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{{(!)| The use of external connection pools is available from '''3.0MP32'''}}

== Introduction ==

Openbravo uses connection pools to reuse existing connections/prepared statements, avoiding the cost of initiating a connection, parsing SQL etc. By default Openbravo uses two different connection pools:
* Hibernate default connection pool for DAL-related queries
* [http://commons.apache.org/proper/commons-dbcp/ Apache DBCP] for the connections provided by the ConnectionProviderImpl.

From 3.0MP32 it is possible to specify an external connection provider to replace these two connection pools. Openbravo provides a free commercial module that implements the Tomcat JDBC Connection Pool, but it is possible for developers to publish a module implement their own connection pool.

== ExternalConnectionPool abstract class ==

In order to implement an external connection pool, developers must subclass the ExternalConnectionPool abstract class. This class has three methods:

<source lang="java">/**
*
* @param externalConnectionPoolClassName
* The full class name of the external connection pool
* @return An instance of the external connection pool
*/
public final synchronized static ExternalConnectionPool getInstance(
String externalConnectionPoolClassName) throws InstantiationException,
IllegalAccessException, ClassNotFoundException;
</source>

The getInstance method is in charge of instantiating the external connection pool. The name of the class that implements the connection pool is passed as a parameter, its value is taken from the '''db.externalPoolClassName''' property of Openbravo.properties.

<source lang="java">/**
* @return A Connection from the external connection pool
*/
public abstract Connection getConnection()
</source>

This is the main method that should be overwritten by all external connection providers. It takes no arguments, and it should return a connection that has been borrowed from the pool.

<source lang="java">/**
* If the external connection pool supports interceptors this method should be overwritten
*
* @param interceptors
* List of PoolInterceptorProvider comprised of all the interceptors injected with Weld
*/
public void loadInterceptors(List<PoolInterceptorProvider> interceptors)
</source>

This method should be overwritten if the connection pool supports interceptors and allows custom interceptors to be instantiated using dependency injection. A list of PoolInterceptorProvider will be passed as an arguments, containing the full class name of the interceptors.

== Design Considerations ==

* Include a configuration file so that users can customize the external connection pool to meet their needs.
* If the pool needs to execute some initialization code, place it in the getConnection method and make sure that is only executed the first time that method is invoked.
* For all connection returned by the pool:
** SessionInfo.setDBSessionInfo(Connection conn, String rdbms) must be executed
** The sql query included in the '''bbdd.sessionConfig''' property must be executed using that connection.
* Take into account that these two operations must be executed on the returned connection only when the connection is actually created, not every time it is returned from the pool.

[[Category:HowTo]]

How to Create an External Connection Pool - Revision history

Wikiadmin: Created page with "{{(!)| The use of external connection pools is available from '''3.0MP32'''}} == Introduction == Openbravo uses connection pools to reuse existing connections/prepared state..."