Package org.apache.commons.discovery.tools

Class ResourceUtils

java.lang.Object

org.apache.commons.discovery.tools.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.

Author:

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

Constructor Summary

Constructors

Constructor	Description
ResourceUtils()

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

ResourceUtils

public ResourceUtils()

Method Detail

getPackageName

public static java.lang.String getPackageName(java.lang.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(java.lang.Class spi,
                                   java.lang.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.

Throws:

DiscoveryException

loadProperties

public static java.util.Properties loadProperties(java.lang.Class spi,
                                                  java.lang.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.