org.apache.commons.discovery.tools

Class ResourceUtils


public class ResourceUtils
extends java.lang.Object

Mechanisms to locate and load a class. The load methods locate a class only. The find methods locate a class and verify that the class implements an given interface or extends a given class.
Authors:
Richard A. Sitze
Craig R. McClanahan
Costin Manolache

Method Summary

static String
getPackageName(Class clazz)
Get package name.
static Resource
getResource(Class spi, String resourceName, ClassLoaders loaders)
Load the resource resourceName.
static Properties
loadProperties(Class spi, String propertiesFileName, ClassLoaders classLoaders)
Load named property file, optionally qualifed by spi's package name as per Class.getResource.

Method Details

getPackageName

public static String getPackageName(Class clazz)
Get package name. Not all class loaders 'keep' package information, in which case Class.getPackage() returns null. This means that calling Class.getPackage().getName() is unreliable at best.

getResource

public static Resource getResource(Class spi,
                                   String resourceName,
                                   ClassLoaders loaders)
            throws DiscoveryException
Load the resource resourceName. Try each classloader in succession, until first succeeds, or all fail. If all fail and resouceName is not absolute (doesn't start with '/' character), then retry with packageName/resourceName after changing all '.' to '/'.
Parameters:
resourceName - The name of the resource to load.

loadProperties

public static Properties loadProperties(Class spi,
                                        String propertiesFileName,
                                        ClassLoaders classLoaders)
            throws DiscoveryException
Load named property file, optionally qualifed by spi's package name as per Class.getResource. A property file is loaded using the following sequence of class loaders:
  • Thread Context Class Loader
  • DiscoverSingleton's Caller's Class Loader
  • SPI's Class Loader
  • DiscoverSingleton's (this class) Class Loader
  • System Class Loader
Parameters:
propertiesFileName - The property file name.
Returns:
Instance of a class implementing the SPI.
Throws:
DiscoveryException - Thrown if the name of a class implementing the SPI cannot be found, if the class cannot be loaded and instantiated, or if the resulting class does not implement (or extend) the SPI.

Copyright (c) 2002 - Apache Software Foundation