Class AmqpTransport

java.lang.Object

com.codename1.backend.messaging.MessageTransport

com.codename1.backend.messaging.PollingTransport

com.codename1.backend.messaging.amqp.AmqpTransport

All Implemented Interfaces:

Closeable, AutoCloseable

public final class AmqpTransport
extends PollingTransport

Messaging over RabbitMQ, or any AMQP 0-9-1 broker, with no client library.

cn1.messaging.url=amqp://app:secret@rabbit:5672/%2F

A destination is a durable queue of that name, declared on first use and published to through the default exchange, persistent and with publisher confirms: send(Message) returns once the broker has the message. Every listener of a queue competes for its messages, whatever its group says -- a fan-out to several groups is an exchange the application binds itself.

A subscription is one connection consuming with a prefetch equal to its concurrency, so the broker holds back what no consumer thread is free to take; one reader thread receives deliveries and the consumer threads acknowledge each after its handler returns. A message whose handler failed waits in <queue>.retry.<millis>, a queue whose time to live dead-letters it back to the original, so a retry occupies no consumer while it waits. One that fails every attempt goes to <queue>.dlq.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	AmqpTransport.Factory	Registers this transport with Messaging; the generated wiring does it.

Nested classes/interfaces inherited from class PollingTransport

PollingTransport.Delivery

Field Summary

Fields inherited from class PollingTransport

retry

Constructor Summary

Constructors

Constructor	Description
AmqpTransport(String url, RetryPolicy retry, int timeoutMillis)	A transport to the broker url names; it connects on first use.

Method Summary

Modifier and Type	Method	Description
protected void	ack(String destination, String group, PollingTransport.Delivery delivery)	Acknowledges a handled delivery.
void	close()	Stops every subscription and closes the connection.
String	getName()	The scheme this transport was opened for: memory, db, redis, amqp, kafka.
boolean	isHealthy()	Whether the broker answers, for the health endpoint.
protected List<PollingTransport.Delivery>	poll(String destination, String group, int max, long waitMillis)	Up to max messages of destination for group, waiting up to waitMillis for the first; an empty list when none came.
protected void	redeliver(String destination, String group, PollingTransport.Delivery delivery, int attempt, long notBefore)	Has delivery delivered again, as attempt, no sooner than notBefore.
void	send(Message message)	Sends message.
Subscription	subscribe(String destination, String group, int concurrency, MessageHandler handler)	Starts concurrency consumers of destination in group.

Methods inherited from class PollingTransport

deadLetter, identified, notYet, stopSubscriptions

Methods inherited from class MessageTransport

isTransactional

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

AmqpTransport

public AmqpTransport(String url,
 RetryPolicy retry,
 int timeoutMillis)

A transport to the broker url names; it connects on first use.

Method Details

getName

public String getName()

Description copied from class: MessageTransport

The scheme this transport was opened for: memory, db, redis, amqp, kafka.

Specified by:

getName in class MessageTransport

send

public void send(Message message)
          throws IOException

Description copied from class: MessageTransport

Sends message. With a database transport inside a transaction the message is written in that transaction and is seen only if it commits.

Specified by:

send in class MessageTransport

Throws:

IOException

redeliver

protected void redeliver(String destination,
 String group,
 PollingTransport.Delivery delivery,
 int attempt,
 long notBefore)
                  throws IOException

Description copied from class: PollingTransport

Has delivery delivered again, as attempt, no sooner than notBefore. The default sends a copy carrying the attempt and the time in its headers and acknowledges the original; a consumer that polls the copy early puts it back with PollingTransport.notYet(Message, long).

Overrides:

redeliver in class PollingTransport

Throws:

IOException

subscribe

public Subscription subscribe(String destination,
 String group,
 int concurrency,
 MessageHandler handler)
                       throws IOException

Description copied from class: MessageTransport

Starts concurrency consumers of destination in group.

• group: subscriptions of one group share the messages between them, and each group sees every message -- on a transport with groups (Redis Streams, Kafka, AMQP through one queue per group). On memory: and db: a destination is a queue and every subscription competes for it.

Overrides:

subscribe in class PollingTransport

Throws:

IOException

poll

protected List<PollingTransport.Delivery> poll(String destination,
 String group,
 int max,
 long waitMillis)
                                        throws IOException

Description copied from class: PollingTransport

Up to max messages of destination for group, waiting up to waitMillis for the first; an empty list when none came.

Specified by:

poll in class PollingTransport

Throws:

IOException

ack

protected void ack(String destination,
 String group,
 PollingTransport.Delivery delivery)
            throws IOException

Description copied from class: PollingTransport

Acknowledges a handled delivery.

Specified by:

ack in class PollingTransport

Throws:

IOException

isHealthy

public boolean isHealthy()

Description copied from class: MessageTransport

Whether the broker answers, for the health endpoint. Never throws.

Overrides:

isHealthy in class MessageTransport

close

public void close()

Description copied from class: MessageTransport

Stops every subscription and closes the connection. Never throws.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class MessageTransport