org.sapia.ubik.rmi.naming
Class ServiceLocator

java.lang.Object
  org.sapia.ubik.rmi.naming.ServiceLocator

public class ServiceLocator
extends java.lang.Object

This class implements the Service Locator pattern. It acts as a universal lookup "helper", in conjunction with pluggable ServiceHandler instances. The ServiceLocator encapsulates one to many service handlers; for a given lookup, the locator retrieves the appropriate locator and then delegates the lookup to the latter, returning the result to the caller.

Service handlers are plugged into the locator in one of the following ways:

• By specifying service handlers as part of the system properties. This requires mapping a service handler uri scheme to the handler's class. The property name in this case must respect the following syntax: ubik.rmi.naming.service.handler.uri_scheme (where 'uri_scheme' is the scheme that is used to retreive a given object.
• by calling this class' registerHandler(...) method.

For example, given the following service handler: com.acme.MyServiceHandler, the configuration could be created has follows:

 System.setProperty("ubik.rmi.naming.service.handler.acme", "com.acme.MyServiceHandler");
 

Then, latter on, a lookup can be performed using this class:

 Object remote = ServiceLocator.lookup("acme://localhost:7070");
 

As shown above, the "acme" uri that was used to register the handler is then used in the lookup. Using the scheme of the passed in URI, the lookup(...) method delegates the operation to the proper handler.

IMPORTANT: If service handlers are configured through system properties, it is important to do so before invoking the ServiceLocator class in any way: the latter retrieves the configured handlers in a static initializer, which would prevent the handlers from being discovered if configured after the ServiceLocator class' initialization.

Author:

Yanick Duchesne

Copyright:

Copyright © 2002-2003 Sapia Open Source Software. All Rights Reserved.

License:

Read the license.txt file of the jar or visit the license page at the Sapia OSS web site

Field Summary

static java.lang.String	HANDLER_PATTERN Corresponds to the prefix of properties specifying service handlers.
static java.lang.String	UBIK_SCHEME The URI scheme for the default service handler: ubik.
static int	UNDEFINED_PORT This constant identifies an unidentified port.

Constructor Summary

ServiceLocator()

Method Summary

static java.lang.Object	lookup(java.lang.String url) Performs the lookup for the given path.
static void	registerHandler(java.lang.String scheme, ServiceHandler handler) Registers the given handler with the passed in scheme.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

UNDEFINED_PORT

public static final int UNDEFINED_PORT

This constant identifies an unidentified port.

See Also:

Constant Field Values

HANDLER_PATTERN

public static final java.lang.String HANDLER_PATTERN

Corresponds to the prefix of properties specifying service handlers. The prefix is: 'ubik.rmi.naming.service.handler'.

See Also:

Constant Field Values

UBIK_SCHEME

public static final java.lang.String UBIK_SCHEME

The URI scheme for the default service handler: ubik.

See Also:

JNDIHandler, Constant Field Values

Constructor Detail

ServiceLocator

public ServiceLocator()

Method Detail

lookup

public static java.lang.Object lookup(java.lang.String url)
                               throws javax.naming.NameNotFoundException,
                                      javax.naming.NamingException

Performs the lookup for the given path.

Parameters:

url - the url of the object to look up.

Returns:

an Object

Throws:

javax.naming.NameNotFoundException - if no object could be found for the given url.

javax.naming.NamingException - if an error occurs while performing the lookup.

registerHandler

public static void registerHandler(java.lang.String scheme,
                                   ServiceHandler handler)
                            throws java.lang.IllegalStateException

Registers the given handler with the passed in scheme.

Parameters:

scheme - a URI scheme.

handler - a ServiceHandler.

Throws:

java.lang.IllegalStateException - if a handler is already registered with the given scheme.