ClassUtil.java

/*******************************************************************************
 * Copyright (c) 2010 Markus Alexander Kuppe.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Markus Alexander Kuppe (ecf-dev_eclipse.org <at> lemmster <dot> de) - initial API and implementation
 ******************************************************************************/
package org.eclipse.ecf.core.util.reflection;

import java.lang.reflect.Method;
import java.util.*;

/**
 * @since 3.3
 */
public class ClassUtil {

	private static Map convertor = new HashMap();

	static {
		convertor.put(boolean.class, Boolean.class);
		convertor.put(byte.class, Byte.class);
		convertor.put(char.class, Character.class);
		convertor.put(double.class, Double.class);
		convertor.put(float.class, Float.class);
		convertor.put(int.class, Integer.class);
		convertor.put(long.class, Long.class);
		convertor.put(short.class, Short.class);
	}

	/**
	 * @param aClass The Class providing method under question (Must not be null)
	 * @param aMethodName The method name to search for (Must not be null)
	 * @param someParameterTypes Method arguments (May be null or parameters)
	 * @return A match. If more than one method matched (due to overloading) an arbitrary match is taken
	 * @throws NoSuchMethodException If a match cannot be found
	 */
	public static Method getMethod(final Class aClass, String aMethodName, final Class[] someParameterTypes) throws NoSuchMethodException {
		// no args makes matching simple
		if (someParameterTypes == null || someParameterTypes.length == 0) {
			return aClass.getMethod(aMethodName, (Class[]) null);
		}
		return getMethod(aClass.getMethods(), aMethodName, someParameterTypes);
	}

	/**
	 * @param aClass The Class providing method under question (Must not be null)
	 * @param aMethodName The method name to search for (Must not be null)
	 * @param someParameterTypes Method arguments (May be null or parameters)
	 * @return A match. If more than one method matched (due to overloading) an arbitrary match is taken
	 * @throws NoSuchMethodException If a match cannot be found
	 */
	public static Method getDeclaredMethod(final Class aClass, String aMethodName, final Class[] someParameterTypes) throws NoSuchMethodException {
		// no args makes matching simple
		if (someParameterTypes == null || someParameterTypes.length == 0) {
			return aClass.getDeclaredMethod(aMethodName, (Class[]) null);
		}
		return getMethod(aClass.getDeclaredMethods(), aMethodName, someParameterTypes);
	}

	private static Method getMethod(final Method[] candidates, String aMethodName, final Class[] someParameterTypes) throws NoSuchMethodException {
		// match parameters to determine callee
		final int parameterCount = someParameterTypes.length;
		aMethodName = aMethodName.intern();

		final TreeSet matches = new TreeSet(new MethodComparator(someParameterTypes));
		OUTER: for (int i = 0; i < candidates.length; i++) {
			final Method candidate = candidates[i];
			final String candidateMethodName = candidate.getName().intern();
			final Class[] candidateParameterTypes = candidate.getParameterTypes();
			final int candidateParameterCount = candidateParameterTypes.length;
			if (candidateParameterCount == parameterCount && aMethodName == candidateMethodName) {
				for (int j = 0; j < candidateParameterCount; j++) {
					final Class clazzA = candidateParameterTypes[j];
					final Class clazzB = someParameterTypes[j];
					if (clazzB != null && !isAssignableFrom(clazzA, clazzB)) {
						continue OUTER;
					}
				}
				matches.add(candidate);
			}
		}

		// if no match has been found, fail with NSME
		if (matches.size() == 0) {
			throw new NoSuchMethodException("No such method: " + aMethodName + "(" + Arrays.asList(someParameterTypes) + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		}
		return (Method) matches.first();
	}

	// extends Class.isAssingable(Class) with autoboxing
	private static boolean isAssignableFrom(Class clazzA, Class clazzB) {
		if (!(clazzA.isPrimitive() ^ clazzB.isPrimitive())) {
			return clazzA.isAssignableFrom(clazzB);
		} else if (clazzA.isPrimitive()) {
			final Class oClazzA = (Class) convertor.get(clazzA);
			return oClazzA.isAssignableFrom(clazzB);
		} else {
			final Class oClazzB = (Class) convertor.get(clazzB);
			return clazzA.isAssignableFrom(oClazzB);
		}
	}

	private static class MethodComparator implements Comparator {

		private final Class[] parameterTypes;

		public MethodComparator(Class[] someParameterTypes) {
			parameterTypes = someParameterTypes;
		}

		public int compare(Object object1, Object object2) {
			final Class[] pt1 = ((Method) object1).getParameterTypes();
			final Class[] pt2 = ((Method) object2).getParameterTypes();

			if (Arrays.equals(pt1, pt2)) {
				return 0;
			} else if (Arrays.equals(parameterTypes, pt1)) {
				return -1;
			} else {
				return 1;
			}
		}
	}
}