今天學習了傳智播客的視頻
http://study.163.com/course/courseLearn.htm?courseId=214022#/learn/video?lessonId=309361&courseId=214022 第111課時，跟着視頻做了一個簡單的網頁計算器。由於是第一次接觸Javabean，有好多地方還不太瞭解，因此寫下此文，方便以後查閱和使用，有什麼不太恰當的描述歡迎指正。
開發環境：Eclipse+Tomcat
首先放上熱騰騰的運行結果圖：
項目的整體結構圖如下圖所示：
web.xml代碼如下：
<?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的代碼如下：
package calculate;
import java.math.BigDecimal;
import javax.management.RuntimeErrorException;
//封裝計算數據的bean
public 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("除數不能爲0！");
}
this.result = first.divide(second,20,BigDecimal.ROUND_HALF_DOWN).toString();
break;
}
default:
throw new RuntimeException("運算符異常");
}
}
}
這部分要注意在最開始的時候要設置firstNum、secondNum和operator的初始值，若是沒有初始值的話運行程序會由於無法獲取到這三個參數而報錯。報錯截圖如下：
calculater.jsp的代碼如下：
<%@ 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>計算器</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/>
計算結果是：
<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">簡單計算器</td>
</tr>
<tr>
<td>第一個參數</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>第二個參數</td>
<td>
<input type="text" name="secondNum">
</td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="計算">
</td>
</tr>
</table>
</form>
</body>
</html>