A Login web using Java Servlet and mySQL, problems about connected to MySQL -
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i wrote login web , can't work well. may problem of mysql connecting.
here code. it's simple. there servletlogin.java , index.jsp.
servletlogin.java
package login; import java.io.ioexception; import javax.servlet.servletexception; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; import javax.servlet.http.httpsession; import java.sql.*; public class servletlogin extends httpservlet { private static final long serialversionuid = 1l; private string name; private string pass; public servletlogin() { super(); // todo auto-generated constructor stub } protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { // todo auto-generated method stub dopost(request, response); } protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { // todo auto-generated method stub string printout = ""; this.name = request.getparameter("username"); this.pass = request.getparameter("password"); if (name == "" || name == null || name.length() > 20) { try { printout = "２０字以内ユーザネームを再入力ください"; request.setattribute("message", printout); response.sendredirect("index.jsp"); return; } catch (exception e) { // todo: handle exception e.printstacktrace(); } } if (pass == "" || pass == null || pass.length() > 20) { try { printout = "２０字以内のパスワードを再入力ください"; request.setattribute("message", printout); response.sendredirect("index.jsp"); return; } catch (exception e) { // todo: handle exception e.printstacktrace(); } } // database driver try { class.forname("com.mysql.jdbc.driver"); } catch (exception e) { // todo: handle exception system.out.println("class not found exception"); } // create url string url = "jdbc:mysql://localhost:3306/databasedemo"; try { connection conn = drivermanager.getconnection(url,"root",""); statement stmt = conn.createstatement(); string sql = "select * userinfo username='"+name+"' , password= '"+pass+"'"; resultset rs = stmt.executequery(sql); if (rs.next()) { if (this.name.equals(rs.getstring(1))||this.pass.equals(rs.getstring(2))) { response.sendredirect("success.jsp"); } } } catch (exception e) { // todo: handle exception e.printstacktrace(); } } } index.jsp
<%@ page language="java" contenttype="text/html; charset=utf-8" pageencoding="utf-8"%> <!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=utf-8"> <title>ログイン</title> <script type="text/javascript"> function changeimg() { document.getelementbyid("validatecodeimg").src="${pagecontext.request.contextpath}/checkcodeimage?" + math.random(); } </script> </head> <body> <form action="${pagecontext.request.contextpath}/servletlogin"> <table border="0" align="center"> <tr height="30"></tr> <tr align="center"> <td colspan="2"><font size="20">java web</font></td> </tr> <tr height="30"></tr> <tr height="50"> <td>ユーザネーム</td> <td><input type="text" name="username" placeholder="ユーザネームを入力してください"></td> </tr> <tr height="50"> <td>パスワード</td> <td><input type="password" name="password" placeholder="パスワードを入力してください"></td> </tr> <tr height="50"> <td><img alt="認めない" src="${pagecontext.request.contextpath}/checkcodeimage" id="validatecodeimg" onclick="changeimg()"> </td> <td><input type="text" name="checkcode" placeholder="右側の文字を入力してください"></td> </tr> <tr height="50"> <td colspan="2" align="center"> <input type="submit" name="login" value="ログイン"> </td> </tr> </table> </form> </body> </html> and here database called databasedemo.
+--------+----------+----------+
| userid | username | password |
+--------+----------+----------+
| 1 | jack | 123456 |
| 2 | mary | 654321 |
+--------+----------+----------+
i think stucked command in servletlogin.java. supposed submit form , turn servletlogin.java , command.
if username , password null, recording code in servlet.java, go index.jsp. , went well.
but if username , password same in database, should have go page success.jsp. when run it, shows nothing. seems has not been submitted , command in servletlogin.java. , url shows http://localhost:8080/logindemo/servletlogin?username=jack&password=123456&checkcode=axww&login=%e3%83%ad%e3%82%b0%e3%82%a4%e3%83%b3
i'm confused of it. think have problem connecting mysql. don't know how fix it. please me it...
update
i have solved problem!
when run code, exception shows class not found exception java.sql.sqlexception: no suitable driver found jdbc:mysql://localhost:3306/databasedemo. exception of jdbc driver.
when exception shows, there's 4 reason:
- wrong url. please check right code:
connection conn=drivermanager.getconnection("jdbc:mysql://localhost:3306/xx","root","xxxx" - wrong driver declaration, right 1 :
com.mysql.jdbc.driver - mysql-connector-java-5.1.40.jar must same version mysql.
- mysql-connector-java-5.1.40.jar has been put wrong position. right position copy in web-inf file.
as me, put .jar in wrong position. , when copy in file web-inf, code run well. hope someone. , code above simple webpage of login. continue complete java project.
and answered question. @ravi kumar pointed out 1 of mistakes, , corrected it. it's big mistake of me using mysql.
my best guess query
select * userinfo username='"+name+"' , password= '"+pass+"'" this select 1 | jack | 123456
now rs.getstring(1)=1 ie id , rs.getstring(2) jack ie. username
instead use
rs.getstring("username"); rs.getstring("password"); you may change query
select username,password userinfo username='"+name+"' , password= '"+pass+"'" in order make work existing code
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