8.5 Database Connection Management

The Oracle RDF Graph Adapter for Eclipse RDF4J provides support for Oracle Connection Pooling.

Instances of OracleSailStore use a connection pool to manage connections to an Oracle AI Database. Oracle Connection Pooling is provided through the OraclePool class. Usually, OraclePool is initialized with a DataSource, using the OraclePool (DataSource ods) constructor. In this case, OraclePool acts as an extended wrapper for the DataSource, while using the connection pooling capabilities of the data source. When you create an OracleSailStore object, it is sufficient to specify the OraclePool object in the store constructor, the database connections will then be managed automatically by the adapter for Eclipse RDF4J. Several other constructors are also provided for OraclePool, which, for example, allow you to create an OraclePool instance using a JDBC URL and database username and password. See the Javadoc included in the Oracle RDF Graph Adapter for Eclipse RDF4J download for more details.

If you need to retrieve Oracle connection objects (which are essentially database connection wrappers) explicitly, you can invoke the OraclePool.getOracle method. After finishing with the connection, you can invoke the OraclePool.returnOracleDBtoPool method to return the object to the connection pool.

When you get an OracleSailConnection from OracleSailStore or an OracleSailRepositoryConnection from an OracleRepository, a new OracleDB object is obtained from the OraclePool and used to create the RDF4J connection object. READ_COMMITTED transaction isolation is maintained between different RDF4J connection objects.

The one exception to this behavior occurs when you obtain an OracleSailRepositoryConnection by calling the asRepositoryConnection method on an existing instance of OracleSailConnection. In this case, the original OracleSailConnection and the newly obtained OracleSailRepositoryConnection will use the same OracleDB object. When you finish using an OracleSailConnection or OracleSailRepositoryConnection object, you should call its close method to return the OracleDB object to the OraclePool. Failing to do so will result in connection leaks in your application.