Extends: MessageQueue
Implements: ICleanable
Description
The CachedMessageQueue class allows you to create message queues that cache received messages in memory, to allow peek operations that may not be supported by the undelying queue.
Important points
- This queue is used as a base implementation for other queues.
Constructors
Creates a new instance of the persistence component.
CachedMessageQueue(String? name, MessagingCapabilities? capabilities)
- name: String? - (optional) queue name
- capabilities: MessagingCapabilities? - (optional) capabilities of the message queue
Fields
Instance methods
clear
Clears component state.
@override
Future<void> clear(IContext? context): Promise<void>
- context: IContext - (optional) a context to trace execution through a call chain.
configure
Configures a component by passing its configuration parameters.
@override
void configure(ConfigParams config)
- config: ConfigParams - configuration parameters to be set.
endListen
Ends listening for incoming messages. When this method is called, listen unblocks the thread and execution continues.
void endListen(IContext? context)
- context: IContext - (optional) a context to trace execution through a call chain.
listen
Listens for incoming messages and blocks the current thread until the queue is closed. See IMessageReceiver, receive
@override
void listen(IContext? context, IMessageReceiver receiver)
- context: IContext - (optional) a context to trace execution through a call chain.
- receiver: IMessageReceiver - receiver used to receive incoming messages.
open
Opens the component.
@override
Future open(IContext? context)
- context: IContext - (optional) a context to trace execution through a call chain.
peek
Peeks a single incoming message from the queue without removing it. If there are no messages available in the queue it returns null.
@override
Future<MessageEnvelope?> peek(IContext? context)
- context: IContext - (optional) a context to trace execution through a call chain.
- returns: Future<MessageEnvelope?> - peeked message or null.
peekBatch
Peeks multiple incoming messages from the queue without removing them. If there are no messages available in the queue it returns an empty list.
Important: This method is not supported by MQTT.
@override
Future<List<MessageEnvelope?» peekBatch(IContext? context, int messageCount)
- context: IContext - (optional) a context to trace execution through a call chain.
- messageCount: int - maximum number of messages to peek.
- returns: Future<List<MessageEnvelope?» - list with peeked messages.
readMessageCount
Reads the current number of messages in the queue to be delivered.
@override
Future<int> readMessageCount()
- returns: Future<int> - number of messages in the queue.
receive
Receives an incoming message and removes it from the queue.
@override
Future<MessageEnvelope?> receive(IContext? context, int waitTimeout)
- context: IContext - (optional) a context to trace execution through a call chain.
- waitTimeout: int - timeout in milliseconds to wait for a message to come.
- returns: Future<MessageEnvelope?> - received message or null.
sendMessageToReceiver
Sends a message to a receiver.
Future sendMessageToReceiver(IMessageReceiver? receiver, MessageEnvelope? message)
- receiver: IMessageReceiver? - receiver of the message.
- message: MessageEnvelope? - message to be sent.
subscribe
Subscribes to the message broker.
Future subscribe(IContext? context)
- context: IContext - (optional) a context to trace execution through a call chain.
unsubscribe
Unsubscribes from the message broker.
Future unsubscribe(IContext? context)
- context: IContext - (optional) a context to trace execution through a call chain.