QualityOfServiceMode (ActiveMQ Artemis Web 1.1.0.wildfly-010 API)
Date: 2015-12-18

org.apache.activemq.artemis.jms.bridge

## Enum QualityOfServiceMode

- java.lang.Object
- - java.lang.Enum<QualityOfServiceMode>
  - - org.apache.activemq.artemis.jms.bridge.QualityOfServiceMode

- All Implemented Interfaces:
    Serializable, Comparable<QualityOfServiceMode>

      public enum QualityOfServiceMode
      extends Enum<QualityOfServiceMode>

  ### Quality of server (QoS) levels

  #### QOS_AT_MOST_ONCE

  With this QoS mode messages will reach the destination from the source at most once. The messages are consumed from the source and acknowledged before sending to the destination. Therefore there is a possibility that if failure occurs between removing them from the source and them arriving at the destination they could be lost. Hence delivery will occur at most once. This mode is available for both persistent and non persistent messages.

  #### QOS_DUPLICATES_OK

  With this QoS mode, the messages are consumed from the source and then acknowledged after they have been successfully sent to the destination. Therefore there is a possibility that if failure occurs after sending to the destination but before acknowledging them, they could be sent again when the system recovers. I.e. the destination might receive duplicates after a failure. This mode is available for both persistent and non persistent messages.

  #### QOS_ONCE_AND_ONLY_ONCE

  This QoS mode ensures messages will reach the destination from the source once and only once. (Sometimes this mode is known as "exactly once"). If both the source and the destination are on the same ActiveMQ Artemis server instance then this can be achieved by sending and acknowledging the messages in the same local transaction. If the source and destination are on different servers this is achieved by enlisting the sending and consuming sessions in a JTA transaction. The JTA transaction is controlled by JBoss Transactions JTA implementation which is a fully recovering transaction manager, thus providing a very high degree of durability. If JTA is required then both supplied connection factories need to be XAConnectionFactory implementations. This mode is only available for persistent messages. This is likely to be the slowest mode since it requires extra persistence for the transaction logging. Note: For a specific application it may possible to provide once and only once semantics without using the QOS_ONCE_AND_ONLY_ONCE QoS level. This can be done by using the QOS_DUPLICATES_OK mode and then checking for duplicates at the destination and discarding them. Some JMS servers provide automatic duplicate message detection functionality, or this may be possible to implement on the application level by maintaining a cache of received message ids on disk and comparing received messages to them. The cache would only be valid for a certain period of time so this approach is not as watertight as using QOS_ONCE_AND_ONLY_ONCE but may be a good choice depending on your specific application.

- - ### Enum Constant Summary

    Enum Constants
    Enum Constant and Description
    `AT_MOST_ONCE`
    `DUPLICATES_OK`
    `ONCE_AND_ONLY_ONCE`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `intValue()`
    `static QualityOfServiceMode` | `valueOf(int value)`
    `static QualityOfServiceMode` | `valueOf(String name)` Returns the enum constant of this type with the specified name.
    `static QualityOfServiceMode[]` | `values()` Returns an array containing the constants of this enum type, in the order they are declared.

    - ### Methods inherited from class java.lang.Enum

      `clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf`

    - ### Methods inherited from class java.lang.Object

      `getClass, notify, notifyAll, wait, wait, wait`

- - ### Enum Constant Detail

    - #### AT_MOST_ONCE

          public static final QualityOfServiceMode AT_MOST_ONCE

    - #### DUPLICATES_OK

          public static final QualityOfServiceMode DUPLICATES_OK

    - #### ONCE_AND_ONLY_ONCE

          public static final QualityOfServiceMode ONCE_AND_ONLY_ONCE

  - ### Method Detail

    - #### values

          public static QualityOfServiceMode[] values()

      Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

          for (QualityOfServiceMode c : QualityOfServiceMode.values())
              System.out.println(c);

      Returns:
        an array containing the constants of this enum type, in the order they are declared

    - #### valueOf

          public static QualityOfServiceMode valueOf(String name)

      Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
      Parameters:
        `name` - the name of the enum constant to be returned.
      Returns:
        the enum constant with the specified name
      Throws:
        `IllegalArgumentException` - if this enum type has no constant with the specified name
        `NullPointerException` - if the argument is null

    - #### intValue

          public int intValue()

    - #### valueOf

          public static QualityOfServiceMode valueOf(int value)

Copyright © 2015. All rights reserved.