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

            } 

            if(clazzParams!=null && clazzParams.length != 0)//稳妥的判断是否是一个参数,不是就删掉最后的, 

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

            sBuilder.append(')'); 

            System.out.println(sBuilder.toString());    //$Proxy0(java.lang.reflect.InvocationHandler)       

        } 

 

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

        /*$Proxy0() 

        $Proxy0(InvocationHandler,int)*/ 

        Method[] methods = clazzProxy1.getMethods();//获取代理身上的方法 

        for(Method method : methods){ 

            String name = method.getName(); 

            StringBuilder sBuilder = new StringBuilder(name); 

            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.toString());             

        } 

         

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

        //Object obj = clazzProxy1.newInstance(); 

               //方式一:通过接口的子类创建对象   

        Constructor constructor = 

clazzProxy1.getConstructor(InvocationHandler.class)

        //获取代理身上的构造函数 

        //创建内部类MyInvocationHandler1,目的是传递给代理的构造器 

        class MyInvocationHandler1 implements InvocationHandler{ 

 

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

                    throws Throwable { 

                // TODO Auto-generated method stub 

                return null; 

            } 

         

        } 

        //方式二:匿名内部类  

        Collection proxy1 = (Collection)constructor.newInstance(new MyInvocationHandler1()); 

         

        System.out.println(proxy1);//没有错误 

        proxy1.clear();//没有错误 

        //proxy1.size();报错,因为,代理调用size方法,其实是调用了MyInvocationHandler1中的invoke,他的返回值是null 

        //System.out.println("111111111111111");//调试用的 

         

        //用了匿名内部类的方法实现 

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

 

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

                    throws Throwable { 

                return null; 

            } 

             

        }); 

 

 

         

         

        /*下边这部分代码非常重要和精辟*/ 

        final ArrayList target = new ArrayList();            

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

        proxy3.add("zxx")

        proxy3.add("lhm")

        proxy3.add("bxd")

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

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

    } 

 

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

         

        //方式三,newProxyInstance这个方法需要三个参数,可以直接创建target的代理对象 

        Object proxy3 = Proxy.newProxyInstance( 

                target.getClass().getClassLoader(), 

                /*new Class[]{Collection.class},*/ 

                 

                //获取target上的接口 

                target.getClass().getInterfaces(), 

                new InvocationHandler(){ 

                 

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

                            throws Throwable { 

 

                        /*long beginTime = System.currentTimeMillis(); 

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

                        long endTime = System.currentTimeMillis(); 

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

                        return retVal;*/ 

                         

                        //把上边的代码封装到一个类中,让后调用该类的方法,就实现了方法的封装 

                        advice.beforeMethod(method); 

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

                        advice.afterMethod(method); 

                        return retVal;                       

                         

                    } 

                } 

                ); 

        return proxy3; 

    } 

 

} 

 

/*$Proxy0 

----------begin constructors list---------- 

$Proxy0(java.lang.reflect.InvocationHandler) 

----------begin methods list---------- 

hashCode() 

equals(java.lang.Object) 

toString() 

add(java.lang.Object) 

contains(java.lang.Object) 

isEmpty() 

size() 

toArray() 

toArray([Ljava.lang.Object;) 

addAll(java.util.Collection) 

iterator() 

remove(java.lang.Object) 

clear() 

containsAll(java.util.Collection) 

removeAll(java.util.Collection) 

retainAll(java.util.Collection) 

getProxyClass(java.lang.ClassLoader,[Ljava.lang.Class;) 

newProxyInstance(java.lang.ClassLoader,[Ljava.lang.Class;,java.lang.reflect.InvocationHandler) 

isProxyClass(java.lang.Class) 

getInvocationHandler(java.lang.Object) 

getClass() 

notify() 

notifyAll() 

wait(long) 

wait(long,int

wait() 

----------begin create instance object---------- 

null 

到传智播客来学习啦! 

从传智播客毕业上班啦! 

add running time of 0 

到传智播客来学习啦! 

从传智播客毕业上班啦! 

add running time of 0 

到传智播客来学习啦! 

从传智播客毕业上班啦! 

add running time of 0 

到传智播客来学习啦! 

从传智播客毕业上班啦! 

size running time of 0 

$Proxy1*/ 

 

 

--------------------------------------------- 

import java.lang.reflect.Method

 

public interface Advice

    void beforeMethod(Method method); 

    void afterMethod(Method method); 

 

--------------------------------------------- 

package javaenhance.src.cn.itcast.day3; 

 

import java.lang.reflect.Method

//创建实现Advice接口的子类  

public class MyAdvice implements Advice { 

    long beginTime = 0; 

    public void afterMethod(Method method) { 

        // TODO Auto-generated method stub 

        System.out.println("从传智播客毕业上班啦!");       

        long endTime = System.currentTimeMillis(); 

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

 

    } 

 

    public void beforeMethod(Method method) { 

        // TODO Auto-generated method stub 

        System.out.println("到传智播客来学习啦!"); 

        beginTime = System.currentTimeMillis(); 

    } 

}

转载于:https://www.cnblogs.com/fanweisheng/p/11137871.html

相关资源:java的100个小程序(算法,API,面向对象 的综合题库)

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