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Thread: problems with connection to mysql database

  1. #1
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    Default problems with connection to mysql database

    When i try to execute the ListProdQty method it jumps from that method to the catch in the connecttodatabase method and gives me a java.lang.NullPointerException
    public void ConnectToDatabase()
    {
        try
        {
        String user, pass, host;
        user = readEntry("Please enter User ID  : ");
        pass = readEntry("Please enter Password : ");
        host = readEntry("Please enter Hostname : ");
       // database = readEntry("Please enter database name: ");
        //  userid, password and hostname are obtained from the console
     
        Connection conn = DriverManager.getConnection
    	              ("jdbc:mysql://localhost:3306/oncs", user, pass);
     
        /* JDBC default is to commit each SQL statement as it is sent to the database.  Setting autocommmit=false changes the default
           behaviour so that transactions have to be committed explicity.
         */
        conn.setAutoCommit(false);
        MenuMain();
        }
        catch(Exception ex)
        {
        	System.out.println(ex);
        }
      } 
     
     
     
     
     
    private void ListProdQty()
        {
        try
        	{
        	// Creates a statement and a result set to execute the sql query.
    			s = conn.createStatement();
    			resultSet = s.executeQuery("SELECT pname FROM product"+
    				"WHERE pqtyinstock >5"+
    					" AND pretailprice > 150"+
    						"ORDER BY pname");
     
    			//Creates a loop to loop through the result set
    			while(resultSet.next()) 
          {
          	//Prints the results to the user
    	 		  System.out.println(resultSet.getString(1));
          }
          //Commits the connection to the database
          conn.commit();
     
        	}
        	catch(SQLException excep)
        	{
        		//Prints an error message to the user
        		System.out.println(excep);
        	}
        }
    Last edited by thepower; April 18th, 2010 at 02:05 PM.


  2. #2
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    Default Re: problems with connection to mysql database

    Hey thepower,

    First of all, welcome to the forum

    And then youre code; I see in ListProdQty() that you call conn.createStatement() but! I dont see what conn is actually holding (and think this is part of youre problem).

    In ConnectToDatabase() I do see you defining conn as a Connection with a connection provided by the Drivermanager. But! I dont see you putting conn into a attribute of the class or a way that conn in ListprodQty() knows that it was defined in ConnectToDatabase(). Try fixing this first.

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