descriptorclassloader.java

PIY(Program It Yourself)是一个基于Java的应用程序开发环境

package piy;

import java.io.File;
import java.lang.reflect.*;

/**
* Loads in Descriptor classes, and the classes they are describing.
* @author David Vivash
* @version 1.0.1, 28/11/00
*/
public final class DescriptorClassLoader
{
	/**
	* Retrieves all of the classes from the supplied directory that can be cast
	* to baseClass and secondBaseClass, If baseClass is Object, all of the classes in the directory 
	* will be returned. The classes should be accessible as "directoryName.className"
	* or "directoryName.subDirectoryName.className" etc. That is, the classes in the
	* directory specified must belong to a pckage with the directoryName being the
	* root package name. It will also load all of the "Descriptor" files in the directory
	* and map them to the classes loaded.  If a loaded class has no descriptor, a 
	* StandardDescriptor class will be created for it.
	* @param directory the (absolute) path to the directory containing the classes
	* @param prefix the (classname) prefix representing the full package name up to the 
	* final directory which equals the specified directory
	* @param baseClass the top level class from which all the returned classes can
	* be cast to
	* @param secondBaseClass another top level class to which the returned classes can be cast.  Set to Object
	* if only one class cast is needed and is represented in baseClass
	* @param recurse set to true if the classloader should load from subdirectories as well
	* @return an array containing all of the valid classes found
	* @throws FileNotFoundException if directory is not found or does not represent a directory
	*/
	public static Descriptor[] getDescriptors(File directory, String prefix, Class baseClass, Class secondBaseClass, boolean recurse) throws java.io.FileNotFoundException
	{

		Class[] descriptors	= PIYClassLoader.getClasses(directory, prefix, Descriptor.class, null, recurse);
		Class[] classes		= PIYClassLoader.getClasses(directory, prefix, baseClass, secondBaseClass, recurse);

		Descriptor[] toReturn = new Descriptor[classes.length]; 

		boolean found = false;
		int j=0;

		for (int i=0; i<classes.length; i++)
		{
			found = false;
			j=0;

			while(!found && j<descriptors.length) {
				try{
					Method getClass = descriptors[j].getMethod("getDescribedClass", new Class[0]);

					if (getClass.invoke(descriptors[j].newInstance(), new Class[0]) == classes[i]) {
						found = true;
						toReturn[i] = (Descriptor)descriptors[j].newInstance();
					}
				} catch (Exception e) {
					//ignore
				}

				j++;
			}

			if (!found)	//create standard descriptor for the class
				toReturn[i] = new StandardDescriptor(classes[i], classes[i].getName());
		}

		return toReturn;
	}

}