Message History
消息构建体系的主要优点在于松散耦合，以至于参与组件不会维护彼此之间的任何感知。仅这一事实就使应用程序极其灵活，它使你可以更改组件而不影响其余流程、更改消息路由、更改消息消费样式（轮询与事件驱动），等等。但是，当出现问题时，这种不起眼的体系构建样式可能会被证明是困难的。在调试时，或许你需要尽可能多的关于消息的信息（其来源、它已遍历过的通道及其他详细信息）。
The key benefit of a messaging architecture is loose coupling such that participating components do not maintain any awareness about one another. This fact alone makes an application extremely flexible, letting you change components without affecting the rest of the flow, change messaging routes, change message consuming styles (polling versus event driven), and so on. However, this unassuming style of architecture could prove to be difficult when things go wrong. When debugging, you probably want as much information (its origin, the channels it has traversed, and other details) about the message as you can get.
消息历史记录是一种模式，它可以通过让你可以选择维护消息路径的某些级别的感知来帮助你，该模式用于调试或维护审计跟踪。Spring 集成提供了一种简单的方法来配置你的消息流程，以通过向消息添加头并每次消息通过跟踪组件时更新头来维护消息历史记录。
Message history is one of those patterns that helps by giving you an option to maintain some level of awareness of a message path either for debugging purposes or for maintaining an audit trail. Spring integration provides a simple way to configure your message flows to maintain the message history by adding a header to the message and updating that header every time a message passes through a tracked component.
Message History Configuration
若要启用消息历史记录，你仅需要在配置中定义 message-history 元素（或 @EnableMessageHistory），如下例所示：
To enable message history, you need only define the message-history element (or @EnableMessageHistory) in your configuration, as shown in the following example:
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Java
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XML
@Configuration
@EnableIntegration
@EnableMessageHistory<int:message-history/>现在，每个命名组件（已定义“id”）都被跟踪。框架在消息中设置"history"头。其值一个 List<Properties>。
Now every named component (that has an 'id' defined) is tracked.
The framework sets the 'history' header in your message.
Its value a List<Properties>.
考虑以下配置示例：
Consider the following configuration example:
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Java
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XML
@MessagingGateway(defaultRequestChannel = "bridgeInChannel")
public interface SampleGateway {
...
}
@Bean
@Transformer(inputChannel = "enricherChannel", outputChannel="filterChannel")
HeaderEnricher sampleEnricher() {
HeaderEnricher enricher =
new HeaderEnricher(Collections.singletonMap("baz", new StaticHeaderValueMessageProcessor("baz")));
return enricher;
}<int:gateway id="sampleGateway"
service-interface="org.springframework.integration.history.sample.SampleGateway"
default-request-channel="bridgeInChannel"/>
<int:header-enricher id="sampleEnricher" input-channel="enricherChannel" output-channel="filterChannel">
<int:header name="baz" value="baz"/>
</int:header-enricher>前面的配置生成一个简单的消息历史记录结构，具有类似于以下内容的输出：
The preceding configuration produces a simple message history structure, with output similar to the following:
[{name=sampleGateway, type=gateway, timestamp=1283281668091},
{name=sampleEnricher, type=header-enricher, timestamp=1283281668094}]若要获取对消息历史记录的访问权限，你只需访问 MessageHistory 头。以下示例展示了如何执行此操作：
To get access to message history, you need only access the MessageHistory header.
The following example shows how to do so:
Iterator<Properties> historyIterator =
message.getHeaders().get(MessageHistory.HEADER_NAME, MessageHistory.class).iterator();
assertTrue(historyIterator.hasNext());
Properties gatewayHistory = historyIterator.next();
assertEquals("sampleGateway", gatewayHistory.get("name"));
assertTrue(historyIterator.hasNext());
Properties chainHistory = historyIterator.next();
assertEquals("sampleChain", chainHistory.get("name"));你可能不想跟踪所有组件。若要根据名称将历史记录限制为某些组件，你可以提供 tracked-components 属性并指定与你要跟踪的组件匹配的组件名称和模式的逗号分隔列表。以下示例展示了如何执行此操作：
You might not want to track all the components.
To limit the history to certain components based on their names, you can provide the tracked-components attribute and specify a comma-delimited list of component names and patterns that match the components you want to track.
The following example shows how to do so:
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Java
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XML
@Configuration
@EnableIntegration
@EnableMessageHistory("*Gateway", "sample*", "aName")<int:message-history tracked-components="*Gateway, sample*, aName"/>在前面的示例中，仅跟踪以“Gateway”结尾、以“sample”开头或与名称“aName”完全匹配的组件的消息历史记录。
In the preceding example, message history is maintained only for the components that end with 'Gateway', start with 'sample', or match the name, 'aName', exactly.
此外，MessageHistoryConfigurer bean 现在由 IntegrationMBeanExporter 作为 JMX MBean 公开（请参见 MBean Exporter），以便在运行时更改模式。但是，请注意，必须停止 bean（关闭消息历史记录）才能更改模式。此功能可能有助于暂时开启历史记录以分析系统。MBean 的对象名称是 <domain>:name=messageHistoryConfigurer,type=MessageHistoryConfigurer。
In addition, the MessageHistoryConfigurer bean is now exposed as a JMX MBean by the IntegrationMBeanExporter (see MBean Exporter), letting you change the patterns at runtime.
Note, however, that the bean must be stopped (turning off message history) in order to change the patterns.
This feature might be useful to temporarily turn on history to analyze a system.
The MBean’s object name is <domain>:name=messageHistoryConfigurer,type=MessageHistoryConfigurer.
在应用程序上下文中，仅必须声明一个 @EnableMessageHistory（或 <message-history/>）作为组件跟踪配置的单一来源。不要对 MessageHistoryConfigurer 使用通用 Bean 定义。
Only one @EnableMessageHistory (or <message-history/>) must be declared in the application context as single source for components tracking configuration.
Do not use a generic bean definition for the MessageHistoryConfigurer.
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在版本 6.3 之前，消息历史记录头部是不可变的（你无法重写历史记录）：不仅仅是每个创建的轨道的新 |
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Prior to version 6.3, the message history header was immutable (you cannot re-write history): every single track created not only new instance of the |