Package org.springframework.integration.jdbc.channel

Class PostgresChannelMessageTableSubscriber

java.lang.Object
org.springframework.integration.jdbc.channel.PostgresChannelMessageTableSubscriber
All Implemented Interfaces:
Lifecycle, Phased, SmartLifecycle
public final class PostgresChannelMessageTableSubscriber extends Object implements SmartLifecycle
A subscriber for new messages being received by a Postgres database via a JdbcChannelMessageStore. This subscriber implementation is using Postgres' LISTEN/NOTIFY mechanism to allow for receiving push notifications for new messages what functions even if a message is written and read from different JVMs or JdbcChannelMessageStores.

Note that this subscriber requires an unshared PgConnection which remains open for any lifecycle. It is therefore recommended to execute a single subscriber for any JVM. For this reason, this subscriber is region-agnostic. To listen for messages for a given region and group id, use a PostgresChannelMessageTableSubscriber.Subscription and register it with this subscriber.

In order to function, the Postgres database that is used must define a trigger for sending notifications upon newly arrived messages. This trigger is defined in the schema-postgresql.sql file within this artifact but commented out.

Since:
6.0
Author:
Rafael Winterhalter, Artem Bilan

  • Constructor Details

    • PostgresChannelMessageTableSubscriber

      public PostgresChannelMessageTableSubscriber(PgConnectionSupplier connectionSupplier)
      Create a new subscriber using the JdbcChannelMessageStore.DEFAULT_TABLE_PREFIX.
      Parameters:
      connectionSupplier - The connection supplier for the targeted Postgres database.

    • PostgresChannelMessageTableSubscriber

      public PostgresChannelMessageTableSubscriber(PgConnectionSupplier connectionSupplier, String tablePrefix)
      Create a new subscriber.
      Parameters:
      tablePrefix - The table prefix of the JdbcChannelMessageStore to subscribe to.
      connectionSupplier - The connection supplier for the targeted Postgres database.

  • Method Details

    • setExecutor

      public void setExecutor(@Nullable ExecutorService executor)
      Define an executor to use for listening for new messages. Note that the Postgres SQL driver implements listening for notifications as a blocking operation which will permanently block a thread of this executor while running.
      Parameters:
      executor - The executor to use or null if an executor should be created by this class.

    • subscribe

      public boolean subscribe(PostgresChannelMessageTableSubscriber.Subscription subscription)
      Add a new subscription to this subscriber.
      Parameters:
      subscription - The subscription to register.
      Returns:
      true if the subscription was not already added.

    • unsubscribe

      public boolean unsubscribe(PostgresChannelMessageTableSubscriber.Subscription subscription)
      Remove a previous subscription from this subscriber.
      Parameters:
      subscription - The subscription to remove.
      Returns:
      true if the subscription was previously registered and is now removed.

    • start

      public void start()
      Specified by:
      start in interface Lifecycle

    • stop

      public void stop()
      Specified by:
      stop in interface Lifecycle

    • isRunning

      public boolean isRunning()
      Specified by:
      isRunning in interface Lifecycle