When you create a PersistenceManagerFactory / EntityManagerFactory you define the connection URL, driver name, and the username/password to use. This works perfectly well but does not "pool" the connections so that they are efficiently opened/closed when needed to utilise datastore resources in an optimum way. DataNucleus allows you to utilise a connection pool using BoneCP to efficiently manage the connections to the datastore.

BoneCP is a third-party library providing connection pooling. This is accessed by specifying the persistence property datanucleus.connectionPoolingType . To utilise BoneCP-based connection pooling we do this

// Specify our persistence properties used for creating our PMF/EMF
Properties props = new Properties();
properties.setProperty("javax.jdo.PersistenceManagerFactoryClass",
                "org.datanucleus.jdo.JDOPersistenceManagerFactory");
properties.setProperty("datanucleus.ConnectionDriverName","com.mysql.jdbc.Driver");
properties.setProperty("datanucleus.ConnectionURL","jdbc:mysql://localhost/myDB");
properties.setProperty("datanucleus.ConnectionUserName","login");
properties.setProperty("datanucleus.ConnectionPassword","password");
properties.setProperty("datanucleus.connectionPoolingType", "BoneCP");

So the PMF / EMF will use connection pooling using BoneCP. To do this you will need the datanucleus-connectionpool plugin to be in the CLASSPATH, along with the BoneCP JAR.

You can also specify persistence properties to control the actual pooling. The currently supported properties for BoneCP are shown below

# Pooling of Connections
datanucleus.connectionPool.maxPoolSize=5
datanucleus.connectionPool.minPoolSize=3

# Pooling of PreparedStatements
datanucleus.connectionPool.maxStatements=20