Java tutorial
/* * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.rmi; import java.rmi.registry.*; import java.net.MalformedURLException; import java.net.URI; import java.net.URISyntaxException; /** * The <code>Naming</code> class provides methods for storing and obtaining * references to remote objects in a remote object registry. Each method of * the <code>Naming</code> class takes as one of its arguments a name that * is a <code>java.lang.String</code> in URL format (without the * scheme component) of the form: * * <PRE> * //host:port/name * </PRE> * * <P>where <code>host</code> is the host (remote or local) where the registry * is located, <code>port</code> is the port number on which the registry * accepts calls, and where <code>name</code> is a simple string uninterpreted * by the registry. Both <code>host</code> and <code>port</code> are optional. * If <code>host</code> is omitted, the host defaults to the local host. If * <code>port</code> is omitted, then the port defaults to 1099, the * "well-known" port that RMI's registry, <code>rmiregistry</code>, uses. * * <P><em>Binding</em> a name for a remote object is associating or * registering a name for a remote object that can be used at a later time to * look up that remote object. A remote object can be associated with a name * using the <code>Naming</code> class's <code>bind</code> or * <code>rebind</code> methods. * * <P>Once a remote object is registered (bound) with the RMI registry on the * local host, callers on a remote (or local) host can lookup the remote * object by name, obtain its reference, and then invoke remote methods on the * object. A registry may be shared by all servers running on a host or an * individual server process may create and use its own registry if desired * (see <code>java.rmi.registry.LocateRegistry.createRegistry</code> method * for details). * * @author Ann Wollrath * @author Roger Riggs * @since 1.1 * @see java.rmi.registry.Registry * @see java.rmi.registry.LocateRegistry * @see java.rmi.registry.LocateRegistry#createRegistry(int) */ public final class Naming { /** * Disallow anyone from creating one of these */ private Naming() { } /** * Returns a reference, a stub, for the remote object associated * with the specified <code>name</code>. * * @param name a name in URL format (without the scheme component) * @return a reference for a remote object * @exception NotBoundException if name is not currently bound * @exception RemoteException if registry could not be contacted * @exception AccessException if this operation is not permitted * @exception MalformedURLException if the name is not an appropriately * formatted URL * @since 1.1 */ public static Remote lookup(String name) throws NotBoundException, java.net.MalformedURLException, RemoteException { ParsedNamingURL parsed = parseURL(name); Registry registry = getRegistry(parsed); if (parsed.name == null) return registry; return registry.lookup(parsed.name); } /** * Binds the specified <code>name</code> to a remote object. * * @param name a name in URL format (without the scheme component) * @param obj a reference for the remote object (usually a stub) * @exception AlreadyBoundException if name is already bound * @exception MalformedURLException if the name is not an appropriately * formatted URL * @exception RemoteException if registry could not be contacted * @exception AccessException if this operation is not permitted (if * originating from a non-local host, for example) * @since 1.1 */ public static void bind(String name, Remote obj) throws AlreadyBoundException, java.net.MalformedURLException, RemoteException { ParsedNamingURL parsed = parseURL(name); Registry registry = getRegistry(parsed); if (obj == null) throw new NullPointerException("cannot bind to null"); registry.bind(parsed.name, obj); } /** * Destroys the binding for the specified name that is associated * with a remote object. * * @param name a name in URL format (without the scheme component) * @exception NotBoundException if name is not currently bound * @exception MalformedURLException if the name is not an appropriately * formatted URL * @exception RemoteException if registry could not be contacted * @exception AccessException if this operation is not permitted (if * originating from a non-local host, for example) * @since 1.1 */ public static void unbind(String name) throws RemoteException, NotBoundException, java.net.MalformedURLException { ParsedNamingURL parsed = parseURL(name); Registry registry = getRegistry(parsed); registry.unbind(parsed.name); } /** * Rebinds the specified name to a new remote object. Any existing * binding for the name is replaced. * * @param name a name in URL format (without the scheme component) * @param obj new remote object to associate with the name * @exception MalformedURLException if the name is not an appropriately * formatted URL * @exception RemoteException if registry could not be contacted * @exception AccessException if this operation is not permitted (if * originating from a non-local host, for example) * @since 1.1 */ public static void rebind(String name, Remote obj) throws RemoteException, java.net.MalformedURLException { ParsedNamingURL parsed = parseURL(name); Registry registry = getRegistry(parsed); if (obj == null) throw new NullPointerException("cannot bind to null"); registry.rebind(parsed.name, obj); } /** * Returns an array of the names bound in the registry. The names are * URL-formatted (without the scheme component) strings. The array contains * a snapshot of the names present in the registry at the time of the * call. * * @param name a registry name in URL format (without the scheme * component) * @return an array of names (in the appropriate format) bound * in the registry * @exception MalformedURLException if the name is not an appropriately * formatted URL * @exception RemoteException if registry could not be contacted. * @since 1.1 */ public static String[] list(String name) throws RemoteException, java.net.MalformedURLException { ParsedNamingURL parsed = parseURL(name); Registry registry = getRegistry(parsed); String prefix = ""; if (parsed.port > 0 || !parsed.host.isEmpty()) prefix += "//" + parsed.host; if (parsed.port > 0) prefix += ":" + parsed.port; prefix += "/"; String[] names = registry.list(); for (int i = 0; i < names.length; i++) { names[i] = prefix + names[i]; } return names; } /** * Returns a registry reference obtained from information in the URL. */ private static Registry getRegistry(ParsedNamingURL parsed) throws RemoteException { return LocateRegistry.getRegistry(parsed.host, parsed.port); } /** * Dissect Naming URL strings to obtain referenced host, port and * object name. * * @return an object which contains each of the above * components. * * @exception MalformedURLException if given url string is malformed */ private static ParsedNamingURL parseURL(String str) throws MalformedURLException { try { return intParseURL(str); } catch (URISyntaxException ex) { /* With RFC 3986 URI handling, 'rmi://:<port>' and * '//:<port>' forms will result in a URI syntax exception * Convert the authority to a localhost:<port> form */ MalformedURLException mue = new MalformedURLException("invalid URL String: " + str); mue.initCause(ex); int indexSchemeEnd = str.indexOf(':'); int indexAuthorityBegin = str.indexOf("//:"); if (indexAuthorityBegin < 0) { throw mue; } if ((indexAuthorityBegin == 0) || ((indexSchemeEnd > 0) && (indexAuthorityBegin == indexSchemeEnd + 1))) { int indexHostBegin = indexAuthorityBegin + 2; String newStr = str.substring(0, indexHostBegin) + "localhost" + str.substring(indexHostBegin); try { return intParseURL(newStr); } catch (URISyntaxException inte) { throw mue; } catch (MalformedURLException inte) { throw inte; } } throw mue; } } private static ParsedNamingURL intParseURL(String str) throws MalformedURLException, URISyntaxException { URI uri = new URI(str); if (uri.isOpaque()) { throw new MalformedURLException("not a hierarchical URL: " + str); } if (uri.getFragment() != null) { throw new MalformedURLException("invalid character, '#', in URL name: " + str); } else if (uri.getQuery() != null) { throw new MalformedURLException("invalid character, '?', in URL name: " + str); } else if (uri.getUserInfo() != null) { throw new MalformedURLException("invalid character, '@', in URL host: " + str); } String scheme = uri.getScheme(); if (scheme != null && !scheme.equals("rmi")) { throw new MalformedURLException("invalid URL scheme: " + str); } String name = uri.getPath(); if (name != null) { if (name.startsWith("/")) { name = name.substring(1); } if (name.length() == 0) { name = null; } } String host = uri.getHost(); if (host == null) { host = ""; try { /* * With 2396 URI handling, forms such as 'rmi://host:bar' * or 'rmi://:<port>' are parsed into a registry based * authority. We only want to allow server based naming * authorities. */ uri.parseServerAuthority(); } catch (URISyntaxException use) { // Check if the authority is of form ':<port>' String authority = uri.getAuthority(); if (authority != null && authority.startsWith(":")) { // Convert the authority to 'localhost:<port>' form authority = "localhost" + authority; try { uri = new URI(null, authority, null, null, null); // Make sure it now parses to a valid server based // naming authority uri.parseServerAuthority(); } catch (URISyntaxException use2) { throw new MalformedURLException("invalid authority: " + str); } } else { throw new MalformedURLException("invalid authority: " + str); } } } int port = uri.getPort(); if (port == -1) { port = Registry.REGISTRY_PORT; } return new ParsedNamingURL(host, port, name); } /** * Simple class to enable multiple URL return values. */ private static class ParsedNamingURL { String host; int port; String name; ParsedNamingURL(String host, int port, String name) { this.host = host; this.port = port; this.name = name; } } }