Registering for Messages Sent to Another Service
A service can register to receive copies of messages that are sent to a specific topic service, as follows:
registerToMessages("MyTopicService");
The service receives all messages sent to it, plus all messages sent to the MyTopicService .
Filtering the Messages
Instead of receiving all messages sent to a topic service, a service can specify that it wants to receive only a subset of messages. To do this, create a SQL WHERE clause (without WHERE ) that specifies which messages to send to the service, and pass this string as a second parameter in registerToMessages() .
The SQL clause can only check predefined parameters in the message sent to the other service. For more information about predefined parameters, see Setting/Getting Parameters .
For example, the following passes all messages whose destination parameter is either A or B :
String selector = "destination IN ('A','B')";
registerToMessages("MyTopicService",selector);
You cannot predict which service will receive the message first.