BundleContext

class cppmicroservices::BundleContext

A bundle’s execution context within the framework.

The context is used to grant access to other methods so that this bundle can interact with the framework.

BundleContext methods allow a bundle to:

  • Install other bundles.
  • Subscribe to events published by the framework.
  • Register service objects with the framework service registry.
  • Retrieve ServiceReferences from the framework service registry.
  • Get and release service objects for a referenced service.
  • Get the list of bundles installed in the framework.
  • Get the Bundle object for a bundle.

A BundleContext object will be created and provided to the bundle associated with this context when it is started using the BundleActivator::Start method. The same BundleContext object will be passed to the bundle associated with this context when it is stopped using the BundleActivator::Stop method. A BundleContext object is generally for the private use of its associated bundle and is not meant to be shared with other bundles in the bundle environment.

The Bundle object associated with a BundleContext object is called the context bundle.

The BundleContext object is only valid during the execution of its context bundle; that is, during the period when the context bundle is started. If the BundleContext object is used subsequently, a std::logic_error is thrown. The BundleContext object is never reused after its context bundle is stopped.

The framework is the only entity that can create BundleContext objects.

Remark
This class is thread safe.

Public Functions

BundleContext()

Constructs an invalid BundleContext object.

Valid bundle context objects can only be created by the framework and are supplied to a bundle via its BundleActivator or as a return value of the GetBundleContext() method.

See
operator bool() const

bool operator==(const BundleContext &rhs) const

Compares this BundleContext object with the specified bundle context.

Valid BundleContext objects are equal if and only if they represent the same context. Invalid BundleContext objects are always considered to be equal.

Return
true if this BundleContext object is equal to rhs, false otherwise.
Parameters

bool operator!=(const BundleContext &rhs) const

Compares this BundleContext object with the specified bundle context for inequality.

Return
Returns the result of !(*this == rhs).
Parameters

bool operator<(const BundleContext &rhs) const

Compares this BundleContext with the specified bundle context for order.

How valid BundleContext objects are ordered is an implementation detail and must not be relied on. Invalid BundleContext objects will always compare greater then valid BundleContext objects.

Return
true if this object is orderded before rhs, false otherwise.
Parameters

operator bool() const

Tests this BundleContext object for validity.

Invalid BundleContext objects are created by the default constructor or can be returned by certain framework methods if the context bundle has been uninstalled.

A BundleContext object can become invalid by assigning a nullptr to it or if the context bundle is stopped.

Return
true if this BundleContext object is valid and can safely be used, false otherwise.

BundleContext &operator=(std::nullptr_t)

Releases any resources held or locked by this BundleContext and renders it invalid.

Any GetProperty(const std::string &key) const

Returns the value of the specified property.

If the key is not found in the Framework properties, the method returns an empty Any.

Return
The value of the requested property, or an empty Any if the property is undefined.
Parameters
  • key: The name of the requested property.

AnyMap GetProperties() const

Returns all known properties.

Return
A map of all framework properties.

Bundle GetBundle() const

Returns the Bundle object associated with this BundleContext.

This bundle is called the context bundle.

Return
The Bundle object associated with this BundleContext.
Exceptions

Bundle GetBundle(long id) const

Returns the bundle with the specified identifier.

Return
A Bundle object or nullptr if the identifier does not match any previously installed bundle.
Parameters
  • id: The identifier of the bundle to retrieve.
Exceptions
  • std::logic_error: If the framework instance is not active.
  • std::runtime_error: If this BundleContext is no longer valid.

std::vector<Bundle> GetBundles(const std::string &location) const

Get the bundles with the specified bundle location.

Return
The requested {Bundle}s or an empty list.
Parameters
  • location: The location of the bundles to get.
Exceptions
  • std::logic_error: If the framework instance is not active.
  • std::runtime_error: If the BundleContext is no longer valid.

std::vector<Bundle> GetBundles() const

Returns a list of all known bundles.

This method returns a list of all bundles installed in the bundle environment at the time of the call to this method. This list will also contain bundles which might already have been stopped.

Return
A std::vector of Bundle objects which will hold one object per known bundle.
Exceptions

ServiceRegistrationU RegisterService(const InterfaceMapConstPtr &service, const ServiceProperties &properties = ServiceProperties ())

Registers the specified service object with the specified properties under the specified class names into the framework.

A ServiceRegistration object is returned. The ServiceRegistration object is for the private use of the bundle registering the service and should not be shared with other bundles. The registering bundle is defined to be the context bundle. Other bundles can locate the service by using either the GetServiceReferences or GetServiceReference method.

