使用動態代理解決上述問題

代理設計模式的原理: 使用一個代理將對象包裝起來, 然后用該代理對象取代原始對象. 任何對原始對象的調用都要通過代理. 代理對象決定是否以及何時將方法調用轉到原始對象上.

package com.learn.spring.aop;public interface ArithmeticCalculator {public int add(int i, int j );public int sub(int i, int j );public int mul(int i, int j );public int div(int i, int j ); }

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package com.learn.spring.aop;public class ArithmeticCalculatorImpl implements ArithmeticCalculator {@Overridepublic int add(int i, int j) {int result = i + j ;return result;}@Overridepublic int sub(int i, int j) {int result = i - j ;return result; }@Overridepublic int mul(int i, int j) {int result = i * j ;return result;}@Overridepublic int div(int i, int j) {int result = i / j ;return result;}} package com.learn.spring.aop;public class ArithmeticCalculatorLoggingImpl implements ArithmeticCalculator {@Overridepublic int add(int i, int j) {//System.out.println("learn==>The method add begins with ["+i+","+j+"]");int result = i + j ;//System.out.println("learn==>The method add ends with "+ result );return result;}@Overridepublic int sub(int i, int j) {System.out.println("learn==>The method sub begins with ["+i+","+j+"]");int result = i - j ;System.out.println("learn==>The method sub ends with "+ result );return result; }@Overridepublic int mul(int i, int j) {System.out.println("learn==>The method mul begins with ["+i+","+j+"]");int result = i * j ;System.out.println("learn==>The method mul ends with "+ result );return result;}@Overridepublic int div(int i, int j) {System.out.println("learn==>The method div begins with ["+i+","+j+"]");int result = i / j ;System.out.println("learn==>The method div ends with "+ result );return result;}} package com.learn.spring.aop;import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.Arrays;//代理類 public class ArithmeticCalculatorLoggingProxy {//1.被代理的對象 目標對象private ArithmeticCalculator target ; // 實際上是ArithmeticCalculatorImpl對象.//通過構造器的方式將目標對象傳入public ArithmeticCalculatorLoggingProxy(ArithmeticCalculator target){this.target = target ;}//獲取代理對象public ArithmeticCalculator getLoggingProxy(){//定義代理對象ArithmeticCalculator proxy ;/*** loader: ClassLoader 類加載器* interfaces: 目標類的所有接口，目的是獲取接口中的方法* h: InvocationHandler*/ClassLoader loader = target.getClass().getClassLoader();Class[] interfaces = target.getClass().getInterfaces();InvocationHandler h = new InvocationHandler() {/*** proxy:代理對象 在invoke方法中一般不會用* method:正在調用的方法* args:調用方法傳入的參數*/@Overridepublic Object invoke(Object proxy, Method method, Object[] args)throws Throwable {String methodName = method.getName();//加日志System.out.println("learn===>The method "+methodName+" begins with "+ Arrays.asList(args));//執行目標方法Object result = method.invoke(target, args);//加日志System.out.println("learn===>The method "+methodName+" ends with " + result );return result;}};proxy = (ArithmeticCalculator)Proxy.newProxyInstance(loader, interfaces, h);return proxy ;}} package com.learn.spring.aop;public class Main {public static void main(String[] args) {//目標對象ArithmeticCalculator target = new ArithmeticCalculatorImpl();//獲取代理對象ArithmeticCalculator proxy = new ArithmeticCalculatorLoggingProxy(target).getLoggingProxy();System.out.println("proxy:" + proxy.getClass().getName());int result = proxy.add(1, 1); // 實際上要去執行invoke方法System.out.println("result=====>"+result);} }

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