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See:
Description
| Interface Summary | |
| ConnectionFactory | Abstract factory interface for creating Connections. |
| Class Summary | |
| BasicDataSource | Basic implementation of javax.sql.DataSource that is
configured via JavaBeans properties. |
| BasicDataSourceFactory | JNDI object factory that creates an instance of
BasicDataSource that has been configured based on the
RefAddr values of the specified Reference,
which must match the names and data types of the
BasicDataSource bean properties. |
| DataSourceConnectionFactory | A DataSource-based implementation of ConnectionFactory. |
| DelegatingCallableStatement | A base delegating implementation of CallableStatement. |
| DelegatingConnection | A base delegating implementation of Connection. |
| DelegatingPreparedStatement | A base delegating implementation of PreparedStatement. |
| DelegatingResultSet | A base delegating implementation of ResultSet. |
| DelegatingStatement | A base delegating implementation of Statement. |
| DriverConnectionFactory | A Driver-based implementation of ConnectionFactory. |
| DriverManagerConnectionFactory | A DriverManager-based implementation of ConnectionFactory. |
| PoolableConnection | A delegating connection that, rather than closing the underlying
connection, returns itself to an ObjectPool when
closed. |
| PoolableConnectionFactory | A PoolableObjectFactory that creates
PoolableConnections. |
| PoolablePreparedStatement | A DelegatingPreparedStatement that cooperates with
PoolingConnection to implement a pool of PreparedStatements. |
| PoolingConnection | A DelegatingConnection that pools PreparedStatements. |
| PoolingDataSource | A simple DataSource implementation that obtains
Connections from the specified ObjectPool. |
| PoolingDriver | A Driver implementation that obtains
Connections from a registered
ObjectPool. |
| Exception Summary | |
| SQLNestedException | A SQLException subclass containing another Throwable |
Database Connection Pool API.
Overview in Dialog FormQ: How do I use the DBCP package?
A: There are two primary ways to access the DBCP pool, as a
Driver, or as a DataSource.
You'll want to create an instance of PoolingDriver or
PoolingDataSource. When using one of these
interfaces, you can just use your JDBC objects the way you normally would.
Closing a Connection will simply return it to its pool.
Q: But PoolingDriver and
PoolingDataSource both expect an
ObjectPool as an input. Where do I
get one of those?
A: The ObjectPool interface is defined
in the org.apache.commons.pool package (Commons-Pool).
The org.apache.commons.pool.impl package has a couple of implementations,
and you can always create your own.
Q: Ok, I've found an ObjectPool
implementation that I think suits my connection pooling needs. But it wants
a PoolableObjectFactory.
What should I use for that?
A: The DBCP package provides a class for this purpose. It's called
PoolableConnectionFactory.
It implements the factory and lifecycle methods of
PoolableObjectFactory
for Connections. But it doesn't create the actual database
Connections itself, if uses a
ConnectionFactory for that.
The PoolableConnectionFactory will take
Connections created by the ConnectionFactory
and wrap them with classes that implement the pooling behaviour.
Several implementations of ConnectionFactory are
provided--one that uses DriverManager to create connections
(DriverManagerConnectionFactory),
one that uses a Driver to create connections
(DriverConnectionFactory),
one that uses a DataSource to create connections
(DataSourceConnectionFactory).
Q: I think I'm starting to get it, but can you walk me though it again?
A: Sure. Let's assume you want to create a DataSource
that pools Connections. Let's also assume that that
those pooled Connections should be obtained from
the DriverManager.
You'll want to create a PoolingDataSource.
The PoolingDataSource uses an underlying
ObjectPool to create and store its
Connection.
To create a ObjectPool, you'll need
a PoolableObjectFactory that creates
the actual Connections. That's what
PoolableConnectionFactory is for.
To create the PoolableConnectionFactory,
you'll need at least two things:
ConnectionFactory from which
the actual database Connections will be obtained.
ObjectPool
in which the Connections will be stored.
