net.jini.core.lookup

Interface ServiceRegistrar

public interface ServiceRegistrar

Defines the interface to the lookup service. The interface is not a remote interface; each implementation of the lookup service exports proxy objects that implement the ServiceRegistrar interface local to the client, using an implementation-specific protocol to communicate with the actual remote server. All of the proxy methods obey normal RMI remote interface semantics except where explicitly noted. Two proxy objects are equal if they are proxies for the same lookup service. Every method invocation (on both ServiceRegistrar and ServiceRegistration) is atomic with respect to other invocations.

Since:

1.0

Author:

Sun Microsystems, Inc.

See Also:

ServiceRegistration

Field Summary

Fields

Modifier and Type	Field and Description
static int	TRANSITION_MATCH_MATCH An event is sent when the changed item matches the template both before and after the operation.
static int	TRANSITION_MATCH_NOMATCH An event is sent when the changed item matches the template before the operation, but doesn't match the template after the operation (this includes deletion of the item).
static int	TRANSITION_NOMATCH_MATCH An event is sent when the changed item doesn't match the template before the operation (this includes not existing), but does match the template after the operation.

Method Summary

Modifier and Type	Method and Description
Class[]	getEntryClasses(ServiceTemplate tmpl) Looks at all service items that match the specified template, finds every entry (among those service items) that either doesn't match any entry templates or is a subclass of at least one matching entry template, and returns the set of the (most specific) classes of those entries.
Object[]	getFieldValues(ServiceTemplate tmpl, int setIndex, String field) Looks at all service items that match the specified template, finds every entry (among those service items) that matches tmpl.attributeSetTemplates[setIndex], and returns the set of values of the specified field of those entries.
String[]	getGroups() Returns the set of groups that this lookup service is currently a member of.
LookupLocator	getLocator() Returns a LookupLocator that can be used if necessary for unicast discovery of the lookup service.
ServiceID	getServiceID() Returns the service ID of the lookup service.
Class[]	getServiceTypes(ServiceTemplate tmpl, String prefix) Looks at all service items that match the specified template, and for every service item finds the most specific type (class or interface) or types the service item is an instance of that are neither equal to, nor a superclass of, any of the service types in the template and that have names that start with the specified prefix, and returns the set of all such types.
Object	lookup(ServiceTemplate tmpl) Returns the service object (i.e., just ServiceItem.service) from an item matching the template, or null if there is no match.
ServiceMatches	lookup(ServiceTemplate tmpl, int maxMatches) Returns at most maxMatches items matching the template, plus the total number of items that match the template.
EventRegistration	notify(ServiceTemplate tmpl, int transitions, RemoteEventListener listener, MarshalledObject handback, long leaseDuration) Registers for event notification.
ServiceRegistration	register(ServiceItem item, long leaseDuration) Register a new service or re-register an existing service.

Field Detail

TRANSITION_MATCH_NOMATCH

static final int TRANSITION_MATCH_NOMATCH

An event is sent when the changed item matches the template before the operation, but doesn't match the template after the operation (this includes deletion of the item).

See Also:

Constant Field Values

TRANSITION_NOMATCH_MATCH

static final int TRANSITION_NOMATCH_MATCH

An event is sent when the changed item doesn't match the template before the operation (this includes not existing), but does match the template after the operation.

See Also:

Constant Field Values

TRANSITION_MATCH_MATCH

static final int TRANSITION_MATCH_MATCH

An event is sent when the changed item matches the template both before and after the operation.

See Also:

Constant Field Values

Method Detail

register

ServiceRegistration register(ServiceItem item,
                             long leaseDuration)
                      throws RemoteException

Register a new service or re-register an existing service. The method is defined so that it can be used in an idempotent fashion. Specifically, if a call to register results in a RemoteException (in which case the item might or might not have been registered), the caller can simply repeat the call to register with the same parameters, until it succeeds.

To register a new service, item.serviceID should be null. In that case, if item.service does not equal (using MarshalledObject.equals) any existing item's service object, then a new service ID will be assigned and included in the returned ServiceRegistration. The service ID is unique over time and space with respect to all other service IDs generated by all lookup services. If item.service does equal an existing item's service object, the existing item is first deleted from the lookup service (even if it has different attributes) and its lease is cancelled, but that item's service ID is reused for the newly registered item.

To re-register an existing service, or to register the service in any other lookup service, item.serviceID should be set to the same service ID that was returned by the initial registration. If an item is already registered under the same service ID, the existing item is first deleted (even if it has different attributes or a different service instance) and its lease is cancelled. Note that service object equality is not checked in this case, to allow for reasonable evolution of the service (e.g., the serialized form of the stub changes, or the service implements a new interface).

Any duplicate attribute sets included in a service item are eliminated in the stored representation of the item. The lease duration request is not exact; the returned lease is allowed to have a shorter (but not longer) duration than what was requested. The registration is persistent across restarts (crashes) of the lookup service until the lease expires or is cancelled.

