javax.jdo.spi.JDOImplHelper - JDO class

javax.jdo.spi
Class JDOImplHelper

java.lang.Object
    javax.jdo.spi.JDOImplHelper
This class is a helper class for JDO implementations. It contains methods to register metadata for persistence-capable classes and to perform common operations needed by implementations, not by end users.

JDOImplHelper allows construction of instances of persistence-capable classes without using reflection.

Persistence-capable classes register themselves via a static method at class load time. There is no security restriction on this access. JDO implementations get access to the functions provided by this class only if they are authorized by the security manager. To avoid having every call go through the security manager, only the call to get an instance is checked. Once an implementation has an instance, any of the methods can be invoked without security checks.

Since:
JDO 1.0
Check that the parameter instance is of a class that is authorized for JDOPermission("setStateManager").
Check that the parameter instance is of a class that is authorized for JDOPermission("setStateManager"). This method is called by the replaceStateManager method in persistence-capable classes. A class that is passed as the parameter to replaceStateManager must be authorized for JDOPermission("setStateManager"). To improve performance, first the set of authorized classes is checked, and if not present, a regular permission check is made. The regular permission check requires that all callers on the stack, including the persistence-capable class itself, must be authorized for JDOPermission("setStateManager").
Parameters:
sm - an instance of StateManager whose class is to be checked.
Since:
JDO 1.0.1
void checkAuthorizedStateManagerClass(Class smClass)
Check that the parameter instance is a class that is authorized for JDOPermission("setStateManager").
Check that the parameter instance is a class that is authorized for JDOPermission("setStateManager"). This method is called by the constructors of JDO Reference Implementation classes.
Parameters:
smClass - a Class to be checked for JDOPermission("setStateManager")
Since:
JDO 1.0.1
Object construct(String className, String keyString)
Construct an instance of the parameter class, using the keyString as an argument to the constructor.
Construct an instance of the parameter class, using the keyString as an argument to the constructor. If the class has a StringConstructor instance registered, use it. If not, try to find a constructor for the class with a single String argument. Otherwise, throw a JDOUserException.
Parameters:
className - the name of the class
keyString - the String parameter for the constructor
Returns:
the result of construction
Since:
JDO 1.0
Get an instance of JDOImplHelper.
Get an instance of JDOImplHelper. This method checks that the caller is authorized for JDOPermission("getMetadata"), and if not, throws SecurityException.
Returns:
an instance of JDOImplHelper.
Throws:
SecurityException - if the caller is not authorized for JDOPermission("getMetadata").
Since:
JDO 1.0
DocumentBuilderFactory getRegisteredDocumentBuilderFactory()
Return the registered instance of DocumentBuilderFactory.
Return the registered instance of DocumentBuilderFactory.
Returns:
the DocumentBuilderFactory if registered; null otherwise
Since:
JDO 2.1
ErrorHandler getRegisteredErrorHandler()
Return the registered instance of ErrorHandler.
Return the registered instance of ErrorHandler.
Returns:
the registered ErrorHandler if registered; null otherwise
Since:
JDO 2.1
Register a class authorized to replaceStateManager.
Register a class authorized to replaceStateManager. The caller of this method must be authorized for JDOPermission("setStateManager"). During replaceStateManager, a persistence-capable class will call the corresponding checkAuthorizedStateManager and the class of the instance of the parameter must have been registered.
Parameters:
smClass - a Class that is authorized for JDOPermission("setStateManager").
Throws:
SecurityException - if the caller is not authorized for JDOPermission("setStateManager").
Since:
JDO 1.0.1
void registerAuthorizedStateManagerClasses(Collection smClasses)
Register classes authorized to replaceStateManager.
Register classes authorized to replaceStateManager. The caller of this method must be authorized for JDOPermission("setStateManager"). During replaceStateManager, a persistence-capable class will call the corresponding checkAuthorizedStateManager and the class of the instance of the parameter must have been registered.
Parameters:
smClasses - a Collection of Classes that are authorized for JDOPermission("setStateManager").
Throws:
SecurityException - if the caller is not authorized for JDOPermission("setStateManager").
Since:
JDO 1.0.1
void registerClass(Class pcClass, String[] fieldNames, Class[] fieldTypes, byte[] fieldFlags, Class persistenceCapableSuperclass, PersistenceCapable pc)
Register metadata by class.
Register metadata by class. The registration will be done in the class named JDOImplHelper loaded by the same or an ancestor class loader as the PersistenceCapable class performing the registration.
Parameters:
pcClass - the PersistenceCapable class used as the key for lookup.
fieldNames - an array of String field names for persistent and transactional fields
fieldTypes - an array of Class field types
fieldFlags - the Field Flags for persistent and transactional fields
persistenceCapableSuperclass - the most immediate superclass that is PersistenceCapable
pc - an instance of the PersistenceCapable class
Since:
JDO 1.0
Add the specified RegisterClassListener to the listener list.
Add the specified RegisterClassListener to the listener list.
Parameters:
crl - the listener to be added
Since:
JDO 1.0
Add a StateInterrogation to the list.
Add a StateInterrogation to the list. Create a new list in case there is an iterator open on the original list.
Parameters:
si - the StateInterrogation to add
Since:
JDO 1.0
void copyKeyFieldsFromObjectId(Class pcClass, ObjectIdFieldConsumer fm, Object oid)
Copy fields to an outside source from the key fields in the ObjectId.
Copy fields to an outside source 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 jdoCopyKeyFieldsFromObjectId
(PersistenceCapable oid, ObjectIdFieldConsumer fm) {
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:
pcClass - the PersistenceCapable class
fm - the field manager that receives the field values.
oid - the ObjectId source of the copy.
Since:
JDO 1.0
void copyKeyFieldsToObjectId(Class pcClass, ObjectIdFieldSupplier fm, Object oid)
Copy fields from an outside source to the key fields in the ObjectId.
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 (Object oid, ObjectIdFieldSupplier fm) {
oid.id = fm.fetchIntField (0);
oid.name = fm.fetchStringField (1);
oid.salary = fm.fetchObjectField (2);
}

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

Parameters:
pcClass - the PersistenceCapable Class.
fm - the field manager that supplies the field values.
oid - the ObjectId target of the copy.
Since:
JDO 1.0
byte[] getFieldFlags(Class pcClass)
Get the field flags for a PersistenceCapable class.
Get the field flags for a PersistenceCapable class. The order of fields is the same as for field names.
Parameters:
pcClass - the PersistenceCapable class.
Returns:
the field types for the class.
Since:
JDO 1.0
String[] getFieldNames(Class pcClass)
Get the field names for a PersistenceCapable class.
Get the field names for a PersistenceCapable class. The order of fields is the natural ordering of the String class (without considering localization).
Parameters:
pcClass - the PersistenceCapable class.
Returns:
the field names for the class.
Since:
JDO 1.0
Class[] getFieldTypes(Class pcClass)
Get the field types for a PersistenceCapable class.
Get the field types for a PersistenceCapable class. The order of fields is the same as for field names.
Parameters:
pcClass - the PersistenceCapable class.
Returns:
the field types for the class.
Since:
JDO 1.0
Class getPersistenceCapableSuperclass(Class pcClass)
Get the persistence-capable superclass for a PersistenceCapable class.
Get the persistence-capable superclass for a PersistenceCapable class.
Parameters:
pcClass - the PersistenceCapable class.
Returns:
The PersistenceCapable superclass for this class, or null if there isn't one.
Since:
JDO 1.0
Collection getRegisteredClasses()
Returns a collection of class objects of the registered persistence-capable classes.
Returns a collection of class objects of the registered persistence-capable classes.
Returns:
registered persistence-capable classes
Since:
JDO 1.0
Create a new instance of the class and assign its jdoStateManager.
Create a new instance of the class and assign its jdoStateManager. The new instance has its jdoFlags set to LOAD_REQUIRED.
Parameters:
pcClass - the PersistenceCapable class.
sm - the StateManager which will own the new instance.
Returns:
the new instance, or null if the class is not registered.
Since:
JDO 1.0
See Also:
PersistenceCapable.jdoNewInstance(StateManager sm)
PersistenceCapable newInstance(Class pcClass, StateManager sm, Object oid)
Create a new instance of the class and assign its jdoStateManager and key values from the ObjectId.
Create a new instance of the class and assign its jdoStateManager and key values from the ObjectId. If the oid parameter is null, no key values are copied. The new instance has its jdoFlags set to LOAD_REQUIRED.
Parameters:
pcClass - the PersistenceCapable class.
sm - the StateManager which will own the new instance.
oid - the ObjectId instance from which to copy key field values.
Returns:
the new instance, or null if the class is not registered.
Since:
JDO 1.0
See Also:
PersistenceCapable.jdoNewInstance(StateManager sm, Object oid)
Object newObjectIdInstance(Class pcClass)
Create a new instance of the ObjectId class of this PersistenceCapable class.
Create a new instance of the ObjectId class of this PersistenceCapable class. It is intended only for application identity. This method should not be called for classes that use single field identity; newObjectIdInstance(Class, Object) should be used instead. If the class has been enhanced for datastore identity, or if the class is abstract, null is returned.
Parameters:
pcClass - the PersistenceCapable class.
Returns:
the new ObjectId instance, or null if the class is not registered.
Since:
JDO 1.0
Object newObjectIdInstance(Class pcClass, Object obj)
Create a new instance of the class used by the parameter Class for JDO identity, using the key constructor of the object id class.
Create a new instance of the class used by the parameter Class 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:
pcClass - the PersistenceCapable class.
obj - the Object form of the object id
Returns:
the new ObjectId instance, or null if the class is not registered.
Since:
JDO 2.0
Return an object associated with a non-binary-compatible instance.
Return an object associated with a non-binary-compatible instance. Delegate to all registered StateInterrogation instances until one of them handles the call (returns a non-null answer). The caller provides the stateless "method object" that does the actual call to the StateInterrogation instance.
Parameters:
pc - the instance whose associated object is needed
sibr - the method object that delegates to the non-binary-compatible implementation
Returns:
the associated object or null if the implementation does not manage the class of the instance
Since:
JDO 1.0
Determine the state of a non-binary-compatible instance.
Determine the state of a non-binary-compatible instance. Delegate to all registered StateInterrogation instances until one of them handles the call (returns a non-null Boolean with the answer). The caller provides the stateless "method object" that does the actual call to the StateInterrogation instance.
Parameters:
pc - the instance to be checked
sibr - the method object that delegates to the non-binary-compatible implementation
Returns:
Boolean.TRUE if the instance satisfies the state interrogation; Boolean.FALSE if the instance does not satisfy the interrogation; or null if the implementation does not manage the class of the instance
Since:
JDO 1.0
void nonBinaryCompatibleMakeDirty(Object pc, String fieldName)
Mark a non-binary-compatible instance dirty.
Mark a non-binary-compatible instance dirty. Delegate to all registered StateInterrogation instances until one of them handles the call.
Parameters:
pc - the instance to mark dirty
fieldName - the field to mark dirty
Since:
JDO 1.0
void registerDateFormat(DateFormat df)
Register a DateFormat instance for use with constructing Date instances.
Register a DateFormat instance for use with constructing Date instances. The default is the default DateFormat instance. If the new instance implements SimpleDateFormat, get its pattern for error messages.
Parameters:
df - the DateFormat instance to use
Since:
JDO 2.0
void registerDocumentBuilderFactory(DocumentBuilderFactory factory)
Register a DocumentBuilderFactory instance for use in parsing the resource(s) META-INF/jdoconfig.xml.
Register a DocumentBuilderFactory instance for use in parsing the resource(s) META-INF/jdoconfig.xml. The default is governed by the semantics of DocumentBuilderFactory.newInstance().
Parameters:
factory - the DocumentBuilderFactory instance to use
Since:
JDO 2.1
void registerErrorHandler(ErrorHandler handler)
Register an ErrorHandler instance for use in parsing the resource(s) META-INF/jdoconfig.xml.
Register an ErrorHandler instance for use in parsing the resource(s) META-INF/jdoconfig.xml. The default is an ErrorHandler that throws on error or fatalError and ignores warnings.
Parameters:
handler - the ErrorHandler instance to use
Since:
JDO 2.1
Register special StringConstructor instances.
Register special StringConstructor instances. These instances are for constructing instances from String parameters where there is no String constructor for them.
Parameters:
cls - the class to register a StringConstructor for
sc - the StringConstructor instance
Returns:
the previous StringConstructor registered for this class
Since:
JDO 1.0
Remove the specified RegisterClassListener from the listener list.
Remove the specified RegisterClassListener from the listener list.
Parameters:
crl - the listener to be removed
Since:
JDO 1.0
Remove a StateInterrogation from the list.
Remove a StateInterrogation from the list. Create a new list in case there is an iterator open on the original list.
Parameters:
si - the StateInterrogation to remove
Since:
JDO 1.0
void unregisterClass(Class pcClass)
Unregister metadata by class.
Unregister metadata by class. This method unregisters the specified class. Any further attempt to get metadata for the specified class will result in a JDOFatalUserException.
Parameters:
pcClass - the PersistenceCapable class to be unregistered.
Since:
JDO 1.0.2
void unregisterClasses(ClassLoader cl)
Unregister metadata by class loader.
Unregister metadata by class loader. This method unregisters all registered PersistenceCapable classes loaded by the specified class loader. Any attempt to get metadata for unregistered classes will result in a JDOFatalUserException.
Parameters:
cl - the class loader.
Since:
JDO 1.0.2

This documentation page is derived (with some adjustments) from the JDO 2.2 API
and is available under the terms of the Apache License, v. 2.0.