org.jpox
Class JDOClassLoaderResolver

java.lang.Object
  org.jpox.JDOClassLoaderResolver

All Implemented Interfaces:

ClassLoaderResolver

public class JDOClassLoaderResolver
extends java.lang.Object
implements ClassLoaderResolver

A basic implementation of a ClassLoaderResolver for JDO. A ClassLoaderResolver provides a series of methods for resolving classes from their names. It supports up to 3 class loaders.

JDO2 Spec section 12.5

The class loaders will be used in this order:

1. The loader that loaded the class or instance referred to in the API that caused this class to be loaded.
• In case of query, this is the loader of the candidate class, or the loader of the object passed to the newQuery
• In case of navigation from a persistent instance, this is the loader of the class of the instance.
• In the case of getExtent with subclasses, this is the loader of the candidate class.
• In the case of getObjectById, this is the loader of the object id instance.
• Other cases do not have an explicit loader.
2. The loader returned in the current context by Thread.getContextClassLoader().
3. The loader returned by Thread.getContextClassLoader() at the time of PersistenceManagerFactory.getPersistenceManager().
4. The loader registered for dynamically creating and loading classes at runtime.

Version:

$Revision: 1.21 $

Field Summary

protected java.util.Map	loadedClasses Cache for loaded classes
protected static Localiser	LOCALISER Localisation utility for output messages
protected java.lang.ClassLoader	pmContextLoader ClassLoader initialised by the PM creation.
protected int	pmContextLoaderHashCode Hash code cache for performance improvement
protected java.lang.ClassLoader	registeredLoader ClassLoader registered to load runtime created classes.
protected int	registeredLoaderHashCode Hash code cache for performance improvement
protected java.util.Map	unloadedClasses Cache for loaded classes

Constructor Summary

JDOClassLoaderResolver()
Constructor for non-PersistenceManager cases so there is no PM context loader.

JDOClassLoaderResolver(java.lang.ClassLoader pmLoader)
Constructor for PersistenceManager cases.

Method Summary

java.lang.Class	classForName(java.lang.String name) JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5).
java.lang.Class	classForName(java.lang.String name, boolean initialize) JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5)
java.lang.Class	classForName(java.lang.String name, java.lang.ClassLoader primary) JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5).
java.lang.Class	classForName(java.lang.String name, java.lang.ClassLoader primary, boolean initialize) JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5)
java.net.URL	getResource(java.lang.String resourceName) Finds the resource with the given name.
java.util.Enumeration	getResources(java.lang.String resourceName) Finds all the resources with the given name.
boolean	isAssignableFrom(java.lang.Class class_1, java.lang.String class_name_2) Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism.
boolean	isAssignableFrom(java.lang.String class_name_1, java.lang.Class class_2) Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism.
boolean	isAssignableFrom(java.lang.String class_name_1, java.lang.String class_name_2) Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism.
void	registerClassLoader(java.lang.ClassLoader loader) ClassLoader registered to load classes created at runtime

Methods inherited from class java.lang.Object

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

Field Detail

LOCALISER

protected static final Localiser LOCALISER

Localisation utility for output messages

pmContextLoader

protected final java.lang.ClassLoader pmContextLoader

ClassLoader initialised by the PM creation.

pmContextLoaderHashCode

protected int pmContextLoaderHashCode

Hash code cache for performance improvement

registeredLoader

protected java.lang.ClassLoader registeredLoader

ClassLoader registered to load runtime created classes.

registeredLoaderHashCode

protected int registeredLoaderHashCode

Hash code cache for performance improvement

loadedClasses

protected java.util.Map loadedClasses

Cache for loaded classes

unloadedClasses

protected java.util.Map unloadedClasses

Cache for loaded classes

Constructor Detail

JDOClassLoaderResolver

public JDOClassLoaderResolver(java.lang.ClassLoader pmLoader)

Constructor for PersistenceManager cases.

Parameters:

pmLoader - Loader from PM initialisation time.

JDOClassLoaderResolver

public JDOClassLoaderResolver()

Constructor for non-PersistenceManager cases so there is no PM context loader.

