Javaweb Small exercise: Find the same username and password in the database

Source: Internet
Author: User

/* Practice Questions:
* Create a person data table in MySQL database, add three fields, Id,user,password, and enter several records
* Exercises: Define a login.html, which defines two request fields: User,password, sending requests to loginservlet.
* Re-create one, Loginservlet (need to inherit from HttpServlet, and override Dopost method)
* The User,password in which the request was obtained
* Use JDBC to query the person table for any records that correspond to the User,password of the page input
* If there is the corresponding hello:xxx, if not, the corresponding sorry:xxx XXX for the user
* */

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First build a table in MySQL with the name of my person, and then take the open source package that connects to the database.


The Web. xml file under LIB is configured as:

<?xml version= "1.0" encoding= "UTF-8"?>
<web-app xmlns:xsi= "" xmlns= "Http://" xsi: schemalocation= "Http://" id= "Webapp_ ID "version=" 2.5 ">

<!--loginservlet Configuration and mapping--
<!--/loginservlet is a form submission method in Login.html-



Form login.html created under WebContent, making the class, configuration file, form connected

<! DOCTYPE html>
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 ">
<title> How to submit the form </title>
<form action= "Loginservlet" method= "POST" >
Username:<input type= "text" name= "username"/>
Password:<input type= "password" name= "password"/>
<input type= "Submit" value= "Submit"/>


LoginServlet1 class:

public class LoginServlet1 extends httpservlet{

HttpServlet: is a Servlet that inherits from Genericservlet. Customized for the HTTP protocol.

Overriding the Dopost method
protected void DoPost (HttpServletRequest req, HttpServletResponse resp)
Throws Servletexception, IOException {
PrintWriter Out=resp.getwriter ();

String Username1=req.getparameter ("username");
String password1=req.getparameter ("password");

String sql= "SELECT count (id) from the person where"
+ "Username=?" and password=? ";
Connection Connection=null;
PreparedStatement Preparedstatement=null;
ResultSet Resultset=null;
try {
Get the file that connects to the database
Class.forName ("Com.mysql.jdbc.Driver");
String url= "Jdbc:mysql:///test";
String username2= "root";
String password2= "lxn123";

Connection=drivermanager.getconnection (URL, username2, password2);
Preparedstatement=connection.preparestatement (SQL);
Preparedstatement.setstring (1, username1);
Preparedstatement.setstring (2, Password1);
Resultset=preparedstatement.executequery ();

if ( ()) {
int Count=resultset.getint (1);
if (count>0) {
Out.println ("Hello:" +username1);
Out.println ("Sorry:" +username1);

} catch (Exception e) {
E.printstacktrace ();
finally {
if (resultset!=null) {
try {
Resultset.close ();
} catch (SQLException e) {
TODO auto-generated Catch block
E.printstacktrace ();
if (preparedstatement!=null) {
try {
Preparedstatement.close ();
} catch (SQLException e) {
TODO auto-generated Catch block
E.printstacktrace ();
if (connection!=null) {
try {
Connection.close ();
} catch (SQLException e) {
TODO auto-generated Catch block
E.printstacktrace ();


Javaweb Small exercise: Find the same username and password in the database

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