A bundle can register a service object that implements the ServiceFactory or PrototypeServiceFactory interface to have more flexibility in providing service objects to other bundles.

The following steps are taken when registering a service:

  1. The framework adds the following service properties to the service properties from the specified ServiceProperties (which may be omitted): A property named Constants::SERVICE_ID identifying the registration number of the service A property named Constants::OBJECTCLASS containing all the specified classes. A property named Constants::SERVICE_SCOPE identifying the scope of the service. Properties with these names in the specified ServiceProperties will be ignored.
  2. The service is added to the framework service registry and may now be used by other bundles.
  3. A service event of type ServiceEvent::SERVICE_REGISTERED is fired.
  4. A ServiceRegistration object for this registration is returned.

Note
This is a low-level method and should normally not be used directly. Use one of the templated RegisterService methods instead.
Return
A ServiceRegistration object for use by the bundle registering the service to update the service’s properties or to unregister the service.
See

ServiceRegistration

ServiceFactory

PrototypeServiceFactory

Parameters
  • service: A shared_ptr to a map of interface identifiers to service objects.
  • properties: The properties for this service. The keys in the properties object must all be std::string objects. See Constants for a list of standard service property keys. Changes should not be made to this object after calling this method. To update the service’s properties the ServiceRegistration::SetProperties method must be called. The set of properties may be omitted if the service has no properties.
Exceptions
  • std::runtime_error: If this BundleContext is no longer valid, or if there are case variants of the same key in the supplied properties map.
  • std::invalid_argument: If the InterfaceMap is empty, or if a service is registered as a null class.

template <class I1, class... Interfaces, class Impl>
ServiceRegistration<I1, Interfaces...> RegisterService(const std::shared_ptr<Impl> &impl, const ServiceProperties &properties = ServiceProperties ())

Registers the specified service object with the specified properties using the specified interfaces types with the framework.

This method is provided as a convenience when registering a service under two interface classes whose type is available to the caller. It is otherwise identical to RegisterService(const InterfaceMap&, const ServiceProperties&) but should be preferred since it avoids errors in the string literal identifying the class name or interface identifier.

Example usage: 

class MyService2 : public InterfaceA, public InterfaceB
{};

std::shared_ptr<MyService2> myService = std::make_shared<MyService2>();
context.RegisterService<InterfaceA, InterfaceB>(myService);
Return
A ServiceRegistration object for use by the bundle registering the service to update the service’s properties or to unregister the service.
See
RegisterService(const InterfaceMap&, const ServiceProperties&)
Template Parameters
  • I1: The first interface type under which the service can be located.
  • Interfaces: Additional interface types under which the service can be located.
Parameters
  • impl: A shared_ptr to the service object
  • properties: The properties for this service.
Exceptions
  • std::logic_error: If this BundleContext is no longer valid.
  • ServiceException: If the service type S is invalid or the service object is nullptr.

template <class I1, class... Interfaces>
ServiceRegistration<I1, Interfaces...> RegisterService(const std::shared_ptr<ServiceFactory> &factory, const ServiceProperties &properties = ServiceProperties ())

Registers the specified service factory as a service with the specified properties using the specified template argument as service interface type with the framework.

This method is provided as a convenience when factory will only be registered under a single class name whose type is available to the caller. It is otherwise identical to RegisterService(const InterfaceMap&, const ServiceProperties&) but should be preferred since it avoids errors in the string literal identifying the class name or interface identifier.

Example usage: 

class MyService2 : public InterfaceA, public InterfaceB
{};

class MyServiceFactory : public ServiceFactory
{
  virtual InterfaceMapConstPtr GetService(const Bundle& /*bundle*/, const ServiceRegistrationBase& /*registration*/)
  {
    return MakeInterfaceMap<InterfaceA,InterfaceB>(std::make_shared<MyService2>());
  }

  virtual void UngetService(const Bundle& /*bundle*/, const ServiceRegistrationBase& /*registration*/,
                            const InterfaceMapConstPtr& /*service*/)
  {

  }
};

std::shared_ptr<MyServiceFactory> myServiceFactory = std::make_shared<MyServiceFactory>();
context.RegisterService<InterfaceA,InterfaceB>(ToFactory(myServiceFactory));
Return
A ServiceRegistration object for use by the bundle registering the service to update the service’s properties or to unregister the service.
See
RegisterService(const InterfaceMap&, const ServiceProperties&)
Template Parameters
  • I1: The first interface type under which the service can be located.
  • Interfaces: Additional interface types under which the service can be located.
Parameters
  • factory: A shared_ptr to the ServiceFactory object.
  • properties: The properties for this service.
Exceptions
  • std::logic_error: If this BundleContext is no longer valid.
  • ServiceException: If the service type S is invalid or the service factory object is nullptr.

std::vector<ServiceReferenceU> GetServiceReferences(const std::string &clazz, const std::string &filter = std::string())

Returns a list of ServiceReference objects.

