网页计算器的简单实现--jsp开发模式

来源：互联网发布：照片制作软件免费下载编辑：程序博客网时间：2024/05/18 11:46

今天学习了传智播客的视频
http://study.163.com/course/courseLearn.htm?courseId=214022#/learn/video?lessonId=309361&courseId=214022 第111课时，跟着视频做了一个简单的网页计算器。由于是第一次接触Javabean，有好多地方还不太了解，因此写下此文，方便以后查阅和使用，有什么不太恰当的描述欢迎指正。

开发环境：Eclipse+Tomcat

首先放上热腾腾的运行结果图：

项目的整体结构图如下图所示：

项目结构图

web.xml代码如下：

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>calculate</display-name>  <welcome-file-list>    <welcome-file>calculater.jsp</welcome-file>  </welcome-file-list></web-app>

CalculatorBean.java的代码如下：

package calculate;import java.math.BigDecimal;import javax.management.RuntimeErrorException;//封装计算数据的beanpublic class CalculatorBean {    private String firstNum = "0";    private String secondNum = "0";    private char operator = '+';    public String getResult() {        return result;    }    public void setResult(String result) {        this.result = result;    }    private String result;    public String getFirstNum() {        return firstNum;    }    public String getSecondNum() {        return secondNum;    }    public char getOperator() {        return operator;    }    public void setFirstNum(String firstNum) {        this.firstNum = firstNum;    }    public void setSecondNum(String secondNum) {        this.secondNum = secondNum;    }    public void setOperator(char operator) {        this.operator = operator;    }    public void calculate(){        BigDecimal first = new BigDecimal(this.firstNum);        BigDecimal second = new BigDecimal(this.secondNum);        switch (this.operator) {        case '+':            this.result = first.add(second).toString();            break;        case '-':            this.result = first.subtract(second).toString();            break;        case '*':            this.result = first.multiply(second).toString();            break;        case '/':{            if(second.doubleValue()==0){                throw new RuntimeException("除数不能为0！");            }            this.result = first.divide(second,20,BigDecimal.ROUND_HALF_DOWN).toString();            break;        }        default:            throw new RuntimeException("运算符异常");        }    }}

这部分要注意在最开始的时候要设置firstNum、secondNum和operator的初始值，若是没有初始值的话运行程序会由于无法获取到这三个参数而报错。报错截图如下：

未初始化参数报错

calculater.jsp的代码如下：

<%@ page language="java" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head>    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">    <title>计算器</title></head><body style="text-align: center;">    <jsp:useBean id="calculatorBean" class="calculate.CalculatorBean"></jsp:useBean>    <jsp:setProperty property="*" name="calculatorBean"/>    <%         try{            calculatorBean.calculate();        }catch(Exception e){            out.write(e.getMessage());        }    %>    <br/>--------------------------------------------------<br/>    计算结果是：    <jsp:getProperty property="firstNum" name="calculatorBean"/>    <jsp:getProperty property="operator" name="calculatorBean"/>    <jsp:getProperty property="secondNum" name="calculatorBean"/>    =    <jsp:getProperty property="result" name="calculatorBean"/>    <br/>--------------------------------------------------<br/>    <br/>    <form action="/calculate/calculater.jsp" method="post">    <table border="1" align="center">    <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>操作符</td>        <td>            <select name="operator">                <option value="+">+</option>                <option value="-">-</option>                <option value="*">*</option>                <option value="/">/</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></body></html>

0 0