Question

Form.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Form</title>
<body bgcolor="#FFFFFF" text="#000000">

<h1>Please enter your details</h1>

<form name="RegistrationForm" action="NewUser" method="post">
    <table cellspacing="5" cellpadding="5" border="1">
        <tr>
            <td align="right">First Name:</td>
            <td><input type="text" name="NewFirstName"></td>
        </tr>
        <tr>
            <td align="right">Last Name:</td>
            <td><input type="text" name="NewLastName"></td>
        </tr>
        <tr>
            <td align="right">Email Address:</td>
            <td><input type="text" name="EmailAddress"></td>
        </tr>
        <tr>
            <td align="right">Phone Number:</td>
            <td><input type="text" name="Phone Number"></td>
        </tr>
        <tr>
            <td align="right">Semester</td>
            <td><input type="text" name="Semester"></td>
        </tr>

    </table>
    <input type="submit" value="Submit">
</form>

</body>
</html>

NewUser.java（Servlet类）

package com.seria.quiz;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class NewUser
 */
@WebServlet("/NewUser")
public class NewUser extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public NewUser() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter pw = response.getWriter();
        Connection conn = null;

        try {
            String FirstName = request.getParameter("firstName");
            System.out.println("Your firstname: " + FirstName);
            String LastName = request.getParameter("lastName");
            System.out.println("Your LastName: " + LastName);
            String Emailid = request.getParameter("email");
            String PhoneNumber = request.getParameter("phoneNumber");
            String Semester = request.getParameter("semester");

            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/seriaquiz", "root", "root");
            PreparedStatement pst = (PreparedStatement) conn
                    .prepareStatement("insert into formdetails(firstName,lastName,email,phoneNumber,semester) values(?,?,?,?,?)");// try2
                                                                                                                                    // the
                                                                                                                                    // name
            pst.setString(1, FirstName);
            System.out.println("Your firstname1: " + FirstName);
            pst.setString(2, LastName);
            System.out.println("Your LastName1: " + LastName);
            pst.setString(3, Emailid);
            pst.setString(4, PhoneNumber);
            pst.setString(5, Semester);

            int i = pst.executeUpdate();
            String msg = " ";
            if (i != 0) {
                msg = "Record has been inserted";
                pw.println("<font size='6' color=blue>" + msg + "</font>");

            } else {
                msg = "failed to insert the data";
                pw.println("<font size='6' color=blue>" + msg + "</font>");
            }
            pst.close();
        } catch (Exception e) {
            pw.println(e);
        }

    }

}

正如标题所说，request.getParameter每次都返回null。我在requestParameter之后放了sysout语句，它显示了null值。任何帮助将不胜感激。很抱歉给您带来不便，我是新来的。

Answer 1

servlet中的参数名称需要在JSP中匹配它们

所以

String FirstName = request.getParameter("firstName");

应该是

String FirstName = request.getParameter("NewFirstName");

Answer 2

你要求错误的参数你应该总是询问你的html

中描述的相同的id / name

request.getParameter("NewFirstName");

Answer 3

来自w3.org部分 17.2控件

用户通过命名控件与表单进行交互。

控件的名称＆＃34;控制名称＆＃34;由名称属性提供。一个
的name属性的范围   FORM元素中的控件是FORM元素。

当提交表单进行处理时，某些控件的名称与其当前的
配对   价值和这些对与表格一起提交。

控制的例子是你的

<input type="text" name="NewFirstName">

因此，当提交表单时，它包含控件名称=值，例如

NewFirstName=YourFirstName

在JSP中，您应该使用控件名称

访问它

String FirstName = request.getParameter("NewFirstName");

参考：http://www.w3.org/TR/html401/interact/forms.html

Answer 4

获取表单参数的确切值，试试这个......

String FirstName = request.getParameter（“NewFirstName”）;

因为..

通过'NewFirstName'指定name属性...

request.getParameter在JSP中返回null

4 个答案: