naming.java

来自「Actual Java RMI implementation」· Java 代码 · 共 286 行

/*
 * @(#)Naming.java	1.18 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
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 the remote object registry. The
 * <code>Naming</code> class's methods take, as one of their arguments, a name
 * that is a URL formatted <code>java.lang.String</code> 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).
 *
 * @version 1.13, 09/05/99
 * @author  Ann Wollrath
 * @author  Roger Riggs
 * @since   JDK1.1
 * @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 URL-formatted name for the remote object
     * @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 JDK1.1
     */
    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 URL-formatted name for the remote object
     * @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 JDK1.1
     */
    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 URL-formatted name associated with a remote object
     * @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 JDK1.1
     */
    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 URL-formatted name associated with the remote object
     * @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 JDK1.1
     */
    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 strings. The array contains a snapshot of the names
     * present in the registry at the time of the call.
     *
     * @param name a URL-formatted name that specifies the remote registry
     * @return an array of names (in the appropriate URL 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 JDK1.1
     */
    public static String[] list(String name)
	throws RemoteException, java.net.MalformedURLException
    {
	ParsedNamingURL parsed = parseURL(name);
	Registry registry = getRegistry(parsed);

	String prefix = "rmi:";
 	if (parsed.port > 0 || !parsed.host.equals(""))
	    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 {
	    URI uri = new URI(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 = "";
		if (uri.getPort() == -1) {
		    /* handle URIs with explicit port but no host
		     * (e.g., "//:1098/foo"); although they do not strictly
		     * conform to RFC 2396, Naming's javadoc explicitly allows
		     * them.
		     */
		    String authority = uri.getAuthority();
		    if (authority != null && authority.startsWith(":")) {
			authority = "localhost" + authority;
			uri = new URI(null, authority, null, null, null);
		    }
		}
	    }
	    int port = uri.getPort();
	    if (port == -1) {
		port = Registry.REGISTRY_PORT;
	    }
	    return new ParsedNamingURL(host, port, name);

	} catch (URISyntaxException ex) {
	    throw (MalformedURLException) new MalformedURLException(
		"invalid URL string: " + str).initCause(ex);
	}
    }

    /**
     * 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;
	}
    }
}