org.exolab.castor.persist.spi

Interface Persistence

All Known Implementing Classes:

SQLEngine

public interface Persistence

The persistence engine implements this interface in order to allow objects to be created, removed, loaded, stored, locked and checked for dirtyness.

The caller takes full responsibility to assure integrity of transactions and object caching and only relies on the engine to assist in assuring that through the mechanisms available to it.

All method calls provide an open connection into the persistence storage. The connection is opened by and maintained in the context of a transaction. The type of the connection depends on the persistence engine (JDBC, JNDI, etc).

All method calls provide the object fields and the object identity. The engine must always use the identity passed in the method call and never the identity contained in the object itself.

The stamp is an arbitrary object that is returned on object creation and loading and passed when performing a dirty check. The stamp can be used to detect object dirtyness in a more efficient manner in database that support a stamping mechanism (e.g. Oracle RAWID, Sybase TIMESTAMP).

An implementation of this object must be re-entrant and thread safe. It must depend on the connection passed in each method call and never hold a reference to a connection.

Version:

$Revision: 8752 $ $Date: 2006-04-26 16:24:34 -0600 (Wed, 26 Apr 2006) $

Author:

Assaf Arkin

See Also:

TransactionContext, PersistenceQuery

Method Summary

Methods

Modifier and Type	Method and Description
Identity	create(Database database, Object conn, ProposedEntity entity, Identity identity) Creates a new object in persistence storage.
PersistenceQuery	createQuery(QueryExpression query, Class<?>[] types, AccessMode accessMode) Creates and returns a new query object.
SQLRelationLoader	createSQLRelationLoader(String manyTable, String[] idSQL, int[] idType, TypeConvertor[] idTo, TypeConvertor[] idFrom, String[] relatedIdSQL, int[] relatedIdType, TypeConvertor[] ridTo, TypeConvertor[] ridFrom)
void	delete(Object conn, Identity identity) Deletes the object from persistent storage, given the object' identity.
void	load(Object conn, ProposedEntity proposedObject, Identity identity, AccessMode accessMode) Loads the object from persistence storage.
void	store(Object conn, Identity identity, ProposedEntity newentity, ProposedEntity oldentity) Stores the object in persistent storage, given the object fields and its identity.

Method Detail

create

Identity create(Database database,
              Object conn,
              ProposedEntity entity,
              Identity identity)
                throws PersistenceException

Creates a new object in persistence storage. Called for an object that was created during the transaction when the identity of that object is known. Creates a new record in persistence storage. Must detect an attempt to create an object with the same identity and must retain a lock on the object after creation. If the identity is null, an identity might be created and returned by this method.

Parameters:

conn - An open connection

entity - The fields to store

identity - The object's identity

Returns:

The object's identity

Throws:

PersistenceException - An object with the same identity already exists in persistent storage or any other persistence error occured.

load

void load(Object conn,
        ProposedEntity proposedObject,
        Identity identity,
        AccessMode accessMode)
          throws PersistenceException

Loads the object from persistence storage. This method will load the object fields from persistence storage based on the object's identity. This method may return a stamp which can be used at a later point to determine whether the copy of the object in persistence storage is newer than the cached copy (see store(java.lang.Object, org.exolab.castor.persist.spi.Identity, org.castor.persist.ProposedEntity, org.castor.persist.ProposedEntity)). If lock is true the object must be locked in persistence storage to prevent concurrent updates.

Parameters:

conn - An open connection

proposedObject - The fields to load into

identity - object's identity

accessMode - The access mode (null equals shared)

Throws:

PersistenceException - The object was not found in persistent storage or any other persistence error occured.

store

void store(Object conn,
         Identity identity,
         ProposedEntity newentity,
         ProposedEntity oldentity)
           throws PersistenceException

Stores the object in persistent storage, given the object fields and its identity. The object has been loaded before or has been created through a call to create(org.exolab.castor.jdo.Database, java.lang.Object, org.castor.persist.ProposedEntity, org.exolab.castor.persist.spi.Identity). This method should detect whether the object has been modified in persistent storage since it was loaded. After this method returns all locks on the object must be retained until the transaction has completed. This method may return a new stamp to track further updates to the object.

If the object was not retrieved for exclusive access, this method will be asked to perform dirty checking prior to storing the object. The original argument will contains the object's original fields as retrieved in the transaction, and stamp the object's stamp returned from a successful call to load(java.lang.Object, org.castor.persist.ProposedEntity, org.exolab.castor.persist.spi.Identity, org.exolab.castor.mapping.AccessMode). These arguments are null for objects retrieved with an exclusive lock.

Parameters:

conn - An open connection

newentity - The fields to store

identity - The object's identity

oldentity - The original fields, or null

Throws:

PersistenceException - The object has been modified in persistence storage since it was last loaded or has been deleted from persitence storage or any other persistence error occored.

delete

void delete(Object conn,
          Identity identity)
            throws PersistenceException

Deletes the object from persistent storage, given the object' identity. The object has been loaded before or has been created through a call to create(org.exolab.castor.jdo.Database, java.lang.Object, org.castor.persist.ProposedEntity, org.exolab.castor.persist.spi.Identity). After this method returns all locks on the object must be retained until the transaction has completed.

Parameters:

conn - An open connection

identity - The object's identity

Throws:

PersistenceException - A persistence error occured

createQuery

PersistenceQuery createQuery(QueryExpression query,
                           Class<?>[] types,
                           AccessMode accessMode)
                             throws QueryException

Creates and returns a new query object. The query object is used to execute a query against persistent storage and fetch the results of the query. The query parameter types are specified prehand. If a particular parameter type is unknown, null may be used and type checking will defer to query execution.

Parameters:

query - The query expression

types - List of all parameter types, or null

Returns:

A new query object that can be executed

Throws:

QueryException - The query is invalid

createSQLRelationLoader

SQLRelationLoader createSQLRelationLoader(String manyTable,
                                        String[] idSQL,
                                        int[] idType,
                                        TypeConvertor[] idTo,
                                        TypeConvertor[] idFrom,
                                        String[] relatedIdSQL,
                                        int[] relatedIdType,
                                        TypeConvertor[] ridTo,
                                        TypeConvertor[] ridFrom)