Problem in my login page

[Sarra Sakka]

Hello,
I have created a authentication servlet as follows :

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		/* Connexion � la base de donn�es */
		
		try {
			 Class.forName("org.postgresql.Driver");
		      System.out.println("Driver O.K.");

		      String url = "jdbc:postgresql://localhost:5432/Login";
		      String user = "postgres";
		      String passwd = "DataBase";

		      Connection connexion = DriverManager.getConnection(url, user, passwd);
		      System.out.println("Connexion effective !"); 
		    /* Cr�ation de l'objet g�rant les requ�tes */
			     Statement statement  = connexion.createStatement();
		    /* Ici, nous placerons nos requ�tes vers la BDD */
		    String id = request.getParameter("id").trim();
		    String password = request.getParameter("pass");
		    
		    
		    /* Ex�cution d'une requ�te de lecture */
		    ResultSet resultat = statement.executeQuery( "SELECT user_id,user_password,user_role from users ");
		    /* R�cup�ration des donn�es du r�sultat de la requ�te de lecture */
		   
		    while ( resultat.next() ) { 
		        String iddb = resultat.getString( "user_id" );
		        String passdb = resultat.getString( "user_password" );
		        String roledb = resultat.getString( "user_role" );
		        /* Traiter ici les valeurs r�cup�r�es. */
		        if ((iddb.equals(id))&&(passdb.equals(password))) //there's the same id in data base, so we should check the role
		        {
		        	if(roledb.equals("admin"))//if the role is admin we should verify the password
		        	{
		        		response.sendRedirect("/home.jsp");

		        	}
		        	else if (roledb.equals("employee"))
		        	{
		        		response.sendRedirect("/login_ban.jsp");
		        	}
		        }
		        else //check your data : id_user not found in database
		        {
		        	response.sendRedirect("/login_failure.jsp");;
		        	
		        }
		    }

		} catch ( SQLException e ) {
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 

	}

when, i use it, an exception appears in my console as follows :

java.lang.IllegalStateException: Impossible d''appeler "sendRedirect()" après que la réponse ait été envoyée
	at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:483)
	at com.pack.servlet.Authentication.doPost(Authentication.java:86)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:409)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1044)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2441)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2430)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

I just want to know how can i move to another jsp page from my servlet.
Could you please tell me what's wrong in my code? and why i can't go to another page?
thank you in advance

[Sarra Sakka]

If my query return not only one line but also many line.
How can i retrive it in my servlet ?

[Ulf Dittmer]

You should exit the loop (or put a return statements) after issuing a sendRedirect call.

If my query return not only one line but also many line. How can i retrive it in my servlet ?

That's what the while loop would do, if not every single path through it contained a sendRedirect call.

I think I told you this before, but empty catch blocks are bad - REALLY bad for I/O like DB accesses.