Null pointer exception in con.createStatement(); (Struts 2 using netbeans6.1 and MYSQL)

[Hrishikesh Maluskar]

i am creating a application in struts2 using netbeans 6.1. I have done database connection with MYSQL from netbeans. It also shows connection successful , but gives null pointer exception on this line -> con.createStatement();

Log is as folllows->

java.lang.NullPointerException
at net.roseindia.Login.execute(Login.java:57)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly

[Herman Schelti]

hi,

then con is null.

how do you initialize this variable con? (post some code)

Herman

[Hrishikesh Maluskar]

i have pasted the code below , it shows null pointer exception on the line indicated as ##.

   String url = "jdbc:mysql://localhost:3306/";
    String dbName = "WEBDB";
    String driverName = "org.gjt.mm.mysql.Driver";
    String userName = "root";
    String password = "root";
    Connection con=null;
    Statement stmt=null;
     ResultSet rst=null;
    int val=0,flag=0;
    try{
      Class.forName(driverName).newInstance();
      con=DriverManager.getConnection(url+dbName, userName, 
          password);
      stmt=con.createStatement();
    }
    catch(Exception e){
      System.out.println(e.getMessage());
    }
    
   
     try{
     ## stmt = con.createStatement();
     rst = stmt.executeQuery("SELECT USER_NAME ,PASSWORD ,CONCAT(F_NAME,' ',L_NAME) NAME FROM USR_DTLS"); 
     }catch(Exception ex){
    	ex.printStackTrace();
   	 } 

[Herman Schelti]

hi,

my guess is that

  Class.forName(driverName).newInstance(); 

throws a ClassNotFoundException

 System.out.println(e.getMessage());    

might be in your log, but it's only 1 line, easy to overlook.

Why not change it into

System.out.println("==> there it is!!!" + e.getMessage());     

Good luck!

Herman
PS Please copy/paste from your log if you reply.

[Hrishikesh Maluskar]

try{
      Class.forName(driverName).newInstance();
      con=DriverManager.getConnection(url+dbName, userName, 
          password);
      stmt=con.createStatement();
    }
    catch(Exception e){
      System.out.println("**************************************here it is="+e.getMessage());
    }
    

for the above code i got the following error in the log...how to get around it

  **************************************here it is=com.mysql.jdbc.Driver
  

[Herman Schelti]

hi,

if the e.getMessage() does not give enough information, add the class of the exception

 
System.out.println("**************************************here it is="+e.getMessage() + "/" + e.getClass());
 

It will probably give you a ClassNotFoundException, here's how to solve it:

If you have a connection from Netbeans to your MySQL database, that does not mean that your application can connect to the MySQL database.
You will have to add the mysql driver (the .jar file that it's in) to your webapplication (just put the jar file the lib folder of your webapplication), or add that .jar file to the classpath of your server.

Herman

[Hrishikesh Maluskar]

Thanks herman...now i am able to connect to MYSQL