Package org.apache.activemq.transport.mqtt.strategy

Interface MQTTSubscriptionStrategy

All Known Implementing Classes:

AbstractMQTTSubscriptionStrategy, MQTTDefaultSubscriptionStrategy, MQTTVirtualTopicSubscriptionStrategy

public interface MQTTSubscriptionStrategy

Subscription management strategy used to control how MQTT clients subscribe to destination and how messages are addressed in order to arrive on the appropriate destinations.

Method Summary

Modifier and Type	Method	Description
MQTTProtocolConverter	getProtocolConverter()
MQTTSubscription	getSubscription(org.apache.activemq.command.ConsumerId consumer)	Lookup an MQTTSubscription instance based on known ConsumerId value.
void	initialize(MQTTProtocolConverter protocol)	Initialize the strategy before first use.
boolean	isControlTopic(org.apache.activemq.command.ActiveMQDestination destination)	Allows the protocol handler to interrogate an destination name to determine if it is equivalent to the MQTT control topic (starts with $).
void	onConnect(org.fusesource.mqtt.codec.CONNECT connect)	Allows the strategy to perform any needed actions on client connect prior to the CONNACK frame being sent back such as recovering old subscriptions and performing any clean session actions.
void	onReSubscribe(MQTTSubscription subscription)	Called when a client sends a duplicate subscribe request which should force any retained messages on that topic to be replayed again as though the client had just subscribed for the first time.
org.apache.activemq.command.ActiveMQDestination	onSend(String topicName)	Intercepts PUBLISH operations from the client and allows the strategy to map the target destination so that the send operation will land in the destinations that this strategy has mapped the incoming subscribe requests to.
String	onSend(org.apache.activemq.command.ActiveMQDestination destination)	Intercepts send operations from the broker and allows the strategy to map the target topic name so that the client sees a valid Topic name.
byte	onSubscribe(String topicName, org.fusesource.mqtt.client.QoS requestedQoS)	Called when a new Subscription is being requested.
byte	onSubscribe(org.fusesource.mqtt.client.Topic topic)	Called for each Topic that a client requests to subscribe to.
void	onUnSubscribe(String topicName)	Called when a client requests an un-subscribe a previous subscription.
void	setProtocolConverter(MQTTProtocolConverter parent)	Sets the MQTTProtocolConverter that is the parent of this strategy object.

Method Detail

initialize

void initialize(MQTTProtocolConverter protocol)
         throws MQTTProtocolException

Initialize the strategy before first use.

Parameters:

protocol - the MQTTProtocolConverter that is initializing the strategy

Throws:

MQTTProtocolException - if an error occurs during initialization.

onConnect

void onConnect(org.fusesource.mqtt.codec.CONNECT connect)
        throws MQTTProtocolException

Allows the strategy to perform any needed actions on client connect prior to the CONNACK frame being sent back such as recovering old subscriptions and performing any clean session actions.

Throws:

MQTTProtocolException - if an error occurs while processing the connect actions.

onSubscribe

byte onSubscribe(org.fusesource.mqtt.client.Topic topic)
          throws MQTTProtocolException

Called for each Topic that a client requests to subscribe to. The strategy needs check each Topic for duplicate subscription requests and change of QoS state.

Parameters:

topic - the MQTT Topic instance being subscribed to.

Returns:

the assigned QoS value given to the new subscription.

Throws:

MQTTProtocolException - if an error occurs while processing the subscribe actions.

onSubscribe

byte onSubscribe(String topicName,
                 org.fusesource.mqtt.client.QoS requestedQoS)
          throws MQTTProtocolException

Called when a new Subscription is being requested. This method allows the strategy to create a specific type of subscription for the client such as mapping topic subscriptions to Queues etc.

Parameters:

topicName - the requested Topic name to subscribe to.

requestedQoS - the QoS level that the client has requested for this subscription.

Returns:

the assigned QoS value given to the new subscription

Throws:

MQTTProtocolException - if an error occurs while processing the subscribe actions.

onReSubscribe

void onReSubscribe(MQTTSubscription subscription)
            throws MQTTProtocolException

Called when a client sends a duplicate subscribe request which should force any retained messages on that topic to be replayed again as though the client had just subscribed for the first time. The method should not unsubscribe the client as it might miss messages sent while the subscription is being recreated.

Parameters:

subscription - the MQTTSubscription that contains the subscription state.

Throws:

MQTTProtocolException

onUnSubscribe

void onUnSubscribe(String topicName)
            throws MQTTProtocolException

Called when a client requests an un-subscribe a previous subscription.

Parameters:

topicName - the name of the Topic the client wishes to unsubscribe from.

Throws:

MQTTProtocolException - if an error occurs during the un-subscribe processing.

onSend

org.apache.activemq.command.ActiveMQDestination onSend(String topicName)

Intercepts PUBLISH operations from the client and allows the strategy to map the target destination so that the send operation will land in the destinations that this strategy has mapped the incoming subscribe requests to.

Parameters:

topicName - the targeted Topic that the client sent the message to.

Returns:

an ActiveMQ Topic instance that lands the send in the correct destinations.

onSend

String onSend(org.apache.activemq.command.ActiveMQDestination destination)

Intercepts send operations from the broker and allows the strategy to map the target topic name so that the client sees a valid Topic name.

Parameters:

destination - the destination that the message was dispatched from

Returns:

an Topic name that is valid for the receiving client.

isControlTopic

boolean isControlTopic(org.apache.activemq.command.ActiveMQDestination destination)

Allows the protocol handler to interrogate an destination name to determine if it is equivalent to the MQTT control topic (starts with $). Since the mapped destinations that the strategy might alter the naming scheme the strategy must provide a way to reverse map and determine if the destination was originally an MQTT control topic.

Parameters:

destination - the destination to query.

Returns:

true if the destination is an MQTT control topic.

setProtocolConverter

void setProtocolConverter(MQTTProtocolConverter parent)

Sets the MQTTProtocolConverter that is the parent of this strategy object.

Parameters:

parent - the MQTTProtocolConverter that owns this strategy.

getProtocolConverter

MQTTProtocolConverter getProtocolConverter()

Returns:

the MQTTProtocolConverter that owns this strategy.

getSubscription

MQTTSubscription getSubscription(org.apache.activemq.command.ConsumerId consumer)

Lookup an MQTTSubscription instance based on known ConsumerId value.

Parameters:

consumer - the consumer ID to lookup.

Returns:

the MQTTSubscription for the consumer or null if no subscription exists.