JDO provides a standard utility that gives access to useful parts of the JDO persistence process. This is known as JDOHelper (javax.jdo.JDOHelper)

PersistenceManagerFactory methods

The methods in JDOHelper can be split into categories. Here we start with the methods for creating the starting point for persistence, the PersistenceManagerFactory (PMF)

• getPersistenceManagerFactory(Map props) - creates a PMF given a Map of the properties
• getPersistenceManagerFactory(Map props, ClassLoader cl) - creates a PMF given a Map of the properties, and a ClassLoader to use
• getPersistenceManagerFactory(String resource) - creates a PMF given a resource defining the properties. This can be used to create a named PMF in JDO2.1
• getPersistenceManagerFactory(String props, ClassLoader cl) - creates a PMF given a resource defining the properties, and a ClassLoader to use
• getPersistenceManagerFactory(File props) - creates a PMF given a file containing the properties
• getPersistenceManagerFactory(File props, ClassLoader cl) - creates a PMF given a file containing the properties and a ClassLoader to use
• getPersistenceManagerFactory(String jndi, Context ctx) - creates a PMF given a JNDI resource
• getPersistenceManagerFactory(String jndi, Context ctx, ClassLoader cl) - creates a PMF given a JNDI resource and a ClassLoader to use
• getPersistenceManagerFactory(InputStream strm) - creates a PMF given an InputStream
• getPersistenceManagerFactory(InputStream strm, ClassLoader cl) - creates a PMF given an InputStream and a ClassLoader to use

Persistence methods

Now we move onto the operations for persistence.

• getPersistenceManager(Object pc) - returns the PersistenceManager associated with the passed object (if any)
• makeDirty(Object pc, String fieldName) - marks the field of the passed object as dirty (meaning that it needs updating in its datastore)
• getObjectId(Object pc) - returns the object identity for the passed object (if persistent)
• getObjectIds(Collection pc) - returns the object identities for the passed objects (if persistent)
• getObjectIds(Object[] pc) - returns the object identities for the passed objects (if persistent)
• getVersion(Object pc) - returns the version for the passed object (if persistent)

Lifecycle methods

Now we move onto lifecycle operations

• getObjectState(Object pc) - returns the object state
• isDirty(Object pc) - returns whether the passed object is dirty
• isTransactional(Object pc) - returns whether the passed object is transactional
• isPersistent(Object pc) - returns whether the passed object is persistent
• isNew(Object pc) - returns whether the passed object is new
• isDeleted(Object pc) - returns whether the passed object is deleted
• isDetached(Object pc) - returns whether the passed object is detached