Parameters:

item - service item to register

leaseDuration - requested lease duration, in milliseconds

Returns:

a ServiceRegistration in this lookup service for the specified service item

Throws:

RemoteException

lookup

Object lookup(ServiceTemplate tmpl)
       throws RemoteException

Returns the service object (i.e., just ServiceItem.service) from an item matching the template, or null if there is no match. If multiple items match the template, it is arbitrary as to which service object is returned. If the returned object cannot be deserialized, an UnmarshalException is thrown with the standard RMI semantics.

Parameters:

tmpl - template to match

Returns:

an object that represents a service that matches the specified template

Throws:

RemoteException

lookup

ServiceMatches lookup(ServiceTemplate tmpl,
                      int maxMatches)
               throws RemoteException

Returns at most maxMatches items matching the template, plus the total number of items that match the template. The return value is never null, and the returned items array is only null if maxMatches is zero. For each returned item, if the service object cannot be deserialized, the service field of the item is set to null and no exception is thrown. Similarly, if an attribute set cannot be deserialized, that element of the attributeSets array is set to null and no exception is thrown.

Parameters:

tmpl - template to match

maxMatches - maximum number of matches to return

Returns:

a ServiceMatches instance that contains at most maxMatches items matching the template, plus the total number of items that match the template. The return value is never null, and the returned items array is only null if maxMatches is zero.

Throws:

RemoteException

notify

EventRegistration notify(ServiceTemplate tmpl,
                         int transitions,
                         RemoteEventListener listener,
                         MarshalledObject handback,
                         long leaseDuration)
                  throws RemoteException

Registers for event notification. The registration is leased; the lease expiration request is not exact. The registration is persistent across restarts (crashes) of the lookup service until the lease expires or is cancelled. The event ID in the returned EventRegistration is unique at least with respect to all other active event registrations in this lookup service with different service templates or transitions.

While the event registration is in effect, a ServiceEvent is sent to the specified listener whenever a register, lease cancellation or expiration, or attribute change operation results in an item changing state in a way that satisfies the template and transition combination.

Parameters:

tmpl - template to match

transitions - bitwise OR of any non-empty set of transition values

listener - listener to send events to

handback - object to include in every ServiceEvent generated

leaseDuration - requested lease duration

Returns:

an EventRegistration object to the entity that registered the specified remote listener

Throws:

RemoteException

getEntryClasses

Class[] getEntryClasses(ServiceTemplate tmpl)
                 throws RemoteException

Looks at all service items that match the specified template, finds every entry (among those service items) that either doesn't match any entry templates or is a subclass of at least one matching entry template, and returns the set of the (most specific) classes of those entries. Duplicate classes are eliminated, and the order of classes within the returned array is arbitrary. Null (not an empty array) is returned if there are no such entries or no matching items. If a returned class cannot be deserialized, that element of the returned array is set to null and no exception is thrown.

Parameters:

tmpl - template to match

Returns:

an array of entry Classes (attribute sets) for every service that matches the specified template

Throws:

RemoteException

getFieldValues

Object[] getFieldValues(ServiceTemplate tmpl,
                        int setIndex,
                        String field)
                 throws NoSuchFieldException,
                        RemoteException

Looks at all service items that match the specified template, finds every entry (among those service items) that matches tmpl.attributeSetTemplates[setIndex], and returns the set of values of the specified field of those entries. Duplicate values are eliminated, and the order of values within the returned array is arbitrary. Null (not an empty array) is returned if there are no matching items. If a returned value cannot be deserialized, that element of the returned array is set to null and no exception is thrown.

Parameters:

tmpl - template to match

setIndex - index into tmpl.attributeSetTemplates

field - name of field of tmpl.attributeSetTemplates[setIndex]

Returns:

an array of objects that represents field values of entries associated with services that meet the specified matching criteria

Throws:

NoSuchFieldException - field does not name a field of the entry template

RemoteException

getServiceTypes

Class[] getServiceTypes(ServiceTemplate tmpl,
                        String prefix)
                 throws RemoteException

Looks at all service items that match the specified template, and for every service item finds the most specific type (class or interface) or types the service item is an instance of that are neither equal to, nor a superclass of, any of the service types in the template and that have names that start with the specified prefix, and returns the set of all such types. Duplicate types are eliminated, and the order of types within the returned array is arbitrary. Null (not an empty array) is returned if there are no such types. If a returned type cannot be deserialized, that element of the returned array is set to null and no exception is thrown.

Parameters:

tmpl - template to match

prefix - class name prefix

Returns:

an array of Classes of all services that either match the specified template or match the specified prefix

Throws:

RemoteException

getServiceID

ServiceID getServiceID()

Returns the service ID of the lookup service. Note that this does not make a remote call. A lookup service is always registered with itself under this service ID, and if a lookup service is configured to register itself with other lookup services, it will register with all of them using this same service ID.

Returns:

the service ID of the lookup service.

getLocator

LookupLocator getLocator()
                  throws RemoteException

Returns a LookupLocator that can be used if necessary for unicast discovery of the lookup service.

Returns:

a LookupLocator that can be used for unicast discovery of the lookup service, if necessary.

Throws:

RemoteException

getGroups

String[] getGroups()
            throws RemoteException

Returns the set of groups that this lookup service is currently a member of.

Returns:

a String array of groups that this lookup service is currently a member of.

Throws:

RemoteException