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Updated core-api

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This commit is contained in:
Mark Fisher
2008-10-15 02:30:55 +00:00
parent d5b0f380f7
commit ea2bb3e7c7
1 changed files with 14 additions and 16 deletions
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30
spring-integration-reference/src/core-api.xml
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@@ -31,7 +31,7 @@
<tbody>
<row>
<entry>ID</entry>
<entry>java.lang.Object</entry>
<entry>java.util.UUID</entry>
</row>
<row>
<entry>TIMESTAMP</entry>
@@ -39,19 +39,15 @@
</row>
<row>
<entry>EXPIRATION_DATE</entry>
<entry>java.util.Date</entry>
<entry>java.lang.Long</entry>
</row>
<row>
<entry>CORRELATION_ID</entry>
<entry>java.lang.Object</entry>
</row>
<row>
<entry>NEXT_TARGET</entry>
<entry>java.lang.Object (can be a String or MessageTarget)</entry>
</row>
<row>
<entry>RETURN_ADDRESS</entry>
<entry>java.lang.Object (can be a String or MessageTarget)</entry>
<entry>java.lang.Object (can be a String or MessageChannel)</entry>
</row>
<row>
<entry>SEQUENCE_NUMBER</entry>
@@ -70,7 +66,7 @@
</table>
</para>
<para>
Many source and target adapter implementations will also provide and/or expect certain headers, and additional
Many inbound/outbound adapter implementations will also provide and/or expect certain headers, and additional
user-defined headers can also be configured.
</para>
<para>
@@ -79,13 +75,13 @@
<programlisting language="java">new GenericMessage&lt;T&gt;(T payload);
new GenericMessage&lt;T&gt;(T payload, Map&lt;String, Object&gt; headers)</programlisting>
When a Message is created, a random unique id will be generated. The constructor that accepts a Map of headers
will copy the provided headers to the newly created Message. There are also two convenient subclasses available
currently: <classname>StringMessage</classname> and <classname>ErrorMessage</classname>. The latter accepts any
will copy the provided headers to the newly created Message. There are also two convenient subclasses available:
<classname>StringMessage</classname> and <classname>ErrorMessage</classname>. The latter accepts any
<classname>Throwable</classname> object as its payload.
</para>
<para>
You may notice that the Message interface defines retrieval methods for its payload and headers but no setters.
This is fully intentional so that each Message is unmodifiable after creation. Therefore, when a Message
The reason for this is that a Message cannot be modified after its initial creation. Therefore, when a Message
instance is sent to multiple consumers (e.g. through a Publish Subscribe Channel), if one of those consumers
needs to send a reply with a different payload type, it will need to create a new Message. As a result, the
other consumers are not affected by those changes. Keep in mind, that multiple consumers may access the same
@@ -156,10 +152,10 @@ assertEquals(MessagePriority.HIGHEST, anotherMessage.getHeaders().getPriority())
<para>
The <interfacename>Message</interfacename> is obviously a very important part of the API. By encapsulating the
data in a generic wrapper, the messaging system can pass it around without any knowledge of the data's type. As
the system evolves to support new types, or when the types themselves are modified and/or extended, the messaging
system will not be affected by such changes. On the other hand, when some component in the messaging system
<emphasis>does</emphasis> require access to information about the <interfacename>Message</interfacename>, such
metadata can typically be stored to and retrieved from the metadata in the Message Headers.
an application evolves