Browse

Browsing messages

The browse source streams the messages in a queue without consuming them.

Unlike the other sources, the browse source will complete after browsing all the messages currently on the queue.

Scala

copysource
val browseSource: Source[javax.jms.Message, NotUsed] = JmsConsumer.browse(
  JmsBrowseSettings(system, connectionFactory)
    .withQueue("test")
)

val result: Future[immutable.Seq[javax.jms.Message]] =
  browseSource.runWith(Sink.seq)

Java

copysourceConnectionFactory connectionFactory = server.createConnectionFactory();

Source<javax.jms.Message, NotUsed> browseSource =
    JmsConsumer.browse(
        JmsBrowseSettings.create(system, connectionFactory).withQueue("test"));

CompletionStage<List<javax.jms.Message>> result =
    browseSource.runWith(Sink.seq(), system);

A JMS selector can be used to filter the messages. Otherwise it will browse the entire content of the queue.

Notes:

• Messages may be arriving and expiring while the scan is done.
• The JMS API does not require the content of an enumeration to be a static snapshot of queue content. Whether these changes are visible or not depends on the JMS provider.
• A message must not be returned by a QueueBrowser before its delivery time has been reached.

Configure JMS browse

To connect to the JMS broker, first define an appropriate javax.jms.ConnectionFactory. The Alpakka tests and all examples use Active MQ.

Scala

copysourceval connectionFactory: javax.jms.ConnectionFactory = new org.apache.activemq.ActiveMQConnectionFactory(url)

Java

copysourcejavax.jms.ConnectionFactory connectionFactory = server.createConnectionFactory();

The created ConnectionFactory is then used for the creation of the different JMS sources.

The JmsBrowseSettings factories allow for passing the actor system to read from the default alpakka.jms.browse section, or you may pass a Config instance which is resolved to a section of the same structure.

Scala

copysourceval browseConfig: Config = system.settings.config.getConfig(JmsBrowseSettings.configPath)
val settings = JmsBrowseSettings(browseConfig, connectionFactory)
  .withQueue("target-queue")
  .withCredentials(Credentials("username", "password"))
  .withConnectionRetrySettings(retrySettings)

Java

copysourceConfig consumerConfig = config.getConfig(JmsConsumerSettings.configPath());
JmsConsumerSettings settings =
    JmsConsumerSettings.create(consumerConfig, new ActiveMQConnectionFactory("broker-url"))
        .withTopic("message-topic")
        .withCredentials(Credentials.create("username", "password"))
        .withConnectionRetrySettings(retrySettings)
        .withSessionCount(10)
        .withAcknowledgeMode(AcknowledgeMode.AutoAcknowledge())
        .withSelector("Important = TRUE");

The Alpakka JMS browse soruce is configured via default settings in the HOCON config file section alpakka.jms.browse in your application.conf, and settings may be tweaked in the code using the withXyz methods. On the second tab the section from reference.conf shows the structure to use for configuring multiple set-ups.

Table

Setting	Description	Default Value
connectionFactory	Factory to use for creating JMS connections	Must be set in code
destination	The queue to browse	Must be set in code
credentials	JMS broker credentials	Empty
connectionRetrySettings	Retry characteristics if the connection failed to be established or is taking a long time.	See Connection Retries

reference.conf

copysource# Jms Browse Settings
# sets default values
browse {
  # Configure connection retrying by providing settings for ConnectionRetrySettings.
  connection-retry = ${alpakka.jms.connection-retry}
  # Credentials to connect to the JMS broker.
  # credentials {
  #   username = "some text"
  #   password = "some text"
  # }
  # "off" to not use any credentials.
  credentials = off
  # JMS selector expression.
  # See https://docs.oracle.com/cd/E19798-01/821-1841/bncer/index.html
  # empty string for unset
  selector = "" # optional
  # Set an explicit acknowledge mode.
  # See eg. javax.jms.Session.AUTO_ACKNOWLEDGE
  # Allowed values: "auto", "client", "duplicates-ok", "session", integer value
  acknowledge-mode = auto
}