PropertyLoader.java

package gov.nist.registry.common2.test.io;




import java.io.InputStream;

import java.util.Enumeration;

import java.util.Locale;

import java.util.Properties;

import java.util.ResourceBundle;



//----------------------------------------------------------------------------

/**

 * A simple class for loading java.util.Properties backed by .properties files

 * deployed as classpath resources. See individual methods for details.

 * 

 * @author (C) <a href="http://www.javaworld.com/columns/jw-qna-index.shtml">Vlad Roubtsov</a>, 2003

 */

public

abstract class PropertyLoader

{

	// public: ................................................................



	/**

	 * Looks up a resource named 'name' in the classpath. The resource must map

	 * to a file with .properties extention. The name is assumed to be absolute

	 * and can use either "/" or "." for package segment separation with an

	 * optional leading "/" and optional ".properties" suffix. Thus, the

	 * following names refer to the same resource:

	 * <pre>

	 * some.pkg.Resource

	 * some.pkg.Resource.properties

	 * some/pkg/Resource

	 * some/pkg/Resource.properties

	 * /some/pkg/Resource

	 * /some/pkg/Resource.properties

	 * </pre>

	 * 

	 * @param name classpath resource name [may not be null]

	 * @param loader classloader through which to load the resource [null

	 * is equivalent to the application loader]

	 * 

	 * @return resource converted to java.util.Properties [may be null if the

	 * resource was not found and THROW_ON_LOAD_FAILURE is false]

	 * @throws IllegalArgumentException if the resource was not found and

	 * THROW_ON_LOAD_FAILURE is true

	 */

	public static Properties loadProperties (String name, ClassLoader loader)

	{

		if (name == null)

			throw new IllegalArgumentException ("null input: name");



		if (name.startsWith ("/"))

			name = name.substring (1);



		if (name.endsWith (SUFFIX))

			name = name.substring (0, name.length () - SUFFIX.length ());



		Properties result = null;



		InputStream in = null;

		try

		{

			if (loader == null) loader = ClassLoader.getSystemClassLoader ();



			if (LOAD_AS_RESOURCE_BUNDLE)

			{    

				name = name.replace ('/', '.');



				// throws MissingResourceException on lookup failures:

					final ResourceBundle rb = ResourceBundle.getBundle (name,

							Locale.getDefault (), loader);



					result = new Properties ();

					for (Enumeration keys = rb.getKeys (); keys.hasMoreElements ();)

					{

						final String key = (String) keys.nextElement ();

						final String value = rb.getString (key);



						result.put (key, value);

					} 

			}

			else

			{

				name = name.replace ('.', '/');



				if (! name.endsWith (SUFFIX))

					name = name.concat (SUFFIX);



				// returns null on lookup failures:

					in = loader.getResourceAsStream (name);

					if (in != null)

					{

						result = new Properties ();

						result.load (in); // can throw IOException

					}

			}

		}

		catch (Exception e)

		{

			result = null;

		}

		finally

		{

			if (in != null) try { in.close (); } catch (Throwable ignore) {}

		}



		if (THROW_ON_LOAD_FAILURE && (result == null))

		{

			throw new IllegalArgumentException ("could not load [" + name + "]" +

					" as " + (LOAD_AS_RESOURCE_BUNDLE

							? "a resource bundle"

									: "a classloader resource"));

		}



		return result;

	}



	/**

	 * A convenience overload of {@link #loadProperties(String, ClassLoader)}

	 * that uses the current thread's context classloader. A better strategy

	 * would be to use techniques shown in

	 * http://www.javaworld.com/javaworld/javaqa/2003-06/01-qa-0606-load.html 

	 */

	public static Properties loadProperties (final String name)

	{

		return loadProperties (name,

				Thread.currentThread ().getContextClassLoader ());

	}



	// protected: .............................................................



	// package: ...............................................................



	// private: ...............................................................





	private PropertyLoader () {} // this class is not extentible





	private static final boolean THROW_ON_LOAD_FAILURE = true;

	private static final boolean LOAD_AS_RESOURCE_BUNDLE = false;

	private static final String SUFFIX = ".properties";



} // end of class

//----------------------------------------------------------------------------