Poco::OSP

class ServiceRegistry

Library: OSP
Package: Service
Header: Poco/OSP/ServiceRegistry.h

Description

The ServiceRegistry allows a bundle to provide services to other bundle, and to find services provided by other bundles.

A bundle can provide and register arbitrary services in the form of interface classes. Every service a bundle provides must be implemented in a class derived from Service. Service objects are reference counted.

A service can be implemented and registered as a singleton, meaning there exists exacty one instance of the service providing services to all bundles in the system. Alternatively, a service can be implemented and registered using a service factory. A service factory provides a unique instance of the service class to everyone requesting the Service object.

If a service is to be registered using a service factory, a corresponding subclass of ServiceFactory must be implemented for the Service class. An instance of the ServiceFactory must then be registered instead of the Service object itself.

Member Summary

Member Functions: createListener, find, findByName, registerService, unregisterService

Constructors

ServiceRegistry

ServiceRegistry();

Creates the ServiceRegistry.

Destructor

~ServiceRegistry

~ServiceRegistry();

Destroys the ServiceRegistry.

Member Functions

createListener inline

template < typename Delegate > ServiceListener::Ptr createListener(
    const std::string & query,
    const Delegate & registeredDelegate,
    const Delegate & unregisteredDelegate
);

Returns a new ServiceListener instance that will listen for services matching the given query.

See find() for a description of the query language syntax.

The given registeredDelegate will be called when a new service has been registered that matches the given query. It will be added to the ServiceListener's serviceRegistered event.

The given unregisteredDelegate will be called when a previously matched service has been unregistered. It will be added to the ServiceListener's serviceUnregistered event.

If services that match the given query already have been registered, the registeredDelegate will be immediately called for each matching service.

Both delegates must accept a const Poco::OSP::ServiceRef::Ptr& as argument.

find inline

std::size_t find(
    const std::string & query,
    std::vector < ServiceRef::Ptr > & results
) const;

Looks up a service(s) with the properties specified by the given query.

The string given in query must be a valid query expression according to the syntax given below.

Fills the given results vector with ServiceRef objects matching the given query and returns the number of matches found.

The query language syntax is as follows:

expr          ::= andExpr ["||" andExpr]
andExpr       ::= relExpr ["&&" relExpr]
relExpr       ::= ["!"] (id [relOp value | "=~" matchExpr]) | subExpr
subExpr       ::= "(" expr ")"
relOp         ::= "==" | "!=" | "<" | "<=" | ">" | ">="
value         ::= numLiteral | boolLiteral | stringLiteral
numLiteral    ::= [sign] digit*"."digit*["E"["+" | "-"]digit*]
boolLiteral   ::= "true" | "false"
stringLiteral ::= '"' char* '"'
matchExpr     ::= stringLiteral | regExpr
regExpr       ::= delim char+ delim /* valid Perl regular expression,
                                       enclosed in delim */
delim         ::= "/" | "#"

Examples for valid queries:

  • name == "com.appinf.osp.sample.service" - a simple string comparison for equality.
  • majorVersion > 1 && minorVersion >= 5 - numeric comparisons and logical AND.
  • name =~ "com.appinf.osp.*" && someProperty - simple pattern matching and test for existence of someProperty.
  • someProperty =~ /[0-9]+/ - regular expression matching.

find

std::size_t find(
    const QLExpr & expr,
    std::vector < ServiceRef::Ptr > & results
) const;

An overload of find() that takes a parsed query in the form of a QLExpr object instead of a query string.

find

std::vector < ServiceRef::Ptr > find(
    const std::string & query
) const;

A convenience overload of find() that directly returns a vector of ServiceRef objects.

findByName

ServiceRef::ConstPtr findByName(
    const std::string & name
) const;

Looks up a service with the given name.

Returns a ServiceRef for the given service, or a NULL pointer if the service does not exist.

registerService

ServiceRef::Ptr registerService(
    const std::string & name,
    Service::Ptr pService,
    const Properties & props
);

Registers the service object given in pService under the given name, and with the given service properties.

Returns a ServiceRef object for the registered service that can later be used to update the service properties.

Throws a Poco::ExistsException if a service with that name has already been registered.

unregisterService

void unregisterService(
    const std::string & name
);

Unregisters the service with the given name.

Throws a Poco::NotFoundException if no service with the given name exists.

unregisterService

void unregisterService(
    ServiceRef::Ptr pServiceRef
);

Unregisters the service specified by pServiceRef.

Variables

PROP_NAME static

static const std::string PROP_NAME;

PROP_TYPE static

static const std::string PROP_TYPE;

serviceRegistered

Poco::BasicEvent < ServiceEvent > serviceRegistered;

Fired whenever a new service has been registered.

serviceUnregistered

Poco::BasicEvent < ServiceEvent > serviceUnregistered;

Fired whenever a service has been unregistered.