Method Detail

classForName

public java.lang.Class classForName(java.lang.String name,
                                    java.lang.ClassLoader primary)

JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5). Try 3 loaders, starting with user-supplied loader, then try the current thread's loader, and finally try the PM context loader. This method does not initialize the class

Specified by:

classForName in interface ClassLoaderResolver

Parameters:

name - Name of the Class to be loaded

primary - primary ClassLoader to use (or null)

Returns:

The class given the name, using the required loader.

Throws:

ClassNotResolvedException - if the class can't be found in the classpath

classForName

public java.lang.Class classForName(java.lang.String name,
                                    java.lang.ClassLoader primary,
                                    boolean initialize)

JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5)

Specified by:

classForName in interface ClassLoaderResolver

Parameters:

name - Name of the Class to be loaded

primary - the primary ClassLoader to use (or null)

initialize - whether to initialize the class or not.

Returns:

The Class given the name, using the specified ClassLoader

Throws:

ClassNotResolvedException - if the class can't be found in the classpath

classForName

public java.lang.Class classForName(java.lang.String name)

JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5). This method does not initialize the class

Specified by:

classForName in interface ClassLoaderResolver

Parameters:

name - Name of the Class to be loaded

Returns:

The class given the name, using the required loader.

classForName

public java.lang.Class classForName(java.lang.String name,
                                    boolean initialize)

JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5)

Specified by:

classForName in interface ClassLoaderResolver

Parameters:

name - Name of the Class to be loaded

initialize - whether to initialize the class or not.

Returns:

The Class given the name, using the specified ClassLoader

Throws:

ClassNotResolvedException - if the class can't be found in the classpath

isAssignableFrom

public boolean isAssignableFrom(java.lang.String class_name_1,
                                java.lang.String class_name_2)

Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);

Specified by:

isAssignableFrom in interface ClassLoaderResolver

Parameters:

class_name_1 - Name of first class

class_name_2 - Name of second class

Returns:

Whether Class 2 is assignable from Class 1

isAssignableFrom

public boolean isAssignableFrom(java.lang.String class_name_1,
                                java.lang.Class class_2)

Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);

Specified by:

isAssignableFrom in interface ClassLoaderResolver

Parameters:

class_name_1 - Name of first class

class_2 - Second class

Returns:

Whether Class 2 is assignable from Class 1

isAssignableFrom

public boolean isAssignableFrom(java.lang.Class class_1,
                                java.lang.String class_name_2)

Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);

Specified by:

isAssignableFrom in interface ClassLoaderResolver

Parameters:

class_1 - First class

class_name_2 - Name of second class

Returns:

Whether Class 2 is assignable from Class 1

registerClassLoader

public void registerClassLoader(java.lang.ClassLoader loader)

ClassLoader registered to load classes created at runtime

Specified by:

registerClassLoader in interface ClassLoaderResolver

Parameters:

loader - The ClassLoader in which classes are defined

getResources

public java.util.Enumeration getResources(java.lang.String resourceName)
                                   throws java.io.IOException

Finds all the resources with the given name.

Specified by:

getResources in interface ClassLoaderResolver

Parameters:

resourceName - the resource name. If resourceName starts with "/", remove it before searching.

Returns:

An enumeration of URL objects for the resource. If no resources could be found, the enumeration will be empty. Resources that the class loader doesn't have access to will not be in the enumeration.

Throws:

java.io.IOException - If I/O errors occur

See Also:

ClassLoader.getResources(java.lang.String)

getResource

public java.net.URL getResource(java.lang.String resourceName)

Finds the resource with the given name.

Specified by:

getResource in interface ClassLoaderResolver

Parameters:

resourceName - the path to resource name relative to the classloader root path. If resourceName starts with "/", remove it before searching.

Returns:

A URL object for reading the resource, or null if the resource could not be found or the invoker doesn't have adequate privileges to get the resource.

Throws:

java.io.IOException - If I/O errors occur

See Also:

ClassLoader.getResource(java.lang.String)