org.datanucleus

Interface ClassLoaderResolver

All Known Implementing Classes:

ClassLoaderResolverImpl

public interface ClassLoaderResolver

Class to allow resolution and loading of classes in a persistence framework. Implementations are to define the rules for resolving the classes. For example JDO (used outside a J2EE container) would likely differ from EJB3 (used within a J2EE container). The search class path order is:

• the primary classloader argument
• the primary classloader (set using setPrimary and kept in ThreadLocal variable).
• the current thread context classloader.
• the pm classloader.
• the registered classloader.
• the user registered classloader.

Method Summary

Methods

Modifier and Type	Method and Description
Class	classForName(String name) Class loading method.
Class	classForName(String name, boolean initialize) Class loading method, allowing for initialisation of the class.
Class	classForName(String name, ClassLoader primary) Class loading method, allowing specification of a primary loader.
Class	classForName(String name, ClassLoader primary, boolean initialize) Class loading method, allowing specification of a primary loader and whether the class should be initialised or not.
URL	getResource(String resourceName, ClassLoader primary) Finds the resource with the given name.
Enumeration<URL>	getResources(String resourceName, ClassLoader primary) Finds all the resources with the given name.
boolean	isAssignableFrom(Class class_1, String class_name_2) Method to test whether the type represented by the specified class_name_2 parameter can be converted to the type represented by class_1 parameter.
boolean	isAssignableFrom(String class_name_1, Class class_2) Method to test whether the type represented by the specified class_2 parameter can be converted to the type represented by class_name_1 parameter.
boolean	isAssignableFrom(String class_name_1, String class_name_2) Method to test whether the type represented by the specified class_name_2 parameter can be converted to the type represented by class_name_1 parameter.
void	registerUserClassLoader(ClassLoader loader) ClassLoader registered by users to load classes.
void	setPrimary(ClassLoader primary) Sets the primary classloader for the current thread.
void	setRuntimeClassLoader(ClassLoader loader) ClassLoader registered to load classes created at runtime.
void	unsetPrimary() Unsets the primary classloader for the current thread

Method Detail

classForName

Class classForName(String name,
                 ClassLoader primary)

Class loading method, allowing specification of a primary loader. This method does not initialize the class

Parameters:

name - Name of the Class to be loaded

primary - the primary ClassLoader to use (or null)

Returns:

The Class given the name, using the specified ClassLoader

Throws:

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

classForName

Class classForName(String name,
                 ClassLoader primary,
                 boolean initialize)

Class loading method, allowing specification of a primary loader and whether the class should be initialised or not.

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

Class classForName(String name)

Class loading method. This method does not initialize the class

Parameters:

name - Name of the Class to be loaded

Returns:

The Class given the name, using the specified ClassLoader

classForName

Class classForName(String name,
                 boolean initialize)

Class loading method, allowing for initialisation of the class.

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

isAssignableFrom

boolean isAssignableFrom(String class_name_1,
                       Class class_2)

Method to test whether the type represented by the specified class_2 parameter can be converted to the type represented by class_name_1 parameter.

Parameters:

class_name_1 - Class name

class_2 - Class to compare against

Returns:

Whether they are assignable

isAssignableFrom

boolean isAssignableFrom(Class class_1,
                       String class_name_2)

Method to test whether the type represented by the specified class_name_2 parameter can be converted to the type represented by class_1 parameter.

Parameters:

class_1 - First class

class_name_2 - Class name to compare against

Returns:

Whether they are assignable

isAssignableFrom

boolean isAssignableFrom(String class_name_1,
                       String class_name_2)

Method to test whether the type represented by the specified class_name_2 parameter can be converted to the type represented by class_name_1 parameter.

Parameters:

class_name_1 - Class name

class_name_2 - Class name to compare against

Returns:

Whether they are assignable

setRuntimeClassLoader

void setRuntimeClassLoader(ClassLoader loader)

ClassLoader registered to load classes created at runtime. One ClassLoader can be registered, and if one ClassLoader is already registered, the registered ClassLoader is replaced by loader.

Parameters:

loader - The ClassLoader in which classes are defined

registerUserClassLoader

void registerUserClassLoader(ClassLoader loader)

ClassLoader registered by users to load classes. One ClassLoader can be registered, and if one ClassLoader is already registered, the registered ClassLoader is replaced by loader.

Parameters:

loader - The ClassLoader in which classes are loaded

getResources

Enumeration<URL> getResources(String resourceName,
                            ClassLoader primary)
                              throws IOException

Finds all the resources with the given name.

Parameters:

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

primary - the primary ClassLoader to use (or null)

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:

IOException - If I/O errors occur

See Also:

ClassLoader.getResources(java.lang.String)

getResource

URL getResource(String resourceName,
              ClassLoader primary)

Finds the resource with the given name.

Parameters:

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

primary - the primary ClassLoader to use (or null)

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:

IOException - If I/O errors occur

See Also:

ClassLoader.getResource(java.lang.String)

setPrimary

void setPrimary(ClassLoader primary)

Sets the primary classloader for the current thread. The primary should be kept in a ThreadLocal variable.

Parameters:

primary - the primary classloader

unsetPrimary

void unsetPrimary()

Unsets the primary classloader for the current thread