问向NetBeans项目添加MySQL驱动程序库

EN

Login





Login


     
      Email:
      
    
     
      Salasana

HTTP Status 500 - Internal Server Error

type Exception report

messageInternal Server Error

descriptionThe server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 4.1 logs.

GlassFish Server Open Source Edition 4.1

/*
 * Remember to install a MYSQL driver library
 * or the file will alert
 * NullPointerException.
 */

package Servlets; //the package in which the Servlet is part of.


import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

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

    Connection conn = null;

    /**
     * Initializes the servlet.
     */
    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);

        //Connect to database with database-class
        try {
        conn = Classes.SQL.openConnection();
        }
        catch (Exception e) {
           System.out.println("Cannot connect to database " + e);
        }
    }

    /**
     * Destroys the servlet.
     */
    @Override
    public void destroy() {

    //Closing the database connection
         try {
          conn.close();
        } catch ( SQLException se ) {
           System.out.println("Exception " + se);
        }
    }

    //Everything is done in doPost method.
    //This Servlet does not use doGet() or ProcessRequest()

    /** 
     * Handles the HTTP POST method.
     * @param request servlet request
     * @param response servlet response
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {


    PrintWriter out = response.getWriter();

    /*Unless there is a session, one is created.
        It is used to check if the user has logged in.*/

     HttpSession session = request.getSession(true);

        //Reading the parameters from login form.
        String email = request.getParameter("email");
        String password = request.getParameter("password");

        out.print(email);

        //Created login_ok and set it to false by default.
        boolean login_ok = false;


     try {
     //let's create a Statement with which the sql can be run with.
     Statement stmt = conn.createStatement();

     //Run SQL and save it to ResultSet rs.
     ResultSet rs = stmt.executeQuery("SELECT email, password FROM clients");

     //Go trough the results with while loop and next-method, which returns the value true, until we've reached last result.
     while(rs.next())
     {
       //Reading the data
       String email2 = rs.getString("email");
       String salasana2 = rs.getString("password);

       //If user input has been found from database,
       //login_ok becomes true and looping ends.
       if(email.compareTo(email2) == 0 && password.compareTo(password2) == 0)
       {
           login_ok = true;
           break;
       }

     }


     //If login_ok is true, save info about logging to session and guide the user to Clients.jsp
        if( login_ok == true )
        {
            //session is informed about login
            session.setAttribute("login", "ok");
            //Debugging printed to console.
            System.out.println("Login ok");
            //Proceeding to clients
            response.sendRedirect("clients.jsp");
            //Return stops the servlet run.
            return;
        }
      //Login false -> redirected to login page.
        else {
            response.sendRedirect("login.htm");
        }

    }

     catch(SQLException se){

     out.println("Error: " + se);

     }

        out.close();
    }


}