使用符合MVC设计模式的自定义框架实现加法计算器

自定义MVC框架的核心是控制器的实现：首先我们来定义Action接口，实现Controller类。编译环境为eclipse。

package com.dh.ch01.framework;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public interface Action {
	String execute(HttpServletRequest request,HttpServletResponse response);
	
}

创建名为Controller的Servlet

public class Controller extends HttpServlet {
	//声明由控制器Controller维护的Action映射，其中保存所有的Action实例
	private HashMap actionMap;
       /**
        * Servlet初始化方法
        */
    public void init() throws ServletException{
    	//初始化actionMap
    	actionMap=new HashMap();
    	//将AddAction对象放入到acctionMap中
    	actionMap.put("add", new AddAction());
//    	actionMap.put("sub", new SubAction());
    }
    private Action determinActionByPath(String path){
    	String actionName=path.substring(path.lastIndexOf('/')+1,path.length()-7);
    	Action ret=(Action)actionMap.get(actionName);
    	return ret;
    }
    
	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//得到path
		String path=request.getServletPath();
		//找出Action
		Action action=(Action)this.determinActionByPath(path);
		//执行操作
		String resultView=action.execute(request, response);
		//控制页面转向
		if(null!=resultView){
			request.getRequestDispatcher(resultView).forward(request, response);
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

web.xml的配置

<servlet-name>Controller</servlet-name>
    <servlet-class>com.dh.ch01.framework.Controller</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Controller</servlet-name>
    <url-pattern>*.action</url-pattern>
  </servlet-mapping>

创建add.jsp页面（用户接收数据）

<title>算数计算器</title>
</head>
<body bgcolor="#ffffc0">

	<h1>算数计算器</h1>
	<form id="calxForm" method="post" action="add.action">
	<table>
		<tbody>
			<tr>
				<td>第一个数</td>
				<td><input type="text" name="num1"/></td>
			</tr>
			<tr>
				<td>第二个数</td>
				<td><input type="text" name="num2"/></td>
			</tr>
			<tr>
				<td><input type="submit" value="加"/></td>
			</tr>
		</tbody>
	</table>
	</form>
</body>

创建Calculator，实现算数运算

public class Calculator {
	public double add(double a,double b){
		return a+b;
	}
	public double subtract(double a,double b){
		return a-b;
	}
	public double multiply(double a,double b){
		return a*b;
	}
	public double divide(double a,double b){
		return a/b;
	}
}

创建AddAction类，实现Action接口

public class AddAction implements Action {
		private Calculator biz=new Calculator();
		public String execute(HttpServletRequest request,HttpServletResponse response){
			//execute获取add.jsp页面的表单数据
			double num1=Double.parseDouble(request.getParameter("num1"));
			double num2=Double.parseDouble(request.getParameter("num2"));
			//调用业务逻辑方法，获得返回值
			double result=biz.add(num1, num2);
			//将结构存放在request中，以便在页面中得到
			request.setAttribute("result", result);
			//返回将要转发到页面路径
			return"add_result.jsp";
		}
		
	
}

创建add_result.jsp页面显示计算结果

<body bgcolor="#ffffc0">
<table>
		<tbody>
			<tr>
				<td>第一个数</td>
				<td>${param.num1}</td>
			</tr>
			<tr>
				<td>第二个数</td>
				<td>${param.num2}</td>
			</tr>
			<tr>
				<td>结果</td>
				<td>${requestScope.result}</td>
			</tr>
		</tbody>
	</table>
	<button onclick="history.go(-1);">返回</button>
</body>

附上两张结构图     

显示如图所示结果就成功啦！同理可以继续完善程序，实现减法，乘法和除法，在这里我就不一一写出啦。