运行servlet代码时未知的数据库

unknown database while running servlet code

本文关键字：数据库 未知 servlet 代码 运行      更新时间：2023-09-26

我正在尝试简单的servlet和数据库连接程序，但在运行代码并填写表格并提交后，我一直面临数据库连接问题，我得到未知的数据库问题。我已经在很多网站上寻找合理的解决方案，但都没有找到。

看一下servlet代码，即RegisterServlet.java page 

package com.jwt.servlet;
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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

 public class RegisterServlet extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    String n = request.getParameter("userName");
    String p = request.getParameter("password");
    String e = request.getParameter("email");
    String c = request.getParameter("language");
 try{
 System.out.println("connecting...");
        Class.forName("com.mysql.jdbc.Driver");
        System.out.println("connecting to physical database...");
        Connection con = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/User1", "root", "root");
        PreparedStatement ps = con.prepareStatement("insert into USERDETAILS values(?,?,?,?)");
        System.out.println("Connection has been made");
        ps.setString(1, n);
        ps.setString(2, p);
        ps.setString(3, e);
        ps.setString(4, c);
        int i = ps.executeUpdate();
        if (i > 0)
            out.print("You are successfully registered...");
    } catch (Exception e2) {
        System.out.println(e2);
    }

    out.close();
}
}

register.jsp页面

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
  pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"                                                      "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<script>
function validateForm() {
var x = document.forms["myForm"]["userName"].value;
var y = document.forms["myForm"]["password"].value;
var z = document.forms["myForm"]["email"].value;
var checkString = document.myForm.userName.value;

if ((x == null || x == "") || (y==null || y=="") || (z==null || z=="" ) )
{
    alert("Enter the mandatory fields");
    return false;
    }
}
</script>
</head>
<body>
<div style="background-color:grey;color:white;padding:25px 75px 25px 50px;          text-align:center; border: 1px solid red; display:inline-block; text-   style:bold">
<form name="myForm" action="register" onsubmit="return validateForm()" method="post">
<p id="tt" style="margin-left"></p>
<script>
 document.getElementById("tt").innerHTML = Date();
</script>
    Name*:<input type="text" name="userName"  placeholder="Enter Name"    style="margin-left:35px; " onkeypress="return alpha(event)" /><br/>
    Password*:<input type="password" name="password" style="margin-     left:12px; margin-top:10px" placeholder="Enter Password" /><br/>
    Email Id*:<input type="text" name="email" placeholder="Enter Email Id" style="margin-left:18px; margin-top:10px" /><br/>
    Language: <select name="language" style="margin-left:80px; margin-top:10px">
      <option>--Select--</option>
        <option>Hindi</option>
        <option>English</option>
        <option>French</option>
    </select> <br/>
    <p id="demo" style="display:none">Saved...</p>
<input type="submit"            onclick="document.getElementById('demo').style.display='block'"  value="Submit"                                       style="margin-left:150px; margin-top:10px"/>
 <footer style="margin-bottom"> By </footer>
</form>
</div>
</body>
</html>

web.xml页面

 <?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"            xmlns="http://java.sun.com/xml/ns/javaee"       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee         http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
  <display-name>ServletDBExample</display-name>
  <servlet>
    <servlet-name>Register</servlet-name>
    <servlet-class>com.jwt.servlet.RegisterServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>Register</servlet-name>
    <url-pattern>/register</url-pattern>
</servlet-mapping>
<welcome-file-list>
    <welcome-file>register.jsp</welcome-file>
</welcome-file-list>
</web-app>

尝试删除用户名&密码或尝试更改为其他用户。它会起作用的。我遇到了同样的错误，它似乎为我工作。

请确认输入的MySql用户名和密码是否正确。User1数据库应该存在于MySql数据库中。不要忘记添加mysql-connector.jar文件。

如果可能的话，请发布您的错误信息

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