CODEWITHSUNDEEP
javajdbc
Sriram
Sriram

Reputation: 2999

Closing Connection object once I got my required ResultSet

Would there be any effect if I close my Connection object once I got my ResultSet?

Connection con= DriverManager.getConnection();
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(query);
con.close();

Further to this I use my rs object and I feel there will not be any impact on it. Because ResultSet and Statement are in connection with each other.

Upvotes: 2

Views: 1095

Answers (4)

Sankar
Sankar

Reputation: 172

You can't access the resultset soon after you close the connection to the database. Because, when you use resultset.next() method, it will send a request to the database in order to fetch the next record; but physically the connection has been closed. So, an Exception will be thrown by your statement resultset.next().

Upvotes: 3

Faelkle
Faelkle

Reputation: 485

You mustn't use anything derived from a Connection after the connection is closed.

This is actually because things like Result Sets might not be transferred to your machine until you actually use them. Databases can and do use transfer batching and server cursors - which is a complicated way of saying they only transfer a block of rows to you as you actually request them by moving the result set cursor (for instance with ResultSet#next()).

Other parts of the result set, like BLOB or other LOB types, aren't transferred at all until you actually read them out of the result set. That's because they can be arbitrarily large and the DB driver (okay, a good DB driver) wants to minimize the memory it uses in the client.

The DB server itself is usually vastly more sophisticated than the driver (which becomes little more than a communications arbiter), and it's best to leave the 'heavy lifting' (marshalling and temporary storage of result sets) to the DB :-)

So you can see that closing a connection is going to free all the server resources - and there could be many - associated with your query.

Upvotes: 3

m0skit0
m0skit0

Reputation: 25873

You cannot close the connection if you want to access the ResultSet after closing. You will lose the ResultSet data and will get an exception when you try to access it.

This is because ResultSet instances are linked to the DB connection.

Upvotes: 2

Azodious
Azodious

Reputation: 13872

Once the Connection is closed other resources (Statements or ResultSets) must not be used.

Upvotes: 3

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