JavaWeb学习记录（二十）——Model1模式（javaBean+jsp）实现简单计算器案例

¨JSP技术提供了三个关于JavaBean组件的动作元素，即JSP标签，它们分别为：

¨<jsp:useBean>标签：用于在JSP页面中查找或实例化一个JavaBean组件。

¨<jsp:setProperty>标签：用于在JSP页面中设置一个JavaBean组件的属性。

<jsp:getProperty>标签：用于在JSP页面中获取一个JavaBean组件的属性

一、计算器的实体Bean

package web13.domain;

public class Calculator {
   private double firstNum;
   private double secondNum;
   private String oper;
   private double result;
   public Calculator() {
       super();
       // TODO Auto-generated constructor stub
   }
   public Calculator(double firstNum, double secondNum, String oper,
           double result) {
       super();
       this.firstNum = firstNum;
       this.secondNum = secondNum;
       this.oper = oper;
       this.result = result;
   }
   public double getFirstNum() {
       return firstNum;
   }
   public void setFirstNum(double firstNum) {
       this.firstNum = firstNum;
   }
   public double getSecondNum() {
       return secondNum;
   }
   public void setSecondNum(double secondNum) {
       this.secondNum = secondNum;
   }
   public String getOper() {
       return oper;
   }
   public void setOper(String oper) {
       this.oper = oper;
   }
   public void calculator(){
       if("+".equals(oper)){
           result=firstNum+secondNum;
       }else if("-".equals(oper)){
           result=firstNum-secondNum;
       }else if("*".equals(oper)){
           result=firstNum*secondNum;
       }else if("/".equals(oper)){
           result=firstNum/secondNum;
       }
   }
   public double getResult() {
       calculator();
       return result;
   }
   public void setResult(double result) {
       this.result = result;
   }

}

二、jsp页面（cal.jsp）

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'cal.jsp' starting page</title>

   <meta http-equiv="pragma" content="no-cache">
   <meta http-equiv="cache-control" content="no-cache">
   <meta http-equiv="expires" content="0">
   <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
   <meta http-equiv="description" content="This is my page">
   

</head>

<body>
    <div>
       <jsp:useBean id="c" scope="request" class="web13.domain.Calculator"></jsp:useBean>
       <jsp:setProperty property="firstNum" name="c" param="firstNum"/>
       <jsp:setProperty property="secondNum" name="c" param="secondNum"/>
       <jsp:setProperty property="oper" name="c" param="oper"/>
       <c:if test="${c.oper!=null }">计算结果：
           <jsp:getProperty property="firstNum" name="c"/>
           <jsp:getProperty property="oper" name="c"/>
           <jsp:getProperty property="secondNum" name="c"/>=
           <jsp:getProperty property="result" name="c"/>
       </c:if>
       <form action="./cal.jsp" method="post">
       <table>
           <tr>
               <td colspan="2"></td>
           </tr>
           <tr>
               <td colspan="2">简单计算器</td>
           </tr>
           <tr>
               <td>第一个参数</td>
               <td><input type="text" name="firstNum"/></td>
           </tr>
           <tr>
               <td>操作数</td>
               <td>
                   <select name="oper">
                       <option>+</option>
                       <option>-</option>
                       <option>*</option>
                       <option>/</option>
                   </select>
               </td>
           </tr>
           <tr>
               <td>第二个参数</td>
               <td><input type="text" name="secondNum"/></td>
           </tr>
           <tr>
               <td colspan="2"><input type="submit" value="计算"/></td>
           </tr>
       </table>
       </form>
    </div>
</body>
</html>