引言

對類(class)增強的手段通常分為以下三類

1.繼承 子類通過繼承父類或者實現接口對類進行增強

2.裝飾者模式(Wrapper) 常用於對類的某個方法進行重寫,以實現更強大的功能.常用於場合緩沖流,Struct2中StructRequestWarpper類 實現準則:是你還有你,一切全靠你

3.動態代理 一句話概括:獲取實現了一組接口的類對象 需提供目標對象,增強建議 三大參數 :ClassLoader Class[] interfaces InvocationHandler (調用目標對象的方法時會調用這)

區別與裝飾者模式:裝飾者模式通常是對一個類進行加強,而動態代理是獲取一組接口的方法在對類進行增強

具體實現

package com.atguigu.spring.aop;

public interface ArithmeticCalculator {

	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 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;
	}

}

　　要對Arithmetic 的add,sub,mul,div方法進行增強,添加日誌方法,用到了代理

傳統的做法

package com.atguigu.spring.aop;

public class ArithmeticCalculatorLoggingImpl implements ArithmeticCalculator {

	@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 ends 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 ends 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 ends 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 ends with " + result);
		return result;
	}

}

　　由以上代碼可以看出,相似重復的代碼太多,要對改類進行重寫成更簡單的類,用到了到動態代理

AOP 面向切面編程詳解