calculate.jsp 源代码如下
<%@ page contentType="text/html;charset=GB2312"%>
<jsp:useBean id="calculator" scope="request" class="ch06.SimpleCalculator">
<jsp:setProperty name="calculator" property="*"/>
</jsp:useBean>
<html>
<head>
<title>简单计算器</title>
<meta http-equiv="Content-Type" content="text/html; charset=GB2312">
</head>
<body>
<p align=center><b>简单计算器</b>
<hr>
计算结果：
<%
try
{
calculator.calculate();
out.println(calculator.getFirst()+calculator.getOperator()+calculator.getSecond()+"="+calculator.getResult());
}
catch(Exception e)
{
out.println(e.getMessage());
}
%>
<hr>
<form action="calculate.jsp" method=get>
<table width="75%">
<tr>
<td align=right>第一个参数</td>
<td><input type=text name="first"></td>
</tr>
<tr>
<td align=right>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 align=right>第二个参数</td>
<td><input type=text name="second"></td>
</tr>
<tr>
<td></td>
<td><input type=submit value=计算></td>
</tr>
</table>
</form>
</body>
</html>
SimpleCalculator.java 源代码如下
package ch06;
public class SimpleCalculator
{
private String first;
private String second;
private double result;
private String operator;
public void setFirst(String first){
this.first=first;
}
public void setSecond(String second){
this.second=second;
}
public void setOperator(String operator){
this.operator=operator;
}
public String getFirst(){
return this.first;
}
public String getSecond(){
return this.second;
}
public String getOperator(){
return this.operator;
}
public double getResult(){
return this.result;
}
public void calculate(){
double one=Double.parseDouble(first);
double two=Double.parseDouble(second);
try{
if(operator.equals("+")) result=one+two;
else if(operator.equals("-")) result=one-two;
else if(operator.equals("*")) result=one*two;
else if(operator.equals("/")) result=one/two;
}
catch(Exception e){
System.out.println(e);
}
}
}
用浏览器浏览产生错误如下
HTTP Status 500 -
--------------------------------------------------------------------------------
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: /myweb/calculate.jsp(2,0) The value for the useBean class attribute ch06.SimpleCalculator is invalid.
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:405)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:146)
org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1223)
org.apache.jasper.compiler.Node$UseBean.accept(Node.java:1116)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2213)
org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2219)
org.apache.jasper.compiler.Node$Root.accept(Node.java:456)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Generator.generate(Generator.java:3284)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:189)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:267)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:255)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:563)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:293)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.
--------------------------------------------------------------------------------
Apache Tomcat/5.5.12
小弟初次学习，求高人指点
[ 此贴被haoran在2007-10-16 11:33重新编辑 ]
