Java.lang.NullPointerException and ConnectionPool problem

Question

refresh page , problem gone
java.lang.NullPointerException
at Deferment.UpdatePostgraduate.getStatus(UpdatePostgraduate.java:278)
at Deferment.UpdatePostgraduate.doPost(UpdatePostgraduate.java:175)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:402)
at org.apache.catalina.servlets.InvokerServlet.doPost(InvokerServlet.java:170)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
UpdatePostgraduate.java:278
->while (rs.next()) {
175-> tarCount=getStatus(userid);
now I have
Connection conn = null;
CallableStatement calstat=null;
ResultSet rs = null;
in every of my function
and my
public Connection getConnection()         throws SQLException, ServletException       {           Connection conn = null;           try{           pool.getConnection();           }catch (SQLException sqle) {             throw new ServletException(sqle.getMessage());         }           return conn;       }

Answer 1

private DataSource pool = null; 
    int tarCount;
    int sendMail;
    @Override
    public void init() throws ServletException {
        Context env = null;
        try {
            env = (Context) new InitialContext().lookup("java:comp/env");
            pool = (DataSource) env.lookup("jdbc/test");
            if (pool == null) {
                throw new ServletException(
                        "'jdbc/test' is an unknown DataSource");            }
        } catch (NamingException ne) {
            throw new ServletException(ne);
      public Connection getConnection()
        throws SQLException, ServletException
          Connection conn = null;
          try{
         conn=pool.getConnection();
          }catch (SQLException sqle) {
            System.out.println("JDBC error:" + sqle.getMessage());
            sqle.printStackTrace();
          return conn;
      }then on every function I call it like
private int getFound(String UNumber) throws Exception {
        Connection conn = null;
        CallableStatement calstat=null;
        ResultSet rs = null;
        try {
            conn = pool.getConnection();
            calstat = (CallableStatement) conn.prepareCall("{call DuplicatePost(?)}");
            calstat.setString(1, UNumber);
            rs = calstat.executeQuery();
            tarCount = 0;
            while (rs.next()) {
                tarCount++;
        } catch (SQLException se) {
            System.out.println("JDBC error:" + se.getMessage());
            se.printStackTrace();
        } catch (Exception e) {
            System.out.println("other error:" + e.getMessage());
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) {
                    rs.close();
                if (calstat != null) {
                    calstat.close();
            } catch (SQLException e) {
                e.printStackTrace();
        } //end finally
        return tarCount;
    }// end function
}// end