Package org.datanucleus.enhancement

Interface Persistable

  • public interface Persistable
    A class that can be managed by DataNucleus must implement this interface.

    This interface defines methods that allow the implementation to manage the instances. It also defines methods that allow a DataNucleus 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 ExecutionContext, object identity, and version if it has one.

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

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static byte CHECK_READ
      dnFieldFlags for a field includes CHECK_READ, then the field has been enhanced to call the StateManager on read if the dnFlags setting is not READ_OK or READ_WRITE_OK
      static byte CHECK_WRITE
      dnFieldFlags for a field includes CHECK_WRITE, then the field has been enhanced to call the StateManager on write if the dnFlags setting is not READ_WRITE_OK
      static byte LOAD_REQUIRED
      dnFlags == LOAD_REQUIRED, then the fields in the default fetch group cannot be accessed for read or write without notifying the StateManager.
      static byte MEDIATE_READ
      dnFieldFlags for a field includes MEDIATE_READ, then the field has been enhanced to always call the StateManager on all reads
      static byte MEDIATE_WRITE
      dnFieldFlags for a field includes MEDIATE_WRITE, then the field has been enhanced to always call the StateManager on all writes
      static byte READ_OK
      dnFlags == READ_OK, then the fields in the default fetch group can be accessed for read without notifying the StateManager
      static byte READ_WRITE_OK
      dnFlags == READ_WRITE_OK, then the fields in the default fetch group can be accessed for read or write without notifying the StateManager.
      static byte SERIALIZABLE
      dnFieldFlags for a field includes SERIALIZABLE, then the field is not declared as TRANSIENT.

    • Field Detail

      • READ_WRITE_OK

        static final byte READ_WRITE_OK
        dnFlags == READ_WRITE_OK, then the fields in the default fetch group can be accessed for read or write without notifying the StateManager.
        See Also:
        Constant Field Values

      • LOAD_REQUIRED

        static final byte LOAD_REQUIRED
        dnFlags == LOAD_REQUIRED, then the fields in the default fetch group cannot be accessed for read or write without notifying the StateManager.
        See Also:
        Constant Field Values

      • READ_OK

        static final byte READ_OK
        dnFlags == READ_OK, then the fields in the default fetch group can be accessed for read without notifying the StateManager
        See Also:
        Constant Field Values

      • CHECK_READ

        static final byte CHECK_READ
        dnFieldFlags for a field includes CHECK_READ, then the field has been enhanced to call the StateManager on read if the dnFlags setting is not READ_OK or READ_WRITE_OK
        See Also:
        Constant Field Values

      • MEDIATE_READ

        static final byte MEDIATE_READ
        dnFieldFlags for a field includes MEDIATE_READ, then the field has been enhanced to always call the StateManager on all reads
        See Also:
        Constant Field Values

      • CHECK_WRITE

        static final byte CHECK_WRITE
        dnFieldFlags for a field includes CHECK_WRITE, then the field has been enhanced to call the StateManager on write if the dnFlags setting is not READ_WRITE_OK
        See Also:
        Constant Field Values

      • MEDIATE_WRITE

        static final byte MEDIATE_WRITE
        dnFieldFlags for a field includes MEDIATE_WRITE, then the field has been enhanced to always call the StateManager on all writes
        See Also:
        Constant Field Values

      • SERIALIZABLE

        static final byte SERIALIZABLE
        dnFieldFlags for a field includes SERIALIZABLE, then the field is not declared as TRANSIENT.
        See Also:
        Constant Field Values

    • Method Detail

      • dnGetExecutionContext

        ExecutionContextReference dnGetExecutionContext()
        Return the associated ExecutionContext if there is one. Transactional and persistent instances return the associated ExecutionContext. Transient non-transactional instances return null. This method always delegates to the StateManager if it is non-null.
        Returns:
        the ExecutionContext associated with this instance.

