INT-3557 Clarify MessageHeaders Constants
JIRA: https://jira.spring.io/browse/INT-3557 Add class names and code tags. Add missing header constants. Polishing for `timestamp` header doc. Fix JavaDocs issues: https://build.spring.io/browse/INT-EIGHTAPI-296
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Gary Russell
committed by
Artem Bilan
Artem Bilan
parent
0cc9273a2e
commit
0f568c0526
@@ -63,30 +63,39 @@
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The following Message headers are pre-defined:
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<table id="message-headers-table">
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<title>Pre-defined Message Headers</title>
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<tgroup cols="2">
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<tgroup cols="3">
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<colspec align="left" />
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<thead>
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<row>
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<entry align="center">Header Name</entry>
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<entry align="center">Header Type</entry>
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<entry align="center">Usage</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>ID</entry>
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<entry>java.util.UUID</entry>
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<entry><code>MessageHeaders.ID</code></entry>
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<entry><code>java.util.UUID</code></entry>
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<entry>An identifier for this message instance. Changes each time a message is mutated.</entry>
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</row>
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<row>
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<entry>TIMESTAMP</entry>
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<entry>java.lang.Long</entry>
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<entry><code>MessageHeaders.TIMESTAMP</code></entry>
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<entry><code>java.lang.Long</code></entry>
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<entry>The time the message was created. Changes each time a message is mutated.</entry>
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</row>
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<row>
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<entry>REPLY_CHANNEL</entry>
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<entry>java.lang.Object (can be a String or MessageChannel)</entry>
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<entry><code>MessageHeaders.REPLY_CHANNEL</code></entry>
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<entry><code>java.lang.Object</code> (String or MessageChannel)</entry>
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<entry>A channel to which a reply (if any) will be sent when no explicit output
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channel is configured and there is no <code>ROUTING_SLIP</code> or the
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<code>ROUTING_SLIP</code> is exhausted. If the value is a <code>String</code>
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it must represent a bean name, or have been generated by a <classname>ChannelRegistry.</classname></entry>
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</row>
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<row>
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<entry>ERROR_CHANNEL</entry>
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<entry>java.lang.Object (can be a String or MessageChannel)</entry>
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<entry><code>MessageHeaders.ERROR_CHANNEL</code></entry>
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<entry><code>java.lang.Object</code> (String or MessageChannel)</entry>
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<entry>A channel to which errors will be sent. If the value is a <code>String</code>
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it must represent a bean name, or have been generated by a <classname>ChannelRegistry.</classname></entry>
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</row>
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</tbody>
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</tgroup>
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@@ -94,59 +103,108 @@
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</para>
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<para>
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Many inbound and outbound adapter implementations will also provide and/or expect certain headers, and additional
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user-defined headers can also be configured.
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user-defined headers can also be configured. Constants for these headers can be found in those modules where such
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headers exist, for example <classname>AmqpHeaders</classname>, <classname>JmsHeaders</classname> etc.
