Spring之使用AOP缘由(1-原始实现)

 

为什么要使用AOP呢？我们可以通过下面的一个小需求来找到答案。

 

需求1-日志：在程序执行期间追踪正在发生的活动

需求2-验证：希望计算器只能处理正数的运算

 

代码实现一

 

package xyz.huning.spring4.aop.calculator;

public interface ICalculator {

	double add(double x,double y);
	
	double sub(double x,double y);
	
	double mul(double x,double y);
	
	double div(double x,double y);	
	
}

  

 

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package xyz.huning.spring4.aop.calculator.originimpl;

import java.util.Arrays;

import xyz.huning.spring4.aop.calculator.ICalculator;

public class OriginCalculator implements ICalculator {

	@Override
	public double add(double x, double y) {
		validate(x,y);
		System.out.println("before: " + "[x=" + x + ", y=" + y + "]");
		System.out.println("execute method add ...");
		double result = x + y;
		System.out.println("after: " + "[x=" + x + ", y=" + y + "]");
		return result;
	}

	@Override
	public double sub(double x, double y) {
		validate(x,y);
		System.out.println("before: " + "[x=" + x + ", y=" + y + "]");
		System.out.println("execute method sub ...");
		double result = x - y;
		System.out.println("after: " + "[x=" + x + ", y=" + y + "]");
		return result;
	}

	@Override
	public double mul(double x, double y) {
		validate(x,y);
		System.out.println("before: " + "[x=" + x + ", y=" + y + "]");
		System.out.println("execute method mul ...");
		double result = x * y;
		System.out.println("after: " + "[x=" + x + ", y=" + y + "]");
		return result;
	}

	@Override
	public double div(double x, double y) {
		validate(x,y);
		System.out.println("before: " + "[x=" + x + ", y=" + y + "]");
		System.out.println("execute method div ...");
		double result = x / y;
		System.out.println("after: " + "[x=" + x + ", y=" + y + "]");
		return result;
	}

	private void validate(double x, double y)
	{
		System.out.println("validate parameter: " + Arrays.toString(new double[]{x,y}));
	}
}

 

 

package xyz.huning.spring4.aop.calculator.originimpl;

public class Main {

	public static void main(String[] args) {
		
		OriginCalculator oc1 = new OriginCalculator();
		oc1.add(10, 20);
		oc1.sub(30, 10);
		oc1.mul(10, 10);
		oc1.div(20, 10);
	}
}

 

问题

 

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。