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.
public
CachedMessageQueue(String name, MessagingCapabilities capabilities)
- name: String - (optional) queue name
- capabilities: MessagingCapabilities - (optional) capabilities of the message queue
Fields
Abstract methods
subscribe
Subscribes to the message broker.
public abstract
void subscribe(IContext context)
- context: IContext - (optional) a context to trace execution through a call chain.
unsubscribe
Unsubscribes from the message broker.
public abstract
void unsubscribe(IContext context)
- context: IContext - (optional) a context to trace execution through a call chain.
Instance methods
clear
Clears component state.
public
void clear(IContext context)
- context: IContext - (optional) a context to trace execution through a call chain.
configure
Configures a component by passing its configuration parameters.
public
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.
public
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
public
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.
public
void 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.
public
MessageEnvelope peek(IContext context) throws InvalidStateException
- context: IContext - (optional) a context to trace execution through a call chain.
- returns: Promise<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.
public
List<MessageEnvelope> peekBatch(IContext context, int messageCount) throws InvalidStateException
- context: IContext - (optional) a context to trace execution through a call chain.
- messageCount: int - maximum number of messages to peek.
- returns: List<MessageEnvelope> - list with peeked messages.
readMessageCount
Reads the current number of messages in the queue to be delivered.
public
int readMessageCount()
- returns: int - number of messages in the queue.
receive
Receives an incoming message and removes it from the queue.
public
MessageEnvelope receive(IContext context, long waitTimeout) throws InvalidStateException
- context: IContext - (optional) a context to trace execution through a call chain.
- waitTimeout: long - timeout in milliseconds to wait for a message to come.
- returns: MessageEnvelope - received message or null.
sendMessageToReceiver
Sends a message to a receiver.
protected
void sendMessageToReceiver(IMessageReceiver receiver, MessageEnvelope message)
- receiver: IMessageReceiver - receiver of the message.
- message: MessageEnvelope - message to be sent.