【尚硅谷】spring学习笔记（14）：spring AOP基础-动态代理

• 代码混乱：越来越多的非业务需求(日志和验证等)加入后, 原有的业务方法急剧膨胀.  每个方法在处理核心逻辑的同时还必须兼顾其他多个关注点. 
• 代码分散: 以日志需求为例, 只是为了满足这个单一需求, 就不得不在多个模块（方法）里多次重复相同的日志代码. 如果日志需求发生变化, 必须修改所有模块.

动态代理：

package com.atguigu.spring.aop;

public interface ArithmeticCalculator1 {
	
	int add(int i ,int j);
	int sub(int i ,int j);
	
	int mul(int i, int j);
	int div(int i, int j);
}

package com.atguigu.spring.aop;

import org.springframework.stereotype.Component;

@Component("arithmeticCalculator")
public class ArithmeticCalculatorImpl1 implements ArithmeticCalculator1 {

	@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.atguigu.spring.aop;

import org.springframework.stereotype.Component;

@Component("arithmeticCalculator")
public class ArithmeticCalculatorLoggingImpl1 implements ArithmeticCalculator1 {

	@Override
	public int add(int i, int j) {
		System.out.println("The method add begins with[" + i + "," + j + "]");
		int result = i + j;
		System.out.println("The method add end with[" + result);
		return result;
	}

	@Override
	public int sub(int i, int j) {
		System.out.println("The method sub begins with[" + i + "," + j + "]");
		int result = i - j;
		System.out.println("The method sub end with[" + result);
		return result;
	}

	@Override
	public int mul(int i, int j) {
		System.out.println("The method mul begins with[" + i + "," + j + "]");
		int result = i * j;
		System.out.println("The method mul end with[" + result);
		return result;
	}

	@Override
	public int div(int i, int j) {
		System.out.println("The method div begins with[" + i + "," + j + "]");
		int result = i / j;
		System.out.println("The method div end with[" + result);
		return result;
	}


}

package com.atguigu.spring.aop;

import java.lang.reflect.Array;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;

import org.springframework.jmx.access.InvalidInvocationException;

public class ArithmeticCalculatorLoggingProxy {
	
	//要代理的对象
	private ArithmeticCalculator1 target;
	
	
	public ArithmeticCalculatorLoggingProxy(ArithmeticCalculator1 target){
		this.target = target;
	}
	
	public ArithmeticCalculator1 getLoggingProxy() {
		ArithmeticCalculator1 proxy = null;
		
		//代理对象由哪一个类加载器负责加载
		ClassLoader loader = target.getClass().getClassLoader();
		//代理对象的类型，即其中有哪些方法
		Class [] interfaces = new Class[]{ArithmeticCalculator1.class};
		//当调用代理对象其中的方法时，该执行的代码
		InvocationHandler h = new InvocationHandler() {
			
			/**
			 * proxy:正在还回的那个代理对象，一般情况下，在invoke方法中都不使用该对象
			 * method:正在被调用的方法
			 * args:调用方法时，传入的参数
			 * 
			 */
			
			@Override
			public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
				String methodName = method.getName();
				//日志
				System.out.println("The method" + methodName + "begins with" + Arrays.asList(args));
				//执行方法
				Object result = method.invoke(target, args); 
				//日志
				System.out.println("");
				System.out.println("The method" + methodName + "begins with" + result);
				return result;
			}
		};
		
		proxy = (ArithmeticCalculator1) Proxy.newProxyInstance(loader, interfaces, h);
		return proxy;
		
	}
 	
	

}

package com.atguigu.spring.aop;

public class Main {
	
	public static void main(String[] args) {
		
		
		ArithmeticCalculator1 target = new ArithmeticCalculatorImpl1();
		ArithmeticCalculator1 proxy = (ArithmeticCalculator1) new ArithmeticCalculatorLoggingProxy(target).getLoggingProxy();
		
		int result = proxy.add(1, 2);
		System.out.println("-->" + result);
		
		
	    int result1 = proxy.div(4, 2);
        System.out.println("-->" + result1);
		
		
		
		
		
//		ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
//		ArithmeticCalculator arithmeticCalculator = (ArithmeticCalculator) ctx.getBean("arithmeticCalculator");
//		
//		System.out.println(arithmeticCalculator.getClass().getName());
//		
//		int result = arithmeticCalculator.add(1, 2);
//		System.out.println("result:" + result);
//		
//		result = arithmeticCalculator.div(1000, 10);
//		System.out.println("result:" + result);
	}
	
}

结果：

The methodaddbegins with[1, 2]

The methodaddbegins with3
-->3
The methoddivbegins with[4, 2]

The methoddivbegins with2
-->2