USING AN SQL WORKLOAD - HTTP Programming Recipes for Java Bots - page 508

Obtaining a PreparedStatement
Other than allowing statements to be repeated, the other major function provided by the
RepeatableStatement class is the ability to allocate PreparedStatement
objects to threads. Two threads cannot use the same PreparedStatement object at
the same time. To keep threads from using the same PreparedStatement object, the
obtainStatement and releaseStatement functions are used.
The first thing that the obtainStatement function does, is to check to see if it
can acquire the mutex . This prevents two threads from calling obtainStatement at
exactly the same time.
PreparedStatement result = null;
try {
this.mutex.acquire();
If there are no extra statements already in the cache, then create a new
PreparedStatement .
if (this.statementCache.size() == 0) {
result = this.manager.getConnection().prepareStatement(this.sql);
If there is an extra PreparedStatement in the cache, then return that
PreparedStatement and remove it from the cache.
} else {
result = this.statementCache.get(0);
this.statementCache.remove(0);
}
} catch (InterruptedException e) {
return null;
Once we are done, we can release the mutex .
} finally {
this.mutex.release();
}
return result;
Once you are finished with the PreparedStatement that we obtained, call
releaseStatement to return it to the cache.
Releasing a PreparedStatement
When a PreparedStatement is released by calling releaseStatment ,
the PreparedStatement is not actually released. Rather, it is simply returned to the
PreparedStatement cache. This saves the program the overhead of allocating and
releasing large numbers of PreparedStatement objects.