Multithreading - MySQL java connector prepared statement use

Question

I have made a java class which runs in it's own thread that works through a queue of mysql queries so that it doesn't block the main application thread. I want to use prepared statements, however if I keep reusing the same prepared statement then if there's two or more of that same prepared statement in the queue (I use the same preparedstatement object for each query of that type), it will have the wrong params. If I make a new preparedstatement each time will it recompile the prepared statement each time it is run or will it detect that it's already been compiled and just execute?

Answer 1

I think you really wont be able to utilize Prepared Statement Pooling feature available in Java connection pooling implementations like Apache DBCP. This is because you are storing prepared statement objects in the queue. If you could store your SQL and paramenters in a custom class instead, and create / execute PreparedStatements in execution thread you can get the benefit of pooling by using something like DBCP

See DBCP configurations docs on how to enable statement pooling (poolPreparedStatements)

Answer 2

will it recompile the prepared statement each time it is run or will it detect that it's already been compiled and just execute?

It's up to the DBMS, not Java, but the general idea is that it can detect a reuse of an existing compiled statement and pools them under the hood, either in the driver or at the server. See the JDBC 4.0 Specification, #11.6, "Reuse of Statements by Pooled Connections".

Answer 3

From the java tutorial

If you want to execute a Statement object many times, it usually reduces execution time to use a PreparedStatement object instead.

The main feature of a PreparedStatement object is that, unlike a Statement object, it is given a SQL statement when it is created. The advantage to this is that in most cases, this SQL statement is sent to the DBMS right away, where it is compiled. As a result, the PreparedStatement object contains not just a SQL statement, but a SQL statement that has been precompiled. This means that when the PreparedStatement is executed, the DBMS can just run the PreparedStatement SQL statement without having to compile it first.

http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html#supply_values_ps