com.sap.cds.services.utils.messaging.service

Class AbstractMessagingService

java.lang.Object

com.sap.cds.services.ServiceDelegator

com.sap.cds.services.utils.messaging.service.AbstractMessagingService

All Implemented Interfaces:

MessagingService, Service

public abstract class AbstractMessagingService
extends ServiceDelegator
implements MessagingService

Implementation of the MessagingService interface.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	forceListening
protected static String	FORMAT_CLOUDEVENTS
protected MessageQueue	queue
protected CdsRuntime	runtime
protected CdsProperties.Messaging.MessagingServiceConfig	serviceConfig

Fields inherited from interface com.sap.cds.services.messaging.MessagingService

COMPOSITE_NAME, EVENT_MESSAGING_ERROR

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractMessagingService(CdsProperties.Messaging.MessagingServiceConfig serviceConfig, CdsRuntime runtime)

Method Summary

Modifier and Type	Method and Description
protected void	cloudEventsFormatter(TopicMessageEventContext context)
protected boolean	createOrUpdateQueuesAndSubscriptions() Performs the initialization of the messaging service, by initializing the queues and registering the topic subscriptions.
protected abstract void	createQueue(String name, Map<String,String> properties) Request the broker for creating a queue with the specified queue name.
protected abstract void	createQueueSubscription(String queue, String topic) Requests the broker for creating a queue topic subscription.
protected void	defaultErrorHandler(MessagingErrorEventContext context)
void	emit(EventContext context)
void	emit(String topic, Map<String,Object> message)
void	emit(String topic, String message)
protected abstract void	emitTopicMessage(String topic, TopicMessageEventContext topicMessageEventContext) Performs the message emit on the messaging broker.
protected BiPredicate<MessageTopic,String>	getTopicMatcher() The topic matcher is used when the broker subscribes to a topic pattern.
void	init() Performs the initialization of the messaging service, by initializing the queues and registering the topic subscriptions.
protected boolean	isCloudEventsFormat()
void	on(String[] events, String[] entities, int order, Handler handler)
protected abstract void	registerQueueListener(String queue, MessagingBrokerQueueListener listener) Registers the MessagingBrokerQueueListener implementation to the specified queue of the message broker.
protected abstract void	removeQueue(String name) Request the broker for queue deletion with all its subscriptions.
protected void	sendMessageEvent(TopicMessageEventContext context)
void	stop() Used to stop the resources allocated by the messaging service, e.g.
protected String	toFullyQualifiedQueueName(MessageQueue queue) Translates the queue name corresponding the broker queue name specification.
protected String	toFullyQualifiedTopicName(String event, boolean inbound) Translates the given event definition to the broker environment specific name.

Methods inherited from class com.sap.cds.services.ServiceDelegator

after, after, before, before, getDelegatedService, getName, on

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.sap.cds.services.Service

after, after, after, after, after, before, before, before, before, before, create, getName, on, on, on, on

Field Detail

FORMAT_CLOUDEVENTS

protected static final String FORMAT_CLOUDEVENTS

See Also:

Constant Field Values

serviceConfig

protected final CdsProperties.Messaging.MessagingServiceConfig serviceConfig

runtime

protected final CdsRuntime runtime

queue

protected final MessageQueue queue

forceListening

protected final boolean forceListening

Constructor Detail

AbstractMessagingService

protected AbstractMessagingService(CdsProperties.Messaging.MessagingServiceConfig serviceConfig,
                                   CdsRuntime runtime)

Method Detail

init

public void init()

Performs the initialization of the messaging service, by initializing the queues and registering the topic subscriptions.

stop

public void stop()

Used to stop the resources allocated by the messaging service, e.g. AMQP connections

createOrUpdateQueuesAndSubscriptions

protected boolean createOrUpdateQueuesAndSubscriptions()

Performs the initialization of the messaging service, by initializing the queues and registering the topic subscriptions.

Returns:

true, if the initialization created queues and/or subscriptions

emit

public void emit(EventContext context)

Specified by:

emit in interface Service

Overrides:

emit in class ServiceDelegator

isCloudEventsFormat

protected boolean isCloudEventsFormat()

emit

public void emit(String topic,
                 String message)

Specified by:

emit in interface MessagingService

emit

public void emit(String topic,
                 Map<String,Object> message)

Specified by:

emit in interface MessagingService

cloudEventsFormatter

@HandlerOrder(value=11000)
protected void cloudEventsFormatter(TopicMessageEventContext context)

sendMessageEvent

@HandlerOrder(value=-9900)
protected void sendMessageEvent(TopicMessageEventContext context)

defaultErrorHandler

@HandlerOrder(value=11000)
protected void defaultErrorHandler(MessagingErrorEventContext context)

on

public void on(String[] events,
               String[] entities,
               int order,
               Handler handler)

Specified by:

on in interface Service

Overrides:

on in class ServiceDelegator

toFullyQualifiedQueueName

protected String toFullyQualifiedQueueName(MessageQueue queue)

Translates the queue name corresponding the broker queue name specification.

Parameters:

queue - queue specification

Returns:

broker environment specific queue name

toFullyQualifiedTopicName

protected String toFullyQualifiedTopicName(String event,
                                           boolean inbound)

Translates the given event definition to the broker environment specific name.

Parameters:

event - event definition

inbound - determines whether topic is used for subscription

Returns:

the list of topic names corresponding the broker environment.

getTopicMatcher

protected BiPredicate<MessageTopic,String> getTopicMatcher()

The topic matcher is used when the broker subscribes to a topic pattern. In this case the implementation is needed to match the incoming message topic to the CAP registered topic pattern (e.g "+/+/+/myTopic" to "my/client/namespace/myTopic").

Returns:

the topic matcher

removeQueue

protected abstract void removeQueue(String name)
                             throws IOException

Request the broker for queue deletion with all its subscriptions.

Parameters:

name - queue name

Throws:

IOException - In case an error occurs while creating the queue

createQueue

protected abstract void createQueue(String name,
                                    Map<String,String> properties)
                             throws IOException

Request the broker for creating a queue with the specified queue name.

Parameters:

name - queue name

properties - queue configuration properties

Throws:

IOException - In case an error occurs while creating the queue

createQueueSubscription

protected abstract void createQueueSubscription(String queue,
                                                String topic)
                                         throws IOException

Requests the broker for creating a queue topic subscription. The method returnstrue only when the queue topic subscription was successfully created or already available. Otherwise false is returned.

Parameters:

queue - the queue name

topic - the topic the queue should subscribe to

Throws:

IOException - In case an error occurs during the subscription

registerQueueListener

protected abstract void registerQueueListener(String queue,
                                              MessagingBrokerQueueListener listener)
                                       throws IOException

Registers the MessagingBrokerQueueListener implementation to the specified queue of the message broker.

Parameters:

queue - the queue name

listener - implementation of the MessagingBrokerQueueListener interface

Throws:

IOException - In case when any errors occurs while registering the listener to the broker

emitTopicMessage

protected abstract void emitTopicMessage(String topic,
                                         TopicMessageEventContext topicMessageEventContext)

Performs the message emit on the messaging broker.

Parameters:

topic - the message topic

topicMessageEventContext - the TopicMessageEventContext of the message