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</para>
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<section id="message-header-accessor">
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<title>MessageHeaderAccessor API</title>
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<para>
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Since Spring Framework 4.0 and Spring Integration 4.0, the core Messaging abstraction has been moved to
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Starting with Spring Framework 4.0 and Spring Integration 4.0, the core Messaging abstraction has been moved to
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the <emphasis>spring-messaging</emphasis> module and the new <classname>MessageHeaderAccessor</classname> API
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has been introduced to provide additional abstraction over Messaging implementations. All Spring
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has been introduced to provide additional abstraction over Messaging implementations. All (core) Spring
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Integration specific Message Headers constants are now declared in the
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<classname>IntegrationMessageHeaderAccessor</classname>:
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<classname>IntegrationMessageHeaderAccessor</classname> class:
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<table id="integration-message-headers-table">
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<title>Pre-defined Message Headers</title>
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<tgroup cols="2">
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<tgroup cols="3">
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<colspec align="left" />
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<thead>
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<row>
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<entry align="center">Header Name</entry>
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<entry align="center">Header Type</entry>
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<entry align="center">Usage</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>CORRELATION_ID</entry>
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<entry>java.lang.Object</entry>
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<entry><code>IntegrationMessageHeaderAccessor.CORRELATION_ID</code></entry>
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<entry><code>java.lang.Object</code></entry>
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<entry>Used to correlate two or more messages.</entry>
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</row>
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<row>
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<entry>SEQUENCE_NUMBER</entry>
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<entry>java.lang.Integer</entry>
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<entry><code>IntegrationMessageHeaderAccessor.SEQUENCE_NUMBER</code></entry>
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<entry><code>java.lang.Integer</code></entry>
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<entry>Usually a sequence number with a group of messages with a
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<code>SEQUENCE_SIZE</code> but can also
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be used in a <code><resequencer/> to resequence an unbounded
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group of messages.</code></entry>
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</row>
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<row>
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<entry>SEQUENCE_SIZE</entry>
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<entry>java.lang.Integer</entry>
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<entry><code>IntegrationMessageHeaderAccessor.SEQUENCE_SIZE</code></entry>
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<entry><code>java.lang.Integer</code></entry>
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<entry>The number of messages within a group of correlated messages.</entry>
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</row>
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<row>
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<entry>EXPIRATION_DATE</entry>
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<entry>java.lang.Long</entry>
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<entry><code>IntegrationMessageHeaderAccessor.EXPIRATION_DATE</code></entry>
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<entry><code>java.lang.Long</code></entry>
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<entry>Indicates when a message is expired. Not used by the framework directly
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but can be set with a header enricher and used in a <code><filter/></code>
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configured with an <classname>UnexpiredMessageSelector</classname>.</entry>
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</row>
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<row>
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<entry>PRIORITY</entry>
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<entry>java.lang.Integer</entry>
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<entry><code>IntegrationMessageHeaderAccessor.PRIORITY</code></entry>
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<entry><code>java.lang.Integer</code></entry>
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<entry>Message priority; for example within a <classname>PriorityChannel</classname></entry>
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</row>
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<row>
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<entry><code>IntegrationMessageHeaderAccessor.DUPLICATE_MESSAGE</code></entry>
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<entry><code>java.lang.Boolean</code></entry>
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<entry>True if a message was detected as a duplicate by an idempotent receiver
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interceptor. See <xref linkend="idempotent-receiver" />.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para>
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Convenient typed getters for these headers are provided on the
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Convenient typed getters for some of these headers are provided on the
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<classname>IntegrationMessageHeaderAccessor</classname> class:
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<programlisting language="java"><![CDATA[IntegrationMessageHeaderAccessor accessor = new IntegrationMessageHeaderAccessor(message);
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int sequenceNumber = accessor.getSequenceNumber();
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Object correlationId = accessor.getCorrelationId();
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...]]></programlisting>
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</para>
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<para>
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The following headers also appear in the
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<classname>IntegrationMessageHeaderAccessor</classname> but are generally not used by
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user code; their inclusion here is for completeness:
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<table id="extra-integration-message-headers-table">
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<title>Pre-defined Message Headers</title>
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<tgroup cols="3">
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<colspec align="left" />
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<thead>
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<row>
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<entry align="center">Header Name</entry>
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<entry align="center">Header Type</entry>
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<entry align="center">Usage</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><code>IntegrationMessageHeaderAccessor.SEQUENCE_DETAILS</code></entry>
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<entry><code>java.util.List< List<Object>></code></entry>
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<entry>A stack of correlation data used when nested correlation is needed (e.g. <code>
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splitter->...->splitter->...->aggregator->...->aggregator</code>).</entry>
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</row>
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<row>
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<entry><code>IntegrationMessageHeaderAccessor.ROUTING_SLIP</code></entry>
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<entry><code>java.util.Map< List<Object>, Integer></code></entry>
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<entry>See <xref linkend="routing-slip" />.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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</section>
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<section id="message-id-generation">
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<title>Message ID Generation</title>
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