JSP页面实现简单的计算器(JSP+JavaBean适合简单页面显示)

1,CalculatorBean.java的实现封装数据和操作符.

import java.math.BigDecimal;

public class CalculatorBean {

    private double firstNum;
    private double secondNum;
    private char operator = '+'; // int char byte short
    private double 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 char getOperator() {
        return operator;
    }

    public void setOperator(char operator) {
        this.operator = operator;
    }

    public double getResult() {
        return result;
    }

    public void setResult(double result) {
        this.result = result;
    }

    public void calculate() {

        switch (this.operator) {
        case '+': {
            this.result = this.firstNum + this.secondNum;
            break;
        }

        case '-': {
            this.result = this.firstNum - this.secondNum;
            break;
        }
        case '*': {
            this.result = this.firstNum * this.secondNum;
            break;
        }
        case '/': {
            if (this.secondNum == 0) {
                throw new RuntimeException("被除数不能为0!!!");
            }

            this.result = this.firstNum / this.secondNum;

            // 四舍五入
            this.result = new BigDecimal(this.result).setScale(2,
                    BigDecimal.ROUND_HALF_UP).doubleValue();

            break;
        }

        default:
            throw new RuntimeException("对不起，传入的运算符非法！！");
        }

    }

}

2,JSP显示层

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
    <head>
        <title>计算器</title>
    </head>

    <body style="text-align: center;">

        <jsp:useBean id="CalculatorBean" class="cn.itcast.CalculatorBean"></jsp:useBean>
        <jsp:setProperty name="CalculatorBean" property="*" />
        <%
            CalculatorBean.calculate();
        %>

        <br />
        <hr>
        <br />

        计算结果是：
        <jsp:getProperty name="CalculatorBean" property="firstNum" />
        <jsp:getProperty name="CalculatorBean" property="operator" />
        <jsp:getProperty name="CalculatorBean" property="secondNum" />
        =
        <jsp:getProperty name="CalculatorBean" property="result" />


        <br />
        <hr>
        <br />

        <form action="/day09/calculator.jsp" method="post">
            <table border="1" width="50%">
                <tr>
                    <td colspan="2">
                        简单的计算器
                    </td>
                </tr>

                <tr>
                    <td>
                        第一个参数
                    </td>
                    <td>
                        <input type="text" name="firstNum">
                    </td>
                </tr>

                <tr>
                    <td>
                        运算符
                    </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>

效果图