Chapter III: JDO Technology Framework
The following figure depicts the relationship between the basic components of the JDO framework.
JDOHELPER.javax.jdo.jdoHelper contains some static auxiliary methods. These methods are used to query the survival of persistent objects and create an instance of PersistenceManagerFactory in a manner-independent manner.
PersistenceManagerFactory .javax.jdo.PersistenceManagerFactory is a factory in PersistenceManagers.
PersistenceManager.javax.jdo.PersistenceManager is the main interface used by the application. Each PersistenceManager manages a bunch of persistent objects and provides an API function for persistence and delete existing persistent objects for new objects. PersistenceManager and transactions are one-on-one relationship. And for both Extent and Query, PersistenceManager is their factory.
PersistenceCapable. Custom-Defined Sustainable Classes must implement a javax.jdo.spi.PersistenceCapable interface. Most JDO implementations provide an enhancer that transparently adds code for each sustainable class. You don't need to use this interface directly.
There is a pair of correspondence between each PersistenceManager and Transaction. The transaction allows for a variety of operation of persistent data to group, this group of operations is either successful or fail. This operation is important for the integrity of maintenance data.
Extent.javax.jdo.extent is a logical view of a class all objects stored in the data. By configuration, the extent can contain a subclass. Extent can be obtained from the PersistenceManager.
Query.javax.jdo.query This interface is implemented by a specific JDO providing vendor, transforming query expressions into Java data object query language (JDOQL), JDOQL based on Java Boolean expressions, translates into query languages of local databases. You can get a query instance from PersistenceManager.
The rest of the document details the JDO interface. We are listed in the order used in your development program. 3.1. JDO Abnormal Chart describes the relationship between JDO anomalies and it. JDO will throw your own anomalies and do not have an abnormal runtime.
