Java not giving Error!

Question

Here is my code - i am simply checking my MySQL database connection.
But first i have compiled and run the program successfully. but then i have commented the line Class.forName .
Still when i compile it runs successfully, without any error.Why?

import java.sql.Connection;
import java.sql.DriverManager;


public class FirstJbdc {
    public static void main(String[] args) {
     Connection cn=null;
     try {
      //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
      System.out.println("Driver loaded successfully");
      cn=DriverManager.getConnection("jdbc:odbc:myDSN","root", "java");
      System.out.println("Database connected successfully....");
      System.out.println(cn);
     } catch (Exception e) {
      // TODO: handle exception
                        e.printStackTrace();
     }
    }
}

Answer 1

I throws an error, alright. It's just that the

catch (Exception e){
     // here the exception is instantiated, but nothing is done about it
}

clause silently swallows your exception.

Try a

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

in the catch clause

Answer 2

Java 1.6 can find JDBC driver even without using Class.forName.

Here is relevant part of documentation:

The DriverManager methods getConnection and getDrivers have been enhanced to support the Java Standard Edition Service Provider mechanism. JDBC 4.0 Drivers must include the file META-INF/services/java.sql.Driver. This file contains the name of the JDBC drivers implementation of java.sql.Driver. For example, to load the my.sql.Driver class, the META-INF/services/java.sql.Driver file would contain the entry:

my.sql.Driver

Applications no longer need to explictly load JDBC drivers using Class.forName(). Existing programs which currently load JDBC drivers using Class.forName() will continue to work without modification.

Answer 3

NOTE: this only applies to pre-JDBC 4.0 Drivers.

JDBC drivers are meant to have a static section that registers them with the java.sql.DriverManager when the class is loaded, hence the Class.forName(String) is required.

It's detailed here: http://java.sun.com/j2se/1.3/docs/guide/jdbc/getstart/drivermanager.html

Answer 4

try {

     //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
      System.out.println("Driver loaded successfully");
      cn=DriverManager.getConnection("jdbc:odbc:myDSN","root", "java");
      System.out.println("Database connected successfully....");
      System.out.println(cn);
} catch (Exception e) {
    // add the following statement
    System.out.println(e.getMessage());
}

If you add the statement inside the catch block, then compile and run, you should see the error message like-

[Some Com][Some Driver Manager] Data source name not found and no default driver specified

Answer 5

Without Class.forName(), the JDBC-ODBC bridge driver is not loaded. By JDBC specification, getConnection() returns null if no driver is found for the URL, no exception is thrown. So this is expected behavior.