The returned list contains services that were registered under the specified class and match the specified filter expression.

The list is valid at the time of the call to this method. However, since the framework is a very dynamic environment, services can be modified or unregistered at any time.

The specified filter expression is used to select the registered services whose service properties contain keys and values that satisfy the filter expression. See LDAPFilter for a description of the filter syntax. If the specified filter is empty, all registered services are considered to match the filter. If the specified filter expression cannot be parsed, an std::invalid_argument will be thrown with a human-readable message where the filter became unparsable.

The result is a list of ServiceReference objects for all services that meet all of the following conditions:

  • If the specified class name, clazz, is not empty, the service must have been registered with the specified class name. The complete list of class names with which a service was registered is available from the service’s objectClass property.
  • If the specified filter is not empty, the filter expression must match the service.

Return
A list of ServiceReference objects or an empty list if no services are registered that satisfy the search.
Parameters
  • clazz: The class name with which the service was registered or an empty string for all services.
  • filter: The filter expression or empty for all services.
Exceptions
  • std::invalid_argument: If the specified filter contains an invalid filter expression that cannot be parsed.
  • std::runtime_error: If this BundleContext is no longer valid.
  • std:: logic_error If the ServiceRegistrationBase object is invalid, or if the service is unregistered.

template <class S>
std::vector<ServiceReference<S>> GetServiceReferences(const std::string &filter = std::string())

Returns a list of ServiceReference objects.

The returned list contains services that were registered under the interface id of the template argument S and match the specified filter expression.

This method is identical to GetServiceReferences(const std::string&, const std::string&) except that the class name for the service object is automatically deduced from the template argument.

Return
A list of ServiceReference objects or an empty list if no services are registered which satisfy the search.
See
GetServiceReferences(const std::string&, const std::string&)
Template Parameters
  • S: The type under which the requested service objects must have been registered.
Parameters
  • filter: The filter expression or empty for all services.
Exceptions
  • std::invalid_argument: If the specified filter contains an invalid filter expression that cannot be parsed.
  • std::logic_error: If this BundleContext is no longer valid.
  • ServiceException: If the service type S is invalid.

ServiceReferenceU GetServiceReference(const std::string &clazz)

Returns a ServiceReference object for a service that implements and was registered under the specified class.

The returned ServiceReference object is valid at the time of the call to this method. However as the Micro Services framework is a very dynamic environment, services can be modified or unregistered at any time.

This method is the same as calling BundleContext::GetServiceReferences(const std::string&, const std::string&) with an empty filter expression. It is provided as a convenience for when the caller is interested in any service that implements the specified class.

If multiple such services exist, the service with the highest ranking (as specified in its Constants::SERVICE_RANKING property) is returned.

If there is a tie in ranking, the service with the lowest service ID (as specified in its Constants::SERVICE_ID property); that is, the service that was registered first is returned.

Return
A ServiceReference object, or an invalid ServiceReference if no services are registered which implement the named class.
See
GetServiceReferences(const std::string&, const std::string&)
Parameters
  • clazz: The class name with which the service was registered.
Exceptions

template <class S>
ServiceReference<S> GetServiceReference()

Returns a ServiceReference object for a service that implements and was registered under the specified template class argument.

This method is identical to GetServiceReference(const std::string&) except that the class name for the service object is automatically deduced from the template argument.

Return
A ServiceReference object, or an invalid ServiceReference if no services are registered which implement the type S.
See

GetServiceReference(const std::string&)

GetServiceReferences(const std::string&)

Template Parameters
  • S: The type under which the requested service must have been registered.
Exceptions

std::shared_ptr<void> GetService(const ServiceReferenceBase &reference)

Returns the service object referenced by the specified ServiceReferenceBase object.

A bundle’s use of a service is tracked by the bundle’s use count of that service. Each call to GetService(const ServiceReference<S>&) increments the context bundle’s use count by one. The deleter function of the returned shared_ptr object is responsible for decrementing the context bundle’s use count.

