java.lang.NullPointerException at createStatement

[Mario Schwaiger]

Hi!

I am dealing with a Java-Web-Application which works with Hibernate and JDBC (I use BoneCP for the Connection-Pooling) to a MS-SQL-Server 2008.
I use a class to provide the basic-connection (Basicconnection.Java) and a bean to provide some cached values for every session.

As I deploy it it works fine. Can't complain. But after a while an exception is thrown and I'm unable to figure out, why:

Aug 01, 2013 3:00:44 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at datenbankbohnen.Persistenzen.initialisiere(Persistenzen.java:100)
at org.apache.jsp.Partial.Material.Material_jsp._jspService(Material_jsp.java:112)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:722)

public void initialisiere() throws HibernateException {
        Statement stat = null;
        ResultSet rs = null;
        Connection c = null;

        String sql = "SELECT min(prime_number) as mini ,max(prime_number) as maxi FROM matrows";
        try {
            //Hibernate - works fine
            AnnotationConfiguration af = new AnnotationConfiguration();
            SessionFactory factory = af.configure().buildSessionFactory();
            Statistics stats = factory.getStatistics();
            stats.setStatisticsEnabled(true);
            Session session = factory.openSession();
            Transaction tx = session.beginTransaction();
            String hql = "SELECT B FROM material.matrows B order by B.prime_number";
            Query query = session.createQuery(hql);
            material = query.list();
            tx.commit();

//JDBC
            c = Basicconnection.getConnection();
            stat = c.createStatement();

// Mini-Maxi-Part            
            rs = stat.executeQuery(sql);
            if (rs.next()) {
                minb = rs.getInt("mini");
                minb = rs.getInt("maxi");
            }
//            rs.close();


// Groups
            sql = "SELECT GrupID, Grup FROM Groups";
            rs = stat.executeQuery(sql);
            while (rs.next()) {
                gruppen.put(rs.getInt("GrupID"), rs.getString("Grup"));
            }
            Persistenzen.intialized = true;
        } catch (SQLException sqex) {
           /**Messages...*/
        } finally {
            Basicconnection.disconnect(rs, stat, c);
           /**Messages...*/
        }

    }

The error occurs in line 22:

            stat = c.createStatement();

The class Basicconnection looks like this:

public class Basicconnection {

    private static Connection connection = null;
    private static BoneCP connectionPool = null;

    public Basicconnection() {
    }

    public static Connection getConnection() {
        if (connection == null) {
            String password = "secr3t";

                try {
                    Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
                } catch (java.lang.ClassNotFoundException e) {
                    e.printStackTrace();
                    return null;
                }

                try {
                    // setup the connection pool
                    BoneCPConfig config = new BoneCPConfig();
                    config.setJdbcUrl(Info.getConnectionString()); // jdbc:sqlserver://10.1.1.2\\SQLEXPRESS
                    config.setUsername("mario");
                    config.setPassword(password);
                    config.setMinConnectionsPerPartition(5);
                    config.setMaxConnectionsPerPartition(10);
                    config.setPartitionCount(1);
                    connectionPool = new BoneCP(config); // setup the connection pool

                    connection = connectionPool.getConnection(); // fetch a connection

                    if (connection != null) {
                        System.out.println("Connection successful!");
                    } else {
                        System.out.println("Connection failed");
                    }

                    return connection;
                } catch (SQLException e) {
                    e.printStackTrace();
                    if (connection != null) {
                        try {
                            connection.close();
                            return null;
                        } catch (SQLException se) {
                            e.printStackTrace();
                            return null;
                        }
                    }
                    return null;
                }
        } else {
            try {
                if (connection.isClosed()) {
                    return connectionPool.getConnection();
                } else {
                    return connection;
                }
            } catch (SQLException sqle) {
                System.err.println("Fehler: " + sqle.getLocalizedMessage());
                System.err.println("Code: " + sqle.getSQLState());
                return connection;
            }
        }
    }

    public static void disconnect(ResultSet resultSet, Statement statement, Connection connection) {
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
            } // nothing we can do
        }
        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
            } // nothing we can do
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
            } // nothing we can do
        }
    }

What am I doing wrong? Could it be a connection timeout? As said, during the first ~10 Minutes everything goes as expected. And then just Null pointers and I'm unable to make it work any more...
Thank you in anticipation!!

[Jeanne Boyarsky]

That code looks like it returns null if it can't get a connection after printing a log message. Is there anything in the logs before the null pointer?