org.apache.commons.discovery.tools
Class ResourceUtils

java.lang.Object
  org.apache.commons.discovery.tools.ResourceUtils

public class ResourceUtils
extends 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.

Constructor Summary

ResourceUtils()

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 qualified 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 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.

Parameters:

clazz - The class from which the package has to be extracted

Returns:

The string representation of the input class package

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:

spi - The SPI type

resourceName - The name of the resource to load.

loaders - the class loaders holder

Returns:

The discovered Resource instance

Throws:

DiscoveryException - if the class implementing the SPI cannot be found, cannot be loaded and instantiated, or if the resulting class does not implement (or extend) the SPI

loadProperties

public static Properties loadProperties(Class<?> spi,
                                        String propertiesFileName,
                                        ClassLoaders classLoaders)
                                 throws DiscoveryException

Load named property file, optionally qualified 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:

spi - The SPI type

propertiesFileName - The property file name.

classLoaders - The class loaders holder

Returns:

The loaded named property file, in Properties format

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.