When a bundle’s use count for a service drops to zero, the bundle should no longer use that service.

This method will always return an empty object when the service associated with this reference has been unregistered.

The following steps are taken to get the service object:

  1. If the service has been unregistered, empty object is returned.
  2. The context bundle’s use count for this service is incremented by one.
  3. If the context bundle’s use count for the service is currently one and the service was registered with an object implementing the ServiceFactory interface, the ServiceFactory::GetService method is called to create a service object for the context bundle. This service object is cached by the framework. While the context bundle’s use count for the service is greater than zero, subsequent calls to get the services’s service object for the context bundle will return the cached service object. If the ServiceFactory object throws an exception, empty object is returned and a warning is logged.
  4. A shared_ptr to the service object is returned.

Return
A shared_ptr to the service object associated with reference. An empty shared_ptr is returned if the service is not registered or the ServiceFactory threw an exception
See
ServiceFactory
Parameters
  • reference: A reference to the service.
Exceptions

InterfaceMapConstPtr GetService(const ServiceReferenceU &reference)
template <class S>
std::shared_ptr<S> GetService(const ServiceReference<S> &reference)

Returns the service object referenced by the specified ServiceReference object.

This is a convenience method which is identical to void* GetService(const ServiceReferenceBase&) except that it casts the service object to the supplied template argument type

Return
A shared_ptr to the service object associated with reference. An empty object is returned if the service is not registered, the ServiceFactory threw an exception or the service could not be cast to the desired type.
See

GetService(const ServiceReferenceBase&)

ServiceFactory

Template Parameters
  • S: The type the service object will be cast to.
Exceptions
  • std::runtime_error: If this BundleContext is no longer valid.
  • std::invalid_argument: If the specified ServiceReference is invalid (default constructed).

template <class S>
ServiceObjects<S> GetServiceObjects(const ServiceReference<S> &reference)

Returns the ServiceObjects object for the service referenced by the specified ServiceReference object.

The ServiceObjects object can be used to obtain multiple service objects for services with prototype scope. For services with singleton or bundle scope, the ServiceObjects::GetService() method behaves the same as the GetService(const ServiceReference<S>&) method and the ServiceObjects::UngetService(const ServiceReferenceBase&) method behaves the same as the UngetService(const ServiceReferenceBase&) method. That is, only one, use-counted service object is available from the ServiceObjects object.

Return
A ServiceObjects object for the service associated with the specified reference or an invalid instance if the service is not registered.
See
PrototypeServiceFactory
Template Parameters
  • S: Type of Service.
Parameters
  • reference: A reference to the service.
Exceptions
  • std::runtime_error: If this BundleContext is no longer valid.
  • std::invalid_argument: If the specified ServiceReference is invalid (default constructed or the service has been unregistered)

void AddServiceListener(const ServiceListener &delegate, const std::string &filter = std::string())
void RemoveServiceListener(const ServiceListener &delegate)
void AddBundleListener(const BundleListener &delegate)
void RemoveBundleListener(const BundleListener &delegate)
void AddFrameworkListener(const FrameworkListener &listener)
void RemoveFrameworkListener(const FrameworkListener &listener)
template <class R>
void cppmicroservices::BundleContext::AddServiceListener(R * receiver, void(R::*)(const ServiceEvent &) callback, const std::string & filter = std::string())

Adds the specified callback with the specified filter to the context bundles’s list of listeners.

See LDAPFilter for a description of the filter syntax. Listeners are notified when a service has a lifecycle state change.

You must take care to remove registered listeners befor the receiver object is destroyed. However, the Micro Services framework takes care of removing all listeners registered by this context bundle’s classes after the bundle is stopped.

If the context bundle’s list of listeners already contains a pair (r,c) of receiver and callback such that (r == receiver && c == callback), then this method replaces that callback’s filter (which may be empty) with the specified one (which may be empty).

The callback is called if the filter criteria is met. To filter based upon the class of the service, the filter should reference the Constants::OBJECTCLASS property. If filter is empty, all services are considered to match the filter.

When using a filter, it is possible that the ServiceEvents for the complete lifecycle of a service will not be delivered to the callback. For example, if the filter only matches when the property x has the value 1, the callback will not be called if the service is registered with the property x not set to the value 1. Subsequently, when the service is modified setting property x to the value 1, the filter will match and the callback will be called with a ServiceEvent of type SERVICE_MODIFIED. Thus, the callback will not be called with a ServiceEvent of type SERVICE_REGISTERED.

