URIUtil.java

/*
 * Copyright Aduna (http://www.aduna-software.com/) (c) 2007.
 *
 * Licensed under the Aduna BSD-style license.
 */
package org.openrdf.model.util;

import org.openrdf.model.URI;

/**
 * @author Arjohn Kampman
 */
public class URIUtil {

	/**
	 * Finds the index of the first local name character in an (non-relative)
	 * URI. This index is determined by the following the following steps:
	 * <ul>
	 * <li>Find the <em>first</em> occurrence of the '#' character,
	 * <li>If this fails, find the <em>last</em> occurrence of the '/'
	 * character,
	 * <li>If this fails, find the <em>last</em> occurrence of the ':'
	 * character.
	 * <li>Add <tt>1<tt> to the found index and return this value.
	 * </ul>
	 * Note that the third step should never fail as every legal (non-relative)
	 * URI contains at least one ':' character to seperate the scheme from the
	 * rest of the URI. If this fails anyway, the method will throw an
	 * {@link IllegalArgumentException}.
	 * 
	 * @param uri
	 *        A URI string.
	 * @return The index of the first local name character in the URI string. Note that
	 * this index does not reference an actual character if the algorithm determines
	 * that there is not local name. In that case, the return index is equal to the
	 * length of the URI string.
	 * @throws IllegalArgumentException
	 *         If the supplied URI string doesn't contain any of the separator
	 *         characters. Every legal (non-relative) URI contains at least one
	 *         ':' character to seperate the scheme from the rest of the URI.
	 */
	public static int getLocalNameIndex(String uri) {
		int separatorIdx = uri.indexOf('#');

		if (separatorIdx < 0) {
			separatorIdx = uri.lastIndexOf('/');
		}

		if (separatorIdx < 0) {
			separatorIdx = uri.lastIndexOf(':');
		}

		if (separatorIdx < 0) {
			throw new IllegalArgumentException("No separator character founds in URI: " + uri);
		}

		return separatorIdx + 1;
	}

	/**
	 * Checks whether the URI consisting of the specified namespace and local
	 * name has been split correctly according to the URI splitting rules
	 * specified in {@link URI}.
	 * 
	 * @param namespace
	 *        The URI's namespace, must not be <tt>null</tt>.
	 * @param localName
	 *        The URI's local name, must not be <tt>null</tt>.
	 * @return <tt>true</tt> if the specified URI has been correctly split into
	 *         a namespace and local name, <tt>false</tt> otherwise.
	 * @see URI
	 * @see #getLocalNameIndex(String)
	 */
	public static boolean isCorrectURISplit(String namespace, String localName) {
		assert namespace != null : "namespace must not be null";
		assert localName != null : "localName must not be null";

		if (namespace.length() == 0) {
			return false;
		}

		int nsLength = namespace.length();
		char lastNsChar = namespace.charAt(nsLength - 1);

		if (lastNsChar == '#' && namespace.lastIndexOf('#', nsLength - 2) == -1) {
			// namespace ends with a '#' and does not contain any futher '#'
			// characters
			return true;
		}
		else if (localName.indexOf('#') == -1 && localName.indexOf('/') == -1) {
			if (lastNsChar == '/') {
				// URI does not contain any '#' characters and the namespace ends
				// with the last '/' character
				return true;
			}
			else if (lastNsChar == ':' && localName.indexOf(':') == -1) {
				// URI does not contain any '#' or '/' characters and the namespace
				// ends with the last ':' character
				return true;
			}
		}

		return false;
	}
}