java - 为顺序子流调用选择适当的 EIP

Question

在Spring Integration我需要按顺序将消息发送到子流 A(它将消息存储到数据库中)，然后再发送到子流 B(它使用一些数据库查找)。整个 A 和 B 执行应该在一个事务的边界内执行。

最初，Publish-Subscribe Channel在一个线程中使用了 A 和 B 的 2 个订阅者。但是，有两个缺点

1. 没有保证订阅者执行的顺序
2. 很容易添加task-executor channel 的属性。因此，A 和 B 将在不同的线程中并行执行，从而在不同的事务中执行。

那么，什么EIP用在这里比较好？

我在考虑Recipient List Router但是，再一次，can't see guaranty收件人的消息发送顺序。

Answer 1

AbstractMessageHandler 上有一个order 属性，它保证订阅者将如何订阅到PublishSubscribeChannel:http://docs.spring.io/spring-integration/reference/html/messaging-channels-section.html#channel-implementations-directchannel :

The order is determined by an optional order value defined on the handlers themselves or, if no such value exists, the order in which the handlers are subscribed.

If a certain situation requires that the dispatcher always try to invoke the first handler, then fallback in the same fixed order sequence every time an error occurs, no load-balancing strategy should be provided. In other words, the dispatcher still supports the failover boolean property even when no load-balancing is enabled. Without load-balancing, however, the invocation of handlers will always begin with the first according to their order. For example, this approach works well when there is a clear definition of primary, secondary, tertiary, and so on. When using the namespace support, the "order" attribute on any endpoint will determine that order.

还有AbstractDispatcher的源代码:

private final OrderedAwareCopyOnWriteArraySet<MessageHandler> handlers =
        new OrderedAwareCopyOnWriteArraySet<MessageHandler>();

还有一个 order XML 属性描述:

    <xsd:attribute name="order" type="xsd:string">
        <xsd:annotation>
            <xsd:documentation><![CDATA[
Specifies the order for invocation when this endpoint is connected as a
subscriber to a channel. This is particularly relevant when that channel
is using a "failover" dispatching strategy. It has no effect when this
endpoint itself is a Polling Consumer for a channel with a queue.

                ]]></xsd:documentation>
        </xsd:annotation>
    </xsd:attribute>