TOMCAT 与javabean问题

大家帮我看看:这是SimpleCalculator.java代码,编译后生成SimpleCalculator.class,考到"C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps\myapp\WEB-INF\classes\bean"目录下.
package bean;
public class SimpleCalculator {
private String first;
private String second;
private double result;
private String operator;
public String getFirst() {
return first;
}
public void setFirst(String first) {
this.first = first;
}
public String getOperator() {
return operator;
}
public void setOperator(String operator) {
this.operator = operator;
}
public String getSecond() {
return second;
}
public void setSecond(String second) {
this.second = second;
}
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);
}

}
}
调用上面bean的JSP页面部分代码如下:该文件在"C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps\myapp"目录下.
<body>
<p>&nbsp;</p>
<hr />
计算结果:
<jsp:useBean id="calculator" scope="request" class="bean.SimpleCalculator">
<jsp:setProperty name="calculator" property="*"/>
</jsp:useBean>
<%
calculator.calculate();
out.println(calculator.getFirst()+calculator.getOperator()+calculator.getSecond()+"="+calculator.getResult());
%>
<hr /><form id="form1" name="form1" method="post" action="calculate.jsp">
  <table width="353" border="1" align="center">
    <tr>
      <td>第一个操作数</td>
      <td><label>
        <input type="text" name="first" />
      </label></td>
    </tr>
    <tr>
      <td>操作符号</td>
      <td><label>
        <select name="operator" id="operator">
          <option value="+">+</option>
          <option value="-">-</option>
          <option value="*">*</option>
          <option value="/">/</option>
        </select>
      </label></td>
    </tr>
    <tr>
      <td>第二个操作数</td>
      <td><input name="second" type="text" id="second" /></td>
    </tr>
    <tr>
      <td colspan="2" align="center"><label>
        <input type="submit" name="Submit" value="计算" />
      </label></td>
    </tr>
  </table>
</form>
在IE地址栏输入:http://localhost:8088/myapp/calculate.jsp
提示下列错误信息:
org.apache.jasper.JasperException: An exception occurred processing JSP page /calculate.jsp at line 1815: <jsp:setProperty name="calculator" property="*"/>
16: </jsp:useBean>
17: <%
18: calculator.calculate();
19: out.println(calculator.getFirst()+calculator.getOperator()+calculator.getSecond()+"="+calculator.getResult());
20: %>
21: <hr />
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:505)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)我整了好久了,但是老是弄不好呀,请大家帮帮忙.