      • dnGetStateManager

        StateManager dnGetStateManager()
        Return the associated StateManager if there is one.
        Returns:
        The StateManager managing this object

      • dnReplaceStateManager

        void dnReplaceStateManager​(StateManager sm)
                    throws SecurityException
        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 dnFlags field will be reset to READ_WRITE_OK. If the parameter is not null, and the security manager approves the change, then the dnFlags 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:
        SecurityException - if the caller does not have JDOPermission

      • dnProvideField

        void dnProvideField​(int fieldNumber)
        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

      • dnProvideFields

        void dnProvideFields​(int[] fieldNumbers)
        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

      • dnReplaceField

        void dnReplaceField​(int fieldNumber)
        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

      • dnReplaceFields

        void dnReplaceFields​(int[] fieldNumbers)
        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

      • dnReplaceFlags

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

      • dnCopyFields

        void dnCopyFields​(Object other,
                  int[] fieldNumbers)
        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

      • dnMakeDirty

        void dnMakeDirty​(String fieldName)
        Explicitly mark this instance and this field dirty. Normally, Persistable 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.

      • dnGetObjectId

        Object dnGetObjectId()
        Return a copy of the identity associated with this instance.

        Persistent instances of Persistable classes have an identity managed by the ExecutionContext. This method returns a copy of the ObjectId that represents the identity.

        Transient instances return null.

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

        If the identity is managed by the application, then the ObjectId may be used with a ExecutionContext from DataNucleus that supports the Persistable class.

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

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

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

      • dnGetTransactionalObjectId

        Object dnGetTransactionalObjectId()
        Return a copy of the identity associated with this instance. This method is the same as dnGetObjectId if the identity of the instance has not changed in the current transaction.

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

        Returns:
        a copy of the ObjectId of this instance as modified in the transaction.
        See Also:
        dnGetObjectId()

      • dnGetVersion

        Object dnGetVersion()
        Return the version of this instance.
        Returns:
        the version

      • dnIsDirty

        boolean dnIsDirty()
        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. Embedded instances return false.

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

      • dnIsTransactional

        boolean dnIsTransactional()
        Tests whether this object is transactional. Instances whose state is associated with the current transaction return true. Transient instances return false.
        Returns:
        true if this instance is transactional.

      • dnIsPersistent

        boolean dnIsPersistent()
        Tests whether this object is persistent. Instances that represent persistent objects in the data store return true.
        Returns:
        true if this instance is persistent.

      • dnIsNew

        boolean dnIsNew()
        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.
        Returns:
        true if this instance was made persistent in the current transaction.

      • dnIsDeleted

        boolean dnIsDeleted()
        Tests whether this object has been deleted. Instances that have been deleted in the current transaction return true. Transient instances return false.
        Returns:
        true if this instance was deleted in the current transaction.

      • dnIsDetached

        boolean dnIsDetached()
        Tests whether this object has been detached. Instances that have been detached return true. Transient instances return false.
        Returns:
        true if this instance is detached.

      • dnNewInstance

        Persistable dnNewInstance​(StateManager sm)
        Return a new instance of this class, with the StateManager set to the parameter, and dnFlags set to LOAD_REQUIRED.

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

        Parameters:
        sm - the StateManager that will own the new instance.
        Returns:
        a new instance of this class.

      • dnNewInstance

        Persistable dnNewInstance​(StateManager sm,
                          Object oid)
        Return a new instance of this class, with the StateManager set to the parameter, key fields initialised to the values in the oid, and dnFlags set to LOAD_REQUIRED.

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

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

      • dnNewObjectIdInstance

        Object dnNewObjectIdInstance()
        Create a new instance of the ObjectId class for this Persistable 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 identity. It is intended only for application identity. If the class uses 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 initialised (not null), or an exception 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.

        Returns:
        the new instance created.

      • dnNewObjectIdInstance

        Object dnNewObjectIdInstance​(Object o)
        Create a new instance of the class used for 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 behaviour 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
        Returns:
        the new instance created.

      • dnCopyKeyFieldsToObjectId

        void dnCopyKeyFieldsToObjectId​(Object oid)
        Copy fields from this Persistable 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

      • dnCopyKeyFieldsToObjectId

        void dnCopyKeyFieldsToObjectId​(Persistable.ObjectIdFieldSupplier fm,
                               Object oid)
        Copy fields from an outside source to the key fields in the ObjectId. This method is generated in the Persistable 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 dnCopyKeyFieldsToObjectId(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.

      • dnCopyKeyFieldsFromObjectId

        void dnCopyKeyFieldsFromObjectId​(Persistable.ObjectIdFieldConsumer fm,
                                 Object oid)
        Copy fields to an outside consumer from the key fields in the ObjectId. This method is generated in the Persistable 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.