Question

Suppose I’m making a JDBC call and I had fetched data from a database to a ResultSet. But due to a network issue I lost my connection with the database.

(Connection, Statement and ResultSet is not closed in DB). Will I still be able to iterate over the ResultSet ?

Answer 1

Even if you could, you shouldn’t unless you are coding against a very specific jdbc driver. In some cases, the result set will not be constructed at all. In others (Oracle IIRC), you could configure it so that it only fetches a give number of rows out of the total.

However, in general, if you lose the connection, you have more things to worry about than wondering if you can iterate over a partially fetched resulst set object. In such cases, the rule of thumb is

1. to assume the worst;
2. attempt to close the result set,
   statement and connection; even if
   the physical connection is lost,
   there might be resources like memory
   and file handles on the calling side
   that need to be disposed off;
3. if possible, attempt to get a new
   connection (either a new physical
   one or from a connection pool) and
   start over.

Also, as a rule of thumb, you should not worry about partial failures when executing statements within a transaction. Discard and retry fresh.

In some rare cases the DB can send you a vendor specific code (SQLException.getErrorCode()) that can tell you whether the operation can be retried. Oracle has some specific codes (don’t remember them) for cases when you do an insert and a unique constrain has been violated. Sometimes such failed operations can be retried, but that’s vendor and business specific.

In general, just dump the mauled result set and start over.