JSP内置标签-JavaBean标签疑问 - 黑马程序员技术交流社区

JSP代碼：
<div class="blockcode"><blockquote><%@ page language="java" import="java.util.*" pageEncoding="utf-8" %>
<%@ page import="cn.zengfansheng.web.calculator.Calculator" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
</head>
<%--
JSP计算器
--%>
<body>
<%-- C --%>
<%-- 1.将取得的值存入JavaBean --%>
<jsp:useBean id="calculator" class="cn.zengfansheng.web.calculator.Calculator" scope="page" />
<%-- 将地址栏中的参数存入JavaBean --%>
<jsp:setProperty property="*" name="calculator" />
<!-- <jsp:setProperty property="firstNum" name="calculator" param="firstNum"/>
<jsp:setProperty property="operator" name="calculator" param="operator" />
<jsp:setProperty property="secondNum" name="calculator" param="secondNum" /> -->
<%--2.处理计算结果--%>
<%
calculator.operate();
%>
计算结果是：
<jsp:getProperty property="firstNum" name="calculator"/>
<jsp:getProperty property="operator" name="calculator"/>
<jsp:getProperty property="secondNum" name="calculator"/>=
<jsp:getProperty property="result" name="calculator" />
<%-- V --%>
<hr />
<form action="/myday10/calculator/calculator.jsp" method="get">
<table border="1px" align="center">
<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="+" selected>+</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 align="center">
<input type="submit" value="计算" />
</td>
</tr>
</table>
</form>
</body>
</html>

复制代码

package cn.zengfansheng.web.calculator;
import java.math.BigDecimal;
// M
public class Calculator {
double firstNum ;
double secondNum ;
char operator;
double result;
public Calculator(){
System.out.println("构造函数开始了");
}
public double getFirstNum() {
System.out.println("getFirstNum success");
return firstNum;
}
public void setFirstNum(double firstNum) {
this.firstNum = firstNum;
System.out.println("setFirstNum success");
}
public double getSecondNum() {
System.out.println("getSecondNum success");
return secondNum;
}
public void setSecondNum(double secondNum) {
this.secondNum = secondNum;
System.out.println("setSecondNum success");
}
public char getOperator() {
System.out.println("getOperator success");
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
System.out.println("setOperator success");
}
//结果保留小数点后一位
public double getResult() {
System.out.println("getResult success");
BigDecimal bd = new BigDecimal(this.result).setScale(2,BigDecimal.ROUND_HALF_UP);
return bd.doubleValue();
}
public void setResult(double result) {
this.result = result;
System.out.println("setResult success");
}
public void operate(){
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 '/': this.result = this.firstNum/this.secondNum;break;
}
System.out.println("operate success");
}
}

复制代码

构造函数开始了
setOperator success
setFirstNum success
setSecondNum success
setFirstNum success
setOperator success
setSecondNum success
operate success
getFirstNum success
getOperator success
getSecondNum success
getResult success

复制代码

<jsp:setProperty property="firstNum" name="calculator" param="first"/>
<jsp:setProperty property="operator" name="calculator" param="ope" />
<jsp:setProperty property="secondNum" name="calculator" param="second" />

复制代码

<tr>
<td>第一个参数：</td>
<td><input type="text" name="first" /></td>
</tr>
<tr>
<td>运算符：</td>
<td><select name="ope">
<option value="+" selected>+</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="second" /></td>
</tr>

复制代码