Question

我正在制作一个具有两个值的应用程序，它返回许多不同的函数答案（加法，减法，div，乘法等）。它是用JSP制作的，我有一个索引和一个错误的JSP。当我尝试在启用了error.jsp的情况下运行该应用程序时，无论我尝试执行什么操作，它总是返回该页面，因为我的代码有问题，但是我不知道是什么。该应用程序还有一个质数部分，您可以在其中输入数字，按ok，如果该数字是质数，则什么都不会发生，但是如果不是，则会出现错误消息。下一个素数和上一个素数只返回您输入的数字中的下一个和上一个素数。

index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page errorPage="error.jsp"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Home Page</title>
    </head>
    <body>
        <h1>Calculations using JSP pages</h1>
        <jsp:useBean id="math" scope="session" class="beans.MathBean" />
        <jsp:useBean id="primenumber" scope="session" class="beans.PrimeBean" />
        <jsp:setProperty name="math" property="*" />
        <jsp:setProperty name="primenumber" property="prime" />
        <form name="form1" method="post">
            <table>
                <tr>
                    <td>Number 1: </td>
                    <td><input type="text" name="numberA" value="${math.numbera}" style="width: 130px"</td>
                </tr>
                <tr>
                    <td>Number 2: </td>
                    <td><input type="text" name="numberB" value="${math.numberb}" style="width: 130px"</td>
                </tr>
                <tr>
                    <td colspan="2" style="text-align: right"><input type="submit" value="OK"</td>
                </tr>
            </table>
        </form>
        <table>
            <tr>
                <td>Add</td><td>${math.add()}</td>
            </tr>
            <tr>
                <td>Subtract</td><td>${math.subtract()}</td>
            </tr>
            <tr>
                <td>Multiply</td><td>${math.multiply()}</td>
            </tr>
            <tr>
                <td>Divide</td><td>${math.divide()}</td>
            </tr>
        </table>
        <form name="form2" method="post">
            <input type="text" name="prime" value="${primenumber.prime}"/> &nbsp;&nbsp;
            <input type="submit" value="OK"/>
        </form>
        <p><a href="Primes?number=next">Next Prime</a>
        <p><a href="Primes?number=previous">Previous Prime</a>
    </body>
</html>

Error.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page isErrorPage="true"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Error page</title>
    </head>
    <body>
        <h1>Error!</h1>
        <p><a href="index.jsp">back 2 menu</a></p>
    </body>
</html>

web.xml文件只是默认设置，其中添加了welcome-file-list，其中包含index.jsp的welcome-file。

MathBean：

package beans;
import java.io.Serializable;

public class MathBean implements Serializable{
    
    private long numbera, numberb;

    public MathBean(long numbera, long numberb) {
        this.numbera = numbera;
        this.numberb = numberb;
    }

    public long getNumbera() {
        return numbera;
    }

    public void setNumbera(long numbera) {
        this.numbera = numbera;
    }

    public long getNumberb() {
        return numberb;
    }
    public void setNumberb(long numberb) {
        this.numberb = numberb;
    }
    public long add() {
        return numbera + numberb;
    }
    public long subtract() {
        return numbera - numberb;
    }
    public long divide() {
        if (numberb == 0) {
            return 0;
        }
        return numbera / numberb; 
    }
    public long multiply() {
        return numbera * numberb;
    }
    
}

PrimeBean：


package beans;

public class PrimeBean {
    private static final long max = 9223372036854775783L;
    private long prime = 2;
    
    public PrimeBean() {
        
    }

    public long getPrime() {
        return prime;
    }

    public void setPrime(long p) throws Exception {
        if(!isPrime(p)) throw new Exception("Illegal number");
        prime = p;
    }
    private static boolean isPrime(long p) {
        if (p == 2 || p == 3 || p == 5 || p == 7) return true;
        if(p<11||p%2 == 0 ) return false;
        for(long t = 3, m = (long)Math.sqrt(p) + 1; t <= m; t+=2) if(p % t == 0) return false;
        return true;
    } 
   public boolean next() {
       if (prime < max) {
           if (prime == 2) prime = 3;
           else for(prime += 2; !isPrime(prime); prime += 2);
           return true;
       }
       return false;
   }
   public boolean previous() {
       if (prime > 2) {
           if(prime == 3) prime = 2;
           else for(prime -= 2; !isPrime(prime); prime -= 2);
           return true;
       }
       return false;
   }
    
}

PrimeServlet：


package servlets;

import beans.PrimeBean;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet(name = "Primes", urlPatterns = {"/Primes"})
public class PrimeServlet extends HttpServlet {


    protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws IOException{
         PrimeBean bean = (PrimeBean) request.getSession().getAttribute("primenumber");
         String number = request.getParameter("number");
         if (number.equals("next")) bean.next(); else bean.previous();
         response.sendRedirect("index.jsp");
        }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

很抱歉张贴所有代码，但是我真的迷路了，我不明白为什么它不起作用。感谢所有帮助。

谢谢！

Answer 1

实施中至少存在两个问题：

Bean必须具有带有 no 参数的公共默认构造函数：

public MathBean() { ...

你有

public MathBean(long numbera, long numberb) { ...

numberA上的HTML输入标签numberB，submit和index.jsp缺少结尾>。

如何修复HTTP状态500索引错误？

1 个答案: