java - 从 servlet 到 jsp 的请求调度程序出现问题

Question

我最近开始学习JSP和Servlet。我在使用 requestdispatcher 将 dataList(数据库中的行)转发到 JSP 时遇到问题。事实上，我的 JSP 页面有错误，我无法弄清楚。由于我正在学习，我找不到错误在哪里:

谢谢!

以下是我收到的错误

org.apache.jasper.JasperException: An exception occurred processing JSP page /dataPage.jsp at line 29

26:         %>
27:         <tr>
28:             <td width="100"><%=itr.next()%></td>
29:             <td width="100"><%=itr.next()%></td>
30:             <td width="100"><%=itr.next()%></td>
31:             <td width="100"><%=itr.next()%></td>
32:         </tr>


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:519)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:428)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    AuthenticationServlet.doPost(AuthenticationServlet.java:60)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

我的 JSP 代码是:

<table border="1" width="400">
        <tr>
            <td width="100"><b>Name</b>
            </td>
            <td width="100"><b>Contact No</b>
            </td>
            <td width="100"><b>SSN</b>
            </td>
            <td width="100"><b>Date of Birth</b>
            </td>
        </tr>

        <%  
            List<String> data = (List<String>)request.getAttribute("data");         
            Iterator<String> itr = data.iterator();
            while (itr.hasNext()) {
        %>
        <tr>
            <td width="100"><%=itr.next()%></td>
            <td width="100"><%=itr.next()%></td>
            <td width="100"><%=itr.next()%></td>
            <td width="100"><%=itr.next()%></td>
        </tr>
        <%
            }
        %>
    </table>

我在 servlet 中的代码是

List<String> dataList = new ArrayList<String>();

        try {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection(url);
            conn.createStatement();

            stmt = conn.prepareStatement("SELECT name,password FROM employeeinfo WHERE name=? AND password=?");         
            stmt.setString(1, username);
            stmt.setString(2, password);
            rs = stmt.executeQuery();

            if(rs != null) {
                while(rs.next()) {
                    int i = rs.getRow();
                    if(i == 1) {
                        dataList.add(rs.getString("name"));
                        dataList.add(rs.getString("contactno"));
                        dataList.add(rs.getString("ssn"));
                        dataList.add(rs.getString("dob"));
                    }
                }
            } else {
                out.println("Invalid User !!");
            }

        } catch(Exception e) {
            e.printStackTrace();
        }
        request.setAttribute("data", dataList);
        // Dispatch the request
        RequestDispatcher dispatcher = request.getRequestDispatcher(page);
        if(dispatcher != null) {
            dispatcher.forward(request, response);
        }

Answer 1

您没有在查询中选择 contactno、dob 和 ssn。

将您的查询修改为select name, contactno, dob, ssn from employeeinfo WHERE ...。