org.apache.commons.discovery.resource
Class ClassLoaders

java.lang.Object
  |
  +--org.apache.commons.discovery.resource.ClassLoaders

public class ClassLoaders

extends java.lang.Object

There are many different contexts in which loaders can be used. This provides a holder for a set of class loaders, so that they don't have to be build back up everytime...

Author:

Richard A. Sitze, Craig R. McClanahan, Costin Manolache

Field Summary

protected java.util.Vector

classLoaders

Constructor Summary

ClassLoaders()
Construct a new class loader set

Method Summary

java.lang.ClassLoader	get(int idx)
static ClassLoaders	getAppLoaders(java.lang.Class spi, java.lang.Class factory, boolean prune) Utility method.
static ClassLoaders	getLibLoaders(java.lang.Class spi, java.lang.Class factory, boolean prune) Utility method.
boolean	isAncestor(java.lang.ClassLoader classLoader) Check to see if classLoader is an ancestor of any contained class loader.
void	put(java.lang.ClassLoader classLoader) Specify a new class loader to be used in searching.
void	put(java.lang.ClassLoader classLoader, boolean prune) Specify a new class loader to be used in searching.
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

classLoaders

protected java.util.Vector classLoaders

Constructor Detail

ClassLoaders

public ClassLoaders()

Construct a new class loader set

Method Detail

size

public int size()

get

public java.lang.ClassLoader get(int idx)

put

public void put(java.lang.ClassLoader classLoader)

Specify a new class loader to be used in searching. The order of loaders determines the order of the result. It is recommended to add the most specific loaders first.

put

public void put(java.lang.ClassLoader classLoader,
                boolean prune)

Specify a new class loader to be used in searching. The order of loaders determines the order of the result. It is recommended to add the most specific loaders first.

Parameters:

prune - if true, verify that the class loader is not an Ancestor (@see isAncestor) before adding it to our list.

isAncestor

public boolean isAncestor(java.lang.ClassLoader classLoader)

Check to see if classLoader is an ancestor of any contained class loader. This can be used to eliminate redundant class loaders IF all class loaders defer to parent class loaders before resolving a class. It may be that this is not always true. Therefore, this check is not done internally to eliminate redundant class loaders, but left to the discretion of the user.

getLibLoaders

public static ClassLoaders getLibLoaders(java.lang.Class spi,
                                         java.lang.Class factory,
                                         boolean prune)

Utility method. Returns a preloaded ClassLoaders instance containing the following class loaders, in order:

• spi.getClassLoader
• seeker.getClassLoader
• System Class Loader

Note that the thread context class loader is NOT present. This is a reasonable set of loaders to try if the resource to be found should be restricted to a libraries containing the SPI and Factory.

Parameters:

spi - WHAT is being looked for (an implementation of this class, a default property file related to this class).

factory - WHO is performing the lookup.

prune - Determines if ancestors are allowed to be loaded or not.

getAppLoaders

public static ClassLoaders getAppLoaders(java.lang.Class spi,
                                         java.lang.Class factory,
                                         boolean prune)

Utility method. Returns a preloaded ClassLoaders instance containing the following class loaders, in order:

• Thread Context Class Loader
• spi.getClassLoader
• seeker.getClassLoader
• System Class Loader

Note that the thread context class loader IS present. This is a reasonable set of loaders to try if the resource to be found may be provided by an application.

Parameters:

spi - WHAT is being looked for (an implementation of this class, a default property file related to this class).

factory - WHO is performing the lookup (factory).

prune - Determines if ancestors are allowed to be loaded or not.