PreparedStatement or Connection threw Nullpointer exc

[Jan.dbae]

Hello
I try to find the problem since a few days. i cant find it...
I am shore that my db-Connection usually works (tried another - working - class.)

here the sc:

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends javax.servlet.http.HttpServlet {
/**
* @author Jan
*/
private static final long serialVersionUID = -657338316901350363L;

protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();

// auslesen des Kennworts
String passwort = request.getParameter("passwort");

// auslesen der Kennung
String kennung = request.getParameter("kennung");

//Connection aufbauen
Connection conn = datenbankverbindung.DBConnect.getConnection();

// SQL-Statement definieren
PreparedStatement stmt = null;

String statement = "SELECT benutzername, passwort, admin from benutzer WHERE kennung = ? " +
"and passwort = ? LIMIT 1";
try {
ResultSet rs = null;
stmt = conn.prepareStatement(statement);
rs = stmt.executeQuery();
while(rs.next()) {
String name = rs.getString("vorname") + " " + rs.getString("name");
}
// Resultset instanziieren

//variablen setzen
stmt.setString(1, kennung);
stmt.setString(2, passwort);
} catch (SQLException e2) {
e2.printStackTrace();
}



}}

I get the Connection from the followin class:
package datenbankverbindung;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
* @author Jan
*/
public class DBConnect {

/**
* @return db - connection
*/
public static Connection getConnection() {
Connection conn = null;

String dbname = "postgres";
String nutzer = "postgres";
String server = "localhost:5432";
String passwort = "pw";
String url = "jdbc:postgresql://" + server + "/" + dbname;
try {
Class.forName("org.postgresql.Driver");
conn = DriverManager.getConnection(url, nutzer, passwort);
} catch (ClassNotFoundException exc) {
System.out.println(exc.getMessage());
} catch (SQLException exc) {
System.out.println(exc.getMessage());
}
return conn;
}


}

NPE appears at this line:
"stmt = conn.prepareStatement(statement);"

i hope you can help me...

Jan

[Tolls]

conn is null.
It's the only thing that will throw your NPE on that line (as statement is clearly not null having been declared with the SQL string).
I would guess that you are getting another exception, in the getConnection code. That should really be throwing those exceptions, because a failure to connect means you really don't want to be continuing with your code.

[Jan.dbae]

19.08.2011 02:06:24 org.apache.catalina.core.AprLifecycleListener init
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Program Files\Java\jre6\bin;C:\Windows\Sun\Java\bin;C:\Win dows\system32;C:\Windows;C:\Windows\system32;C:\Wi ndows;C:\Windows\System32\Wbem;C:\Windows\System32 \WindowsPowerShell\v1.0\;C:\Program Files (x86)\ATI Technologies\ATI.ACE\Core-Static;.
19.08.2011 02:06:24 org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNUNG: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:test' did not find a matching property.
19.08.2011 02:06:24 org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNUNG: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Trikotwebshop' did not find a matching property.
19.08.2011 02:06:24 org.apache.tomcat.util.digester.SetPropertiesRule begin
WARNUNG: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:Trikotwelt' did not find a matching property.
19.08.2011 02:06:25 org.apache.coyote.http11.Http11Protocol init
INFO: Initializing Coyote HTTP/1.1 on http-8080
19.08.2011 02:06:25 org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 1506 ms
19.08.2011 02:06:25 org.apache.catalina.core.StandardService start
INFO: Starting service Catalina
19.08.2011 02:06:25 org.apache.catalina.core.StandardEngine start
INFO: Starting Servlet Engine: Apache Tomcat/6.0.32
19.08.2011 02:06:26 org.apache.coyote.http11.Http11Protocol start
INFO: Starting Coyote HTTP/1.1 on http-8080
19.08.2011 02:06:26 org.apache.jk.common.ChannelSocket init
INFO: JK: ajp13 listening on /0.0.0.0:8009
19.08.2011 02:06:26 org.apache.jk.server.JkMain start
INFO: Jk running ID=0 time=0/47 config=null
19.08.2011 02:06:26 org.apache.catalina.startup.Catalina start
INFO: Server startup in 1106 ms
org.postgresql.Driver
19.08.2011 02:07:08 org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet LoginServlet threw exception
java.lang.NullPointerException
at LoginServlet.doPost(LoginServlet.java:43)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:717)
at org.apache.catalina.core.ApplicationFilterChain.in ternalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.do Filter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invo ke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invo ke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke( StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invok e(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.servic e(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(H ttp11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11Conn ectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run( JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)


i have a working class that do what i want but i would/have to outsource the connection method...
also when i copy exactly the same code from this class it failed

[Tolls]

"org.postgresql.Driver"
You are getting that line because that is the result of e.getMessage().
Which is why I suggested at the minimum using e.printStackTrace(), but even better throw those exceptions, don't catch them.

[Jan.dbae]

ah thank you.. i thought it just tells me that the driver has been loaded.
it works now.
The .class file in sourse-folder was wrong.. dont know why. perhaps eclipse builds the project incorectly.
thank you.