Date: 2004-05-20T04:39:47
Editor: DirkVerbeeck <[EMAIL PROTECTED]>
Wiki: Jakarta Commons Wiki
Page: DBCP
URL: http://wiki.apache.org/jakarta-commons/DBCP
Moved page from old wiki
New Page:
Is this project still active or have they just not released anything in an excessive
period of time?
DBCP is still active. It is an active area of discussion right now on the commons-dev
mailing list, and has had a number of recent commits.
----
What is the best way, ASIDE from running a query against the DB, to be sure that the
connection is still valid when it is retrieved from the pool?
1) this question may be better posed on commons-user or commons-dev.
2) how would you do this without a pool? I.e., what is the best way aside from
running a query to be sure that a connection is still valid when returned from
DriverManager/DataSource.getConnection?
----
When upgrading from DBCP 1.0 to DBCP 1.1 you can encounter the following issue
(reported on commons-user):
We are accessing mainframe data using a JDBC
driver, but it is not truly a database. Specifically, the setAutoCommit and
setReadOnly Connection methods fail. Version 1.0 of DBCP silently discarded
these errors and allowed the connections to be created and used anyway.
Version 1.1 of activateObject surfaces these exceptions and fails to create
new connections in the pool.
(solution: use custom activateObject method)
----
Q: I see in the javadocs that AbandonedConnectionPool was deprecated (DBCP 1.1). What
replaced it?
A: The original reason for deprecation was the danger in reusing a abandoned
connection without knowing if it is safe to do so. There was a discussion about it in
april. Some people wanted to remove it completely.
I took a different approach. In 1.1 an abandoned connection will not be reused but
closed (and a new one created).
The classes remained deprecated because I think the AbandonedPool should move to the
pool package (and made more generic/safe).
The abandoned connection feature on BasicDataSource will remain supported in one form
or another. I'm not using it on my tomcat production configurations but there are
junit tests to make sure everything works.
So if you are using the Abandoned* classes directly then it is possible you are
affected by a future refactoring (we will try to remain compatible if possible of
course). If you use BasicDataSource then you can be sure the feature will remain.
----
Q: When using DBCP what parameter needs to be set on the ObjectPool so that a
minimum number of connections are created when the pool instance is created
? I thought the setMinIdle() does this, but doesn't look so.
A: You can setMinIdle() to always have a minium amount of idle connection in the pool.
(not only at the start of the pool but the whole time)
The minIdle check is done in the evictor thread so timeBetweenEvictionRunsMillis has
to be set to a non negative-value. (you can optionally turn off the eviction by
setting numTestsPerEvictionRun to zero or just set minEvictableIdleTimeMillis very
high).
A more simple way to create a number of connections at startup is to use the
pool.addObject() method.
(add the following after creating the PoolableConnectionFactory)
for (int i=0 ; i<initialsize ; i++) {
connectionPool.addObject()
}
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Q: <nowiki>Does the current 1.1 release support the poolable/caching of
PreparedStatements. I noted that the PoolableConnectionFactory can take a
KeyedObjectPoolFactory as a statement pool factory. But there is not concrete
implementation for the KeyedPoolableObjectFactory which is required when creating a
GenericKeyedObjectPoolFactory. If I pass in a null as shown in the examples, does it
cache prepared statements or should I do that in local objects?</nowiki>
A: ??
----
Q: Where do I get a concrete example of PerUserPoolDataSource? How do we use it in a
situation where multiple pools are required for different modules of a project and
their properties differ on the database transactional load?
----
Here's a little diagram showing what datastructure DBCP sets up and how that
datastructure is used in case the DriverManager is
employed to obtain Drivers at runtime. Please send any corrections (for now) to [EMAIL
PROTECTED]
* http://rei1.m-plify.net/Apache_DBCP/Apache_DBCP_Structure.pdf
* http://rei1.m-plify.net/Apache_DBCP/Apache_DBCP_Structure.vsd
There is also a *PNG* image but I don't include the link here because the Wiki
includes it directly and it's a tad large.
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