Package com.sap.cds.services.messaging

Interface MessagingService

All Superinterfaces:

Service

public interface MessagingService
extends Service

Messaging service.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	COMPOSITE_NAME	The name of the composite MessagingService
static final String	EVENT_MESSAGING_ERROR	The messaging error event, that allows to handle acknowledgement of a message on the messaging channel

Method Summary

Modifier and Type	Method	Description
void	emit(String topic, String message)	If the service is not configured with the structured flag (default), the message is sent to the specified topic of this message broker as is.
void	emit(String topic, Map<String,Object> message)	If the service is not configured with the structured flag (default), the message Map is serialized to JSON and sent to the specified topic of this message broker as is.
void	emit(String topic, Map<String,Object> data, Map<String,Object> headers)	Takes a (cloudevents) message, separated into data and headers and sends it to the specified topic of this message broker.

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

after, after, after, after, before, before, before, before, emit, getName, on, on, on, on

Field Details

COMPOSITE_NAME

static final String COMPOSITE_NAME

The name of the composite MessagingService

See Also:

• Constant Field Values

EVENT_MESSAGING_ERROR

static final String EVENT_MESSAGING_ERROR

The messaging error event, that allows to handle acknowledgement of a message on the messaging channel

See Also:

• Constant Field Values

Method Details

emit

void emit(String topic,
 String message)

If the service is not configured with the structured flag (default), the message is sent to the specified topic of this message broker as is. If the service is configured with the structured flag, the message String is converted into a Map following the rule: {message: message} The Map is then interpreted as data map and passed to emit(String, Map). Usually this results in a final message like: {data: {message: message}}

Parameters:

topic - the topic

message - the message to be sent

emit

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

If the service is not configured with the structured flag (default), the message Map is serialized to JSON and sent to the specified topic of this message broker as is. If the service is configured with the structured flag, the message Map is interpreted as data map and passed to emit(String, Map, Map). Usually this results in a final message like: {data: message}

Parameters:

topic - the topic

message - the Map to be serialized to JSON and then sent

emit

void emit(String topic,
 Map<String,Object> data,
 Map<String,Object> headers)

Takes a (cloudevents) message, separated into data and headers and sends it to the specified topic of this message broker. This method produces the same final message, regardless of the structured flag. Usually data and headers are combined into a final JSON string message following the rule: {...headers, data: data}. Brokers (e.g. Kafka) that do natively support headers are able to separate headers from data, when using this method.

Parameters:

topic - the topic

data - the data Map

headers - the headers Map