Insert - database

Question

Hello All...I have a question ...When we insert a record into the database using jdbc and if that record cannot be inserted as it violates primary key / duplicate key and throws an exception...how can we handle such situation ...do we need to show the user that the record cannot be inserted as it already exists in the database...and if yes how to check it
help is greatly appreciated...
Thansk,
Greeshma

Answer 1

The Connection object has a method, setAutoCommit() and a property autoCommit.
con.setAutoCommit(false);would set turn off auto commit. So all data would be entered into the database, but not committed. If you think everything is ok, you would call,
con.commit();else, in case exceptions are thrown, call,
con.rollback();j
This basically allows you to make transactions on the database and rollback if it fails.
By the way, you should turn on auto commit once you finish with your transaction so that at other places, you do not accidently use a connection that you will need to explicitly call commit() on.
Your code should be something like this:
try
    con.setAutoCommit(false);
    try
        //execute your preparedstatement
        //once you're done, i.e after your loop or whatever and you're sure you've entered all data, commit
        con.commit();
    catch ( Exception e )
        con.rollback(); //undo whatever inserts may have happened
catch ( Exception e )
    System.out.println("Unable to turn off auto-commit: " + e );
finally
    //try to put autocommit back on
    try
        con.setAutoCommit(true);
       //not sure but I think an exception is thrown if it is already true
    catch ( Exception e )
        System.out.println("Failed to turn on autocommit: " + e );
}