Question

I want to know which is safe & better way to use Connection variable of following.

First : Connection as class member variable of class

class MyClass
{
    Connection conn;

    public MyClass(Connection conn) {
        this.conn = conn;
    }

    public void myMethod(){
        //Do some DB operations using conn
    }
}

Second : Initialize connection in method

class MyClass
{       
    public MyClass() {      
    }

    public void myMethod(){
        Connection conn= initializeFunction(); //Initialize Connection
        //Do some DB operations using conn
    }
}

Third : Send connection as argument to function

class MyClass
{       
    public MyClass() {      
    }

    public void myMethod(Connection conn){
        //Do some DB operations using conn
    }
}

NOTE : Question is not programming language specific, hence I have added tags other than Java as well.

Answer 1

When it comes to Database Connection object, the best is: To open as late as possible and close as early as possible.

In C# there is a using statement which works with objects implementing IDisposable interface. using statement works like try/finally block of code. IMO the general practice for handling connection should be something like:

try
{
connection = new Connection();
connection.Open(); // open the connection
//work with the connection, DB CRUD operations
}
finally
{
if(connection != null)
     connection.Close(); // close the connection in finally block
                         // so that even if the exception occurs, connection gets closed. 
}

For your options, I believe the first one is the worst, which holds the connetion object along with the object of the class.

I think you should be more concerned about opening/closing the connection rather than holding the object of the connection in multiple places.