useBean类属性的值无效

Question

useBean类属性的值无效

我是JSP的新手,并尝试简单的功率计算器.所以我从用户那里得到2个数字,然后我得到计算结果并在页面上显示.这是我的bean类:

package org.mypackage.power;

public class MyPow {

    private double base;
    private double pow;
    private double result;

    MyPow()
    {
        base = 0;
        pow=1;
    }

    /**
     * @return the base
     */
    public double getBase() {
        return base;
    }

    /**
     * @param base the base to set
     */
    public void setBase(double base) {
        this.base = base;
    }

    /**
     * @return the pow
     */
    public double getPow() {
        return pow;
    }

    /**
     * @param pow the pow to set
     */
    public void setPow(double pow) {
        this.pow = pow;
    }


    /**
     * @return the result
     */
    public double getResult() {
       return Math.pow(base, pow);
    }

    /**
     * @param result the result to set
     */
    public void setResult(double result) {
        this.result = result;
    }
}

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这是索引页面:

<HTML>
<BODY>
<FORM METHOD=POST ACTION="result.jsp">
What's your base? <INPUT TYPE=TEXT NAME=base SIZE=20>
What is your power <INPUT TYPE=TEXT NAME=power SIZE=10>

<P><INPUT TYPE=SUBMIT>
</FORM>
</BODY>
</HTML>

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这是将显示结果的JSP页面

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <h1>Hello World!</h1>
        <jsp:useBean id="powerBean" scope="session" class="org.mypackage.power.MyPow" />
        <jsp:setProperty name="powerBean" property="*"/>
        <jsp:getProperty name="powerBean" property="result"/>
    </body>
</html>

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这段代码给出了