See

ServiceEvent

RemoveServiceListener()

Template Parameters
  • R: The type of the receiver (containing the member function to be called)
Parameters
  • receiver: The object to connect to.
  • callback: The member function pointer to call.
  • filter: The filter criteria.
Exceptions
  • std::invalid_argument: If filter contains an invalid filter string that cannot be parsed.
  • std::runtime_error: If this BundleContext is no longer valid.

template <class R>
void cppmicroservices::BundleContext::RemoveServiceListener(R * receiver, void(R::*)(const ServiceEvent &) callback)

Removes the specified callback from the context bundle’s list of listeners.

If the (receiver,callback) pair is not contained in this context bundle’s list of listeners, this method does nothing.

See
AddServiceListener()
Template Parameters
  • R: The type of the receiver (containing the member function to be removed)
Parameters
  • receiver: The object from which to disconnect.
  • callback: The member function pointer to remove.
Exceptions

template <class R>
void cppmicroservices::BundleContext::AddBundleListener(R * receiver, void(R::*)(const BundleEvent &) callback)

Adds the specified callback to the context bundles’s list of listeners.

Listeners are notified when a bundle has a lifecycle state change.

If the context bundle’s list of listeners already contains a pair (r,c) of receiver and callback such that (r == receiver && c == callback), then this method does nothing.

See
BundleEvent
Template Parameters
  • R: The type of the receiver (containing the member function to be called)
Parameters
  • receiver: The object to connect to.
  • callback: The member function pointer to call.
Exceptions

template <class R>
void cppmicroservices::BundleContext::RemoveBundleListener(R * receiver, void(R::*)(const BundleEvent &) callback)

Removes the specified callback from the context bundle’s list of listeners.

If the (receiver,callback) pair is not contained in this context bundle’s list of listeners, this method does nothing.

See
AddBundleListener()
Template Parameters
  • R: The type of the receiver (containing the member function to be removed)
Parameters
  • receiver: The object from which to disconnect.
  • callback: The member function pointer to remove.
Exceptions

template <class R>
void cppmicroservices::BundleContext::AddFrameworkListener(R * receiver, void(R::*)(const FrameworkEvent &) callback)

Adds the specified callback to the context bundles’s list of framework listeners.

Listeners are notified of framework events.

If the context bundle’s list of listeners already contains a pair (r,c) of receiver and callback such that (r == receiver && c == callback), then this method does nothing.

See
FrameworkEvent
Template Parameters
  • R: The type of the receiver (containing the member function to be called)
Parameters
  • receiver: The object to connect to.
  • callback: The member function pointer to call.
Exceptions

template <class R>
void cppmicroservices::BundleContext::RemoveFrameworkListener(R * receiver, void(R::*)(const FrameworkEvent &) callback)

Removes the specified callback from the context bundle’s list of framework listeners.

If the (receiver,callback) pair is not contained in this context bundle’s list of listeners, this method does nothing.

See
AddFrameworkListener()
Template Parameters
  • R: The type of the receiver (containing the member function to be removed)
Parameters
  • receiver: The object from which to disconnect.
  • callback: The member function pointer to remove.
Exceptions

std::string GetDataFile(const std::string &filename) const

Get the absolute path for a file or directory in the persistent storage area provided for the bundle.

The absolute path for the base directory of the persistent storage area provided for the context bundle by the Framework can be obtained by calling this method with an empty string as filename.

Return
The absolute path to the persistent storage area for the given file name.
Parameters
  • filename: A relative name to the file or directory to be accessed.
Exceptions

std::vector<Bundle> InstallBundles(const std::string &location)

Installs all bundles from the bundle library at the specified location.

The following steps are required to install a bundle:

  1. If a bundle containing the same install location is already installed, the Bundle object for that bundle is returned.
  2. The bundle’s associated resources are allocated. The associated resources minimally consist of a unique identifier and a persistent storage area if the platform has file system support. If this step fails, a std::runtime_error is thrown.
  3. A bundle event of type BundleEvent::BUNDLE_INSTALLED is fired.
  4. The Bundle object for the newly or previously installed bundle is returned.

Remark
An install location is an absolute path to a shared library or executable file which may contain several bundles, i. e. acts as a bundle library.
Return
The Bundle objects of the installed bundle library.
Parameters
  • location: The location of the bundle library to install.
Exceptions
  • std::runtime_error: If the BundleContext is no longer valid, or if the installation failed.
  • std::logic_error: If the framework instance is no longer active