使用动态代理解决上述问题
代理设计模式的原理: 使用一个代理将对象包装起来, 然后用该代理对象取代原始对象. 任何对原始对象的调用都要通过代理. 代理对象决定是否以及何时将方法调用转到原始对象上.
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 );
}
package com.learn.spring.aop;
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {
@Override
public int add(int i, int j) {
int result = i + j ;
return result;
}
@Override
public int sub(int i, int j) {
int result = i - j ;
return result;
}
@Override
public int mul(int i, int j) {
int result = i * j ;
return result;
}
@Override
public int div(int i, int j) {
int result = i / j ;
return result;
}
}
package com.learn.spring.aop;
public class ArithmeticCalculatorLoggingImpl implements ArithmeticCalculator {
@Override
public 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;
}
@Override
public 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;
}
@Override
public 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;
}
@Override
public 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;
//代理类
public class ArithmeticCalculatorLoggingProxy {
//1.被代理的对象 目标对象
private ArithmeticCalculator target ; // 实际上是ArithmeticCalculatorImpl对象.
//通过构造器的方式将目标对象传入
public ArithmeticCalculatorLoggingProxy(ArithmeticCalculator target){
this.target = target ;
}
//获取代理对象
public ArithmeticCalculator getLoggingProxy(){
//定义代理对象
ArithmeticCalculator proxy ;
/**
* loader: ClassLoader 类加载器
* interfaces: 目标类的所有接口,目的是获取接口中的方法
* h: InvocationHandler
*/
ClassLoader loader = target.getClass().getClassLoader();
Class[] interfaces = target.getClass().getInterfaces();
InvocationHandler h = new InvocationHandler() {
/**
* proxy:代理对象 在invoke方法中一般不会用
* method:正在调用的方法
* args:调用方法传入的参数
*/
@Override
public 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));
//执行目标方法
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) {
//目标对象
ArithmeticCalculator target = new ArithmeticCalculatorImpl();
//获取代理对象
ArithmeticCalculator proxy =
new ArithmeticCalculatorLoggingProxy(target).getLoggingProxy();
System.out.println("proxy:" + proxy.getClass().getName());
int result = proxy.add(1, 1); // 实际上要去执行invoke方法
System.out.println("result=====>"+result);
}
}