ObjectPool into the
PoolableConnectionFactory, it will
automatically register itself as the PoolableObjectFactory
for that pool.
KeyedObjectPoolFactory
that will be used to create KeyedObjectPools for
pooling PreparedStatements for each Connection.
In code, that might look like this:
GenericObjectPool connectionPool = new GenericObjectPool(null);
DriverManagerConnectionFactory connectionFactory = new DriverConnectionFactory("jdbc:some:connect:string",null);
PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory,connectionPool,null,null,false,true);
PoolingDataSource dataSource = new PoolingDataSource(connectionPool);
To create a PoolingDriver, we do the same thing,
except that instead of creating a DataSource on the last line,
we create a PoolingDriver, and register the
connectionPool with it. E.g.,:
GenericObjectPool connectionPool = new GenericObjectPool(null);
DriverManagerConnectionFactory connectionFactory = new DriverConnectionFactory("jdbc:some:connect:string",null);
PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory,connectionPool,null,null,false,true);
PoolingDriver driver = new PoolingDriver();
driver.registerPool("example",connectionPool);
Since the PoolingDriver registers itself
with the DriverManager when it is created, now you can just
go to the DriverManager to create your Connections,
like you normally would:
Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:example");
Q: Sounds complicated, is there an easier way?
A: If you're using the PoolingDriver, you
don't need to do this configuration in code. Instead, you can provide
a JOCL document that describes the connection pool,
and let the PoolingDriver discover it at
runtime.
Specifically, if the PoolingDriver is asked for
a Connection from a pool that has not yet been registered,
it will look for a named resource from which to read the pool's configuration,
and create that pool.
For example, suppose you create a pool named "/eg" from a JOCL
document. The "connect string" for this pool will be
"jdbc:apache:commons:dbcp:/eg". To do this, you'll need a create
a resource (just a file in your classpath) containing a JOCL description
of the pool. Specifically, this JOCL document should define a
PoolableConnectionFactory from which the
pool will be obtained. For example:
<object class="org.apache.commons.dbcp.PoolableConnectionFactory" xmlns="http://apache.org/xml/xmlns/jakarta/commons/jocl">
<!-- the first argument is the ConnectionFactory -->
<object class="org.apache.commons.dbcp.DriverManagerConnectionFactory">
<string value="jdbc:some:connect:string"/>
<object class="java.util.Properties" null="true"/>
</object>
<!-- the next argument is the ObjectPool -->
<object class="org.apache.commons.pool.impl.GenericObjectPool">
<object class="org.apache.commons.pool.PoolableObjectFactory" null="true"/>
<int value="10"/> <!-- max active -->
<byte value="1"/> <!-- when exhausted action, 0 = fail, 1 = block, 2 = grow -->
<long value="2000"/> <!-- max wait -->
<int value="10"/> <!-- max idle -->
<boolean value="false"/> <!-- test on borrow -->
<boolean value="false"/> <!-- test on return -->
<long value="10000"/> <!-- time between eviction runs -->
<int value="5"/> <!-- number of connections to test per eviction run -->
<long value="5000"/> <!-- min evictable idle time -->
<boolean value="true"/> <!-- test while idle -->
</object>
<!-- the next argument is the KeyedObjectPoolFactory -->
<object class="org.apache.commons.pool.StackKeyedObjectPoolFactory">
<int value="5"/> <!-- max idle -->
</object>
<string value="SELECT COUNT(*) FROM DUAL"/> <;!-- validation query -->
<boolean value="false"/> <!-- default read only -->
<boolean value="true"/> <!-- default auto commit -->
</object>
Simply save that file somewhere in your classpath as eg.jocl,
and the PoolingDriver will find it
automatically. You need only register the PoolingDriver
(for example, using the jdbc.drivers property), and use the
the DriverManager to create your Connections,
like you normally would:
Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:/eg");
(Note that without the leading slash, the pool must be located at
org/apache/commons/dbcp/PoolingDriver/eg.jocl within your classpath.
See Class.getResource(java.lang.String) for details.)
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