JDO Interface

PersistenceCapable

A class that can be managed by a binary-compatible JDO implementation must implement this interface.

This interface defines methods that allow the implementation to manage the instances. It also defines methods that allow a JDO aware application to examine the runtime state of instances. For example, an application can discover whether the instance is persistent, transactional, dirty, new, deleted, or detached; and to get its associated PersistenceManager, object identity, and version if it has one.

In the Reference Implementation, the JDO Enhancer modifies the class to implement PersistenceCapable prior to loading the class into the runtime environment. The Reference Enhancer also adds code to implement the methods defined by PersistenceCapable.

The extra methods in the PersistenceCapable interface might be generated by pre-processing a .java file, or might be generated from a tool directly. The exact technique for generating the extra methods is not specified by JDO.

The PersistenceCapable interface is designed to avoid name conflicts in the scope of user-defined classes. All of its declared method names are prefixed with 'jdo'.

Since:: JDO 1.0

Public Methods

Copy field values from another instance of the same class to this instance.

This method will throw an exception if the other instance is not managed by the same StateManager as this instance.

Parameters:: other - the PC instance from which field values are to be copied; fieldNumbers - the field numbers to be copied into this instance

Since:: JDO 1.0

Copy fields to an outside consumer from the key fields in the ObjectId.

This method is generated in the PersistenceCapable class to generate a call to the field manager for each key field in the ObjectId. For example, an ObjectId class that has three key fields

(int id,
 String name, and Float salary)

would have the method generated:


 void copyKeyFieldsFromObjectId
 
        (ObjectIdFieldConsumer fm, Object objectId) {
 
     EmployeeKey oid = (EmployeeKey)objectId;
 
     fm.storeIntField (0, oid.id);
 
     fm.storeStringField (1, oid.name);
 
     fm.storeObjectField (2, oid.salary);

}

The implementation is responsible for implementing the ObjectIdFieldConsumer to store the values for the key fields.

Parameters:: oid - the ObjectId source of the copy.; fm - the field manager that receives the field values.

Since:: JDO 1.0

Copy fields from this PersistenceCapable instance to the Object Id instance.

For classes using single field identity, this method always throws JDOUserException.

Parameters:: oid - the ObjectId target of the key fields

Since:: JDO 1.0

Copy fields from an outside source to the key fields in the ObjectId.

This method is generated in the PersistenceCapable class to generate a call to the field manager for each key field in the ObjectId. For example, an ObjectId class that has three key fields

(int id,
 String name, and Float salary)

would have the method generated:


 void jdoCopyKeyFieldsToObjectId
 
(ObjectIdFieldSupplier fm, Object objectId) {
 
EmployeeKey oid = (EmployeeKey)objectId;
 
oid.id = fm.fetchIntField (0);
 
oid.name = fm.fetchStringField (1);
 
oid.salary = fm.fetchObjectField (2);

}

The implementation is responsible for implementing the ObjectIdFieldSupplier to produce the values for the key fields.

For classes using single field identity, this method always throws JDOUserException.

Parameters:: oid - the ObjectId target of the copy.; fm - the field supplier that supplies the field values.

Since:: JDO 1.0

Return a copy of the JDO identity associated with this instance.

Persistent instances of PersistenceCapable classes have a JDO identity managed by the PersistenceManager. This method returns a copy of the ObjectId that represents the JDO identity.

Transient instances return null.

The ObjectId may be serialized and later restored, and used with a PersistenceManager from the same JDO implementation to locate a persistent instance with the same data store identity.

If the JDO identity is managed by the application, then the ObjectId may be used with a PersistenceManager from any JDO implementation that supports the PersistenceCapable class.

If the JDO identity is not managed by the application or the data store, then the ObjectId returned is only valid within the current transaction.

If the JDO identity is being changed in the transaction, this method returns the object id as of the beginning of the current transaction.

Return:: a copy of the ObjectId of this instance as of the beginning of the transaction.

See Also:: PersistenceManager.getObjectId(Object pc); PersistenceManager.getObjectById(Object oid,boolean validate)

Since:: JDO 1.0

Return the associated PersistenceManager if there is one.

Transactional and persistent instances return the associated PersistenceManager.

Transient non-transactional instances return null.

This method always delegates to the StateManager if it is non-null.

Return:: the PersistenceManager associated with this instance.

Since:: JDO 1.0

Return a copy of the JDO identity associated with this instance.

This method is the same as jdoGetObjectId if the identity of the instance has not changed in the current transaction.

If the JDO identity is being changed in the transaction, this method returns the current object id as modified in the current transaction.

Return:: a copy of the ObjectId of this instance as modified in the transaction.

See Also:: jdoGetObjectId(); PersistenceManager.getObjectId(Object pc); PersistenceManager.getObjectById(Object oid,boolean validate)

Since:: JDO 1.0

Return the version of this instance.

Return:: the version

Since:: JDO 2.0

Tests whether this object has been deleted.

Instances that have been deleted in the current transaction return true.

Transient instances return false.

Return:: true if this instance was deleted in the current transaction.

See Also:: javax.jdo.JDOHelper.isDeleted(Object pc); PersistenceManager.deletePersistent(Object pc)

Since:: JDO 1.0

Tests whether this object has been detached.

Instances that have been detached return true.

Transient instances return false.

Return:: true if this instance is detached.

See Also:: javax.jdo.JDOHelper.isDetached(Object pc)

Since:: JDO 2.0

Tests whether this object is dirty.

Instances that have been modified, deleted, or newly made persistent in the current transaction return true.

Transient instances return false.

Return:: true if this instance has been modified in the current transaction.

See Also:: javax.jdo.JDOHelper.isDirty(Object pc); javax.jdo.JDOHelper.makeDirty(Object pc,String fieldName); jdoMakeDirty(String fieldName)

Since:: JDO 1.0

Tests whether this object has been newly made persistent.

Instances that have been made persistent in the current transaction return true.

Transient instances return false.

Return:: true if this instance was made persistent in the current transaction.

See Also:: javax.jdo.JDOHelper.isNew(Object pc); PersistenceManager.makePersistent(Object pc)

Since:: JDO 1.0

Tests whether this object is persistent.

Instances that represent persistent objects in the data store return true.

Return:: true if this instance is persistent.

See Also:: javax.jdo.JDOHelper.isPersistent(Object pc); PersistenceManager.makePersistent(Object pc)

Since:: JDO 1.0

Tests whether this object is transactional.

Instances whose state is associated with the current transaction return true.

Transient instances return false.

Return:: true if this instance is transactional.

See Also:: javax.jdo.JDOHelper.isTransactional(Object pc); PersistenceManager.makeTransactional(Object pc)

Since:: JDO 1.0

Explicitly mark this instance and this field dirty.

Normally, PersistenceCapable classes are able to detect changes made to their fields. However, if a reference to an array is given to a method outside the class, and the array is modified, then the persistent instance is not aware of the change. This API allows the application to notify the instance that a change was made to a field.

The field name should be the fully qualified name, including package name and class name of the class declaring the field. This allows unambiguous identification of the field to be marked dirty. If multiple classes declare the same field, and if the package and class name are not provided by the parameter in this API, then the field marked dirty is the field declared by the most derived class.

Transient instances ignore this method.

Parameters:: fieldName - the name of the field to be marked dirty.

Since:: JDO 1.0

Return a new instance of this class, with the jdoStateManager set to the parameter, and jdoFlags set to LOAD_REQUIRED.

This method is used as a performance optimization as an alternative to using reflection to construct a new instance. It is used by the JDOImplHelper class method newInstance.

Parameters:: sm - the StateManager that will own the new instance.

Return:: a new instance of this class.

See Also:: JDOImplHelper.newInstance(Class pcClass,StateManager sm)

Since:: JDO 1.0

Return a new instance of this class, with the jdoStateManager set to the parameter, key fields initialized to the values in the oid, and jdoFlags set to LOAD_REQUIRED.

This method is used as a performance optimization as an alternative to using reflection to construct a new instance of a class that uses application identity. It is used by the JDOImplHelper class method newInstance.

Parameters:: sm - the StateManager that will own the new instance.; oid - an instance of the object id class (application identity).

Return:: a new instance of this class.

See Also:: JDOImplHelper.newInstance(Class pcClass,StateManager sm)

Since:: JDO 1.0

Create a new instance of the ObjectId class for this PersistenceCapable class and initialize the key fields from the instance on which this method is called.

This method creates a new instance of the class used for JDO identity. It is intended only for application identity. If the class has been enhanced for datastore identity, or if the class is abstract, null is returned.

For classes using single field identity, this method must be called on an instance of a persistence-capable class with its primary key field initialized (not null), or a JDONullIdentityException is thrown.

The instance returned is initialized with the value(s) of the primary key field(s) of the instance on which the method is called.

Return:: the new instance created.

Since:: JDO 1.0

Create a new instance of the class used for JDO identity, using the key constructor of the object id class.

It is intended for single field identity. The identity instance returned has no relationship with the values of the primary key fields of the persistence-capable instance on which the method is called. If the key is the wrong class for the object id class, null is returned.

For classes that use single field identity, if the parameter is of one of the following types, the behavior must be as specified:

Number or Character: the parameter must be the single field type or the wrapper class of the primitive field type; the parameter is passed to the single field identity constructor
ObjectIdFieldSupplier: the field value is fetched from the ObjectIdFieldSupplier and passed to the single field identity constructor
String: the String is passed to the single field identity constructor

Parameters:: o - the object identity constructor parameter

Return:: the new instance created.

Since:: JDO 2.0

The owning StateManager uses this method to ask the instance to provide the value of the single field identified by fieldNumber.

Parameters:: fieldNumber - the field whose value is to be provided by a callback to the StateManager's providedXXXField method

Since:: JDO 1.0

The owning StateManager uses this method to ask the instance to provide the values of the multiple fields identified by fieldNumbers.

Parameters:: fieldNumbers - the fields whose values are to be provided by multiple callbacks to the StateManager's providedXXXField method

Since:: JDO 1.0

The owning StateManager uses this method to ask the instance to replace the value of the single field identified by number.

Parameters:: fieldNumber - the field whose value is to be replaced by a callback to the StateManager's replacingXXXField method

Since:: JDO 1.0

The owning StateManager uses this method to ask the instance to replace the values of the multiple fields identified by number.

Parameters:: fieldNumbers - the fields whose values are to be replaced by multiple callbacks to the StateManager's replacingXXXField method

Since:: JDO 1.0

The owning StateManager uses this method to ask the instance to replace the value of the flags by calling back the StateManager replacingFlags method.

Since:: JDO 1.0

This method sets the StateManager instance that manages the state of this instance.

This method is normally used by the StateManager during the process of making an instance persistent, transient, or transactional. The caller of this method must have JDOPermission for the instance, if the instance is not already owned by a StateManager. If the parameter is null, and the StateManager approves the change, then the jdoFlags field will be reset to READ_WRITE_OK. If the parameter is not null, and the security manager approves the change, then the jdoFlags field will be reset to LOAD_REQUIRED.

Parameters:: sm - The StateManager which will own this instance, or null to reset the instance to transient state

Throws:: SecurityExceptionif the caller does not have JDOPermission

See Also:: JDOPermission

Since:: JDO 1.0