DeliveryMode (Java EE 5)

如果客户端感觉若该消息在传输中丢失，应用程序就会发生问题，它就将消息标记为持久。如果偶然丢失消息是可容忍的，则客户端将消息标记为非持久。客户端使用传送模式告知 JMS 提供者如何在消息传输可靠性和吞吐量之间保持平衡。

传送模式仅包含消息到其目的地的传输。PERSISTENT 传送模式不保证在确认消息接收者之前将消息保留在目的地。客户端应该假定已通过管理方式设置了消息保留策略。消息保留策略管理从目的地到消息使用方的消息传送的可靠性。例如，如果客户端的消息存储空间已耗尽，则依据特定于站点的消息保留策略，某些消息可能被丢弃。

如果消息的传送模式是 PERSISTENT 并且如果目的地有充分的消息保留策略，则可以保证消息由 JMS 提供者传送一次并且只传送一次。

The delivery modes supported by the JMS API are PERSISTENT and NON_PERSISTENT.

A client marks a message as persistent if it feels that the application will have problems if the message is lost in transit. A client marks a message as non-persistent if an occasional lost message is tolerable. Clients use delivery mode to tell a JMS provider how to balance message transport reliability with throughput.

Delivery mode covers only the transport of the message to its destination. Retention of a message at the destination until its receipt is acknowledged is not guaranteed by a PERSISTENT delivery mode. Clients should assume that message retention policies are set administratively. Message retention policy governs the reliability of message delivery from destination to message consumer. For example, if a client's message storage space is exhausted, some messages may be dropped in accordance with a site-specific message retention policy.

A message is guaranteed to be delivered once and only once by a JMS provider if the delivery mode of the message is PERSISTENT and if the destination has a sufficient message retention policy.

Version:

1.0 - 7 August 1998

Author:

Mark Hapner, Rich Burridge

英文文档：

NON_PERSISTENT

static final int NON_PERSISTENT

This is the lowest-overhead delivery mode because it does not require that the message be logged to stable storage. The level of JMS provider failure that causes a NON_PERSISTENT message to be lost is not defined.

A JMS provider must deliver a NON_PERSISTENT message with an at-most-once guarantee. This means that it may lose the message, but it must not deliver it twice.

See Also:

Constant Field Values

英文文档：

PERSISTENT

static final int PERSISTENT

This delivery mode instructs the JMS provider to log the message to stable storage as part of the client's send operation. Only a hard media failure should cause a PERSISTENT message to be lost.

See Also:

Constant Field Values

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