com.r3corda.core.messaging

## Package com.r3corda.core.messaging

### Types

Ack | `object Ack : DeserializeAsKotlinObjectDef` A general Ack message that conveys no content other than its presence for use when you want an acknowledgement from a recipient. Using Unit can be ambiguous as it is similar to Void and so could mean no response.
AllPossibleRecipients | `interface AllPossibleRecipients : MessageRecipients` A special base class for the set of all possible recipients, without having to identify who they all are.
Message | `interface Message` A message is defined, at this level, to be a (topic, timestamp, byte arrays) triple, where the topic is a string in Java-style reverse dns form, with "platform." being a prefix reserved by the platform for its own use. Vendor specific messages can be defined, but use your domain name as the prefix e.g. "uk.co.bigbank.messages.SomeMessage".
MessageHandlerRegistration | `interface MessageHandlerRegistration`
MessageRecipientGroup | `interface MessageRecipientGroup : MessageRecipients` A base class for a set of recipients specifically identified by the sender.
MessageRecipients | `interface MessageRecipients` The interface for a group of message recipients (which may contain only one recipient)
MessagingService | `interface MessagingService` A MessagingService sits at the boundary between a message routing / networking layer and the core platform code.
MessagingServiceBuilder | `interface MessagingServiceBuilder<out T : MessagingService>` This class lets you start up a MessagingService. Its purpose is to stop you from getting access to the methods on the messaging service interface until you have successfully started up the system. One of these objects should be the only way to obtain a reference to a MessagingService. Startup may be a slow process: some implementations may let you cast the returned future to an object that lets you get status info.
SingleMessageRecipient | `interface SingleMessageRecipient : MessageRecipients` A base class for the case of point-to-point messages
TopicStringValidator | `object TopicStringValidator` A singleton thats useful for validating topic strings

### Functions

runOnNextMessage | `fun MessagingService.runOnNextMessage(topic: String = "", executor: Executor? = null, callback: (Message) -> Unit): Unit` Registers a handler for the given topic that runs the given callback with the message and then removes itself. This is useful for one-shot handlers that arent supposed to stick around permanently. Note that this callback doesnt take the registration object, unlike the callback to MessagingService.addMessageHandler.
send | `fun MessagingService.send(topic: String, payload: Any, to: MessageRecipients): Unit`