com.atlassian.plugin.util

Class ClassLoaderUtils

java.lang.Object

com.atlassian.plugin.util.ClassLoaderUtils

public class ClassLoaderUtils
extends Object

This class is extremely useful for loading resources and classes in a fault tolerant manner that works across different applications servers.

It has come out of many months of frustrating use of multiple application servers at Atlassian, please don't change things unless you're sure they're not going to break in one server or another!

Version:

$Revision: 1.1 $

Author:

$Author: mcannon $

Constructor Summary

Constructors

Constructor and Description
ClassLoaderUtils()

Method Summary

Modifier and Type	Method and Description
static URL	getResource(String resourceName, Class<?> callingClass) Load a given resource.
static InputStream	getResourceAsStream(String resourceName, Class<?> callingClass) This is a convenience method to load a resource as a stream.
static Enumeration<URL>	getResources(String resourceName, Class<?> callingClass) returns all found resources as java.net.URLs.
static <T> Class<T>	loadClass(String className, Class<?> callingClass) Load a class with a given name.
static void	printClassLoader() Prints the current classloader hierarchy - useful for debugging.
static void	printClassLoader(ClassLoader cl) Prints the classloader hierarchy from a given classloader - useful for debugging.

Methods inherited from class java.lang.Object

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

Constructor Detail

ClassLoaderUtils

public ClassLoaderUtils()

Method Detail

loadClass

public static <T> Class<T> loadClass(String className,
                                     Class<?> callingClass)
                              throws ClassNotFoundException

Load a class with a given name.

It will try to load the class in the following order:

• From Thread.currentThread().getContextClassLoader() if non-null
• Using the basic Class.forName(java.lang.String)
• From ClassLoaderUtil.class.getClassLoader()
• From the callingClass.getClassLoader()

Parameters:

className - The name of the class to load

callingClass - The Class object of the calling object

Throws:

ClassNotFoundException - If the class cannot be found anywhere.

getResource

public static URL getResource(String resourceName,
                              Class<?> callingClass)

Load a given resource.

This method will try to load the resource using the following methods (in order):

• From Thread.currentThread().getContextClassLoader()
• From ClassLoaderUtil.class.getClassLoader()
• From the callingClass.getClassLoader()

Parameters:

resourceName - The name of the resource to load

callingClass - The Class object of the calling object

getResources

public static Enumeration<URL> getResources(String resourceName,
                                            Class<?> callingClass)
                                     throws IOException

returns all found resources as java.net.URLs.

This method will try to load the resource using the following methods (in order):

• From Thread.currentThread().getContextClassLoader()
• From ClassLoaderUtil.class.getClassLoader()
• From the callingClass.getClassLoader()

Parameters:

resourceName - The name of the resource to load

callingClass - The Class object of the calling object

Throws:

IOException

getResourceAsStream

public static InputStream getResourceAsStream(String resourceName,
                                              Class<?> callingClass)

This is a convenience method to load a resource as a stream. The algorithm used to find the resource is given in getResource()

Parameters:

resourceName - The name of the resource to load

callingClass - The Class object of the calling object

printClassLoader

public static void printClassLoader()

Prints the current classloader hierarchy - useful for debugging.

printClassLoader

public static void printClassLoader(ClassLoader cl)

Prints the classloader hierarchy from a given classloader - useful for debugging.