servlet部署到服务器上运行的时候，在网页里一直显示failed，下面是代码

package com.login;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;

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

/**

• Servlet implementation class LoginServlet
  */
  public class LoginServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  /**

  • @see HttpServlet#HttpServlet() */ public LoginServlet() { 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
    Connection conn;
    PreparedStatement sql;
    ResultSet rs;
    try
    {
    Class.forName("com.mysql.jdbc.Driver");
    }
    catch (Exception e)
    {
    System.out.print(e);
    }
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    response.setContentType("text/html");
    response.setCharacterEncoding("utf-8");
    PrintWriter out = response.getWriter();
    String msg = null;
    String uri="jdbc:mysql://localhost:3306/monitordb?"+"user=root&password=123456";
    String selectsql = "select username,password from user where username=? and password=?";

    if(username!=null&&password!=null)
    {
    msg = "success";

    try
    {
    //String url = "jdbc:mysql://localhost:8080/monitordb";
    String insertSql = "insert into user values(?,?)";
    conn = DriverManager.getConnection(uri);
    sql = conn.prepareStatement(insertSql);
    sql.setString(1,username);
    sql.setString(2,password);
    int status = sql.executeUpdate();
    if(status!=0)
    {
    System.out.print("添加数据成功！");
    }else
    {
    System.out.print("添加数据失败");
    }
    conn.close();
    }
    catch (SQLException e)
    {
    System.out.print(e);
    }
    }else
    {
    msg = "failed";
    }
    out.print(msg);
    out.flush();
    out.close();
    }

  /**

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

  }

}

也许是你的用户名和密码根本就没有从数据库获取到；
PreparedStatement sql;我感觉有问题
我是这样做的PreparedStatement sql=null;

一般像连接数据库这样的，你可以放在init里面进行初始化，关于问题就是failed应该是有后台日志的。