javax.jdo.spi
Class JDOImplHelper

java.lang.Object
  |
  +--javax.jdo.spi.JDOImplHelper

public class JDOImplHelper

extends java.lang.Object

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.

Version:

0.9

Author:

Craig Russell

Method Summary

void	addRegisterClassListener(RegisterClassListener crl) Add the specified RegisterClassListener to the listener list.
static void	checkAuthorizedStateManager(StateManager sm) Check that the parameter instance is of a class that is authorized for JDOPermission("setStateManager").
static void	checkAuthorizedStateManagerClass(java.lang.Class smClass) Check that the parameter instance is a class that is authorized for JDOPermission("setStateManager").
void	copyKeyFieldsFromObjectId(java.lang.Class pcClass, PersistenceCapable.ObjectIdFieldConsumer fm, java.lang.Object oid) Copy fields to an outside source from the key fields in the ObjectId.
void	copyKeyFieldsToObjectId(java.lang.Class pcClass, PersistenceCapable.ObjectIdFieldSupplier fm, java.lang.Object oid) Copy fields from an outside source to the key fields in the ObjectId.
byte[]	getFieldFlags(java.lang.Class pcClass) Get the field flags for a PersistenceCapable class.
java.lang.String[]	getFieldNames(java.lang.Class pcClass) Get the field names for a PersistenceCapable class.
java.lang.Class[]	getFieldTypes(java.lang.Class pcClass) Get the field types for a PersistenceCapable class.
static JDOImplHelper	getInstance() Get an instance of JDOImplHelper.
java.lang.Class	getPersistenceCapableSuperclass(java.lang.Class pcClass) Get the persistence-capable superclass for a PersistenceCapable class.
java.util.Collection	getRegisteredClasses() Returns a collection of class objects of the registered persistence-capable classes.
PersistenceCapable	newInstance(java.lang.Class pcClass, StateManager sm) Create a new instance of the class and assign its jdoStateManager.
PersistenceCapable	newInstance(java.lang.Class pcClass, StateManager sm, java.lang.Object oid) Create a new instance of the class and assign its jdoStateManager and key values from the ObjectId.
java.lang.Object	newObjectIdInstance(java.lang.Class pcClass) Create a new instance of the ObjectId class of this PersistenceCapable class.
java.lang.Object	newObjectIdInstance(java.lang.Class pcClass, java.lang.String str) Create a new instance of the ObjectId class of this PersistenceCapable class, using the String form of the constructor.
static void	registerAuthorizedStateManagerClass(java.lang.Class smClass) Register a class authorized to replaceStateManager.
static void	registerAuthorizedStateManagerClasses(java.util.Collection smClasses) Register classes authorized to replaceStateManager.
static void	registerClass(java.lang.Class pcClass, java.lang.String[] fieldNames, java.lang.Class[] fieldTypes, byte[] fieldFlags, java.lang.Class persistenceCapableSuperclass, PersistenceCapable pc) Register metadata by class.
void	removeRegisterClassListener(RegisterClassListener crl) Remove the specified RegisterClassListener from the listener list.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getInstance

public static JDOImplHelper getInstance()
                                 throws java.lang.SecurityException

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:

java.lang.SecurityException - if the caller is not authorized for JDOPermission("getMetadata").

getFieldNames

public java.lang.String[] getFieldNames(java.lang.Class pcClass)

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.

getFieldTypes

public java.lang.Class[] getFieldTypes(java.lang.Class pcClass)

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.

getFieldFlags

public byte[] getFieldFlags(java.lang.Class pcClass)

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.

getPersistenceCapableSuperclass

public java.lang.Class getPersistenceCapableSuperclass(java.lang.Class pcClass)

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.

newInstance

public PersistenceCapable newInstance(java.lang.Class pcClass,
                                      StateManager sm)

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.

See Also:

PersistenceCapable.jdoNewInstance(StateManager sm)

newInstance

public PersistenceCapable newInstance(java.lang.Class pcClass,
                                      StateManager sm,
                                      java.lang.Object oid)

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.

See Also:

PersistenceCapable.jdoNewInstance(StateManager sm, Object oid)

newObjectIdInstance

public java.lang.Object newObjectIdInstance(java.lang.Class pcClass)

Create a new instance of the ObjectId class of this PersistenceCapable class.

Parameters:

pcClass - the PersistenceCapable class.

Returns:

the new ObjectId instance, or null if the class is not registered.

newObjectIdInstance

public java.lang.Object newObjectIdInstance(java.lang.Class pcClass,
                                            java.lang.String str)

Create a new instance of the ObjectId class of this PersistenceCapable class, using the String form of the constructor.

Parameters:

str - the String form of the object id

pcClass - the PersistenceCapable class.

Returns:

the new ObjectId instance, or null if the class is not registered.

copyKeyFieldsToObjectId

public void copyKeyFieldsToObjectId(java.lang.Class pcClass,
                                    PersistenceCapable.ObjectIdFieldSupplier fm,
                                    java.lang.Object oid)

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.

oid - the ObjectId target of the copy.

fm - the field manager that supplies the field values.

copyKeyFieldsFromObjectId

public void copyKeyFieldsFromObjectId(java.lang.Class pcClass,
                                      PersistenceCapable.ObjectIdFieldConsumer fm,
                                      java.lang.Object oid)

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

oid - the ObjectId source of the copy.

fm - the field manager that receives the field values.

registerClass

public static void registerClass(java.lang.Class pcClass,
                                 java.lang.String[] fieldNames,
                                 java.lang.Class[] fieldTypes,
                                 byte[] fieldFlags,
                                 java.lang.Class persistenceCapableSuperclass,
                                 PersistenceCapable pc)

Register metadata by class. The registration will be done in the class named JDOImplHelper loaded by the same 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

pc - an instance of the PersistenceCapable class

persistenceCapableSuperclass - the most immediate superclass that is PersistenceCapable

addRegisterClassListener

public void addRegisterClassListener(RegisterClassListener crl)

Add the specified RegisterClassListener to the listener list.

Parameters:

crl - the listener to be added

removeRegisterClassListener

public void removeRegisterClassListener(RegisterClassListener crl)

Remove the specified RegisterClassListener from the listener list.

Parameters:

crl - the listener to be removed

getRegisteredClasses

public java.util.Collection getRegisteredClasses()

Returns a collection of class objects of the registered persistence-capable classes.

Returns:

registered persistence-capable classes

registerAuthorizedStateManagerClass

public static void registerAuthorizedStateManagerClass(java.lang.Class smClass)
                                                throws java.lang.SecurityException

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:

java.lang.SecurityException - if the caller is not authorized for JDOPermission("setStateManager").

registerAuthorizedStateManagerClasses

public static void registerAuthorizedStateManagerClasses(java.util.Collection smClasses)
                                                  throws java.lang.SecurityException

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:

java.lang.SecurityException - if the caller is not authorized for JDOPermission("setStateManager").

checkAuthorizedStateManager

public static void checkAuthorizedStateManager(StateManager sm)

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.

checkAuthorizedStateManagerClass

public static void checkAuthorizedStateManagerClass(java.lang.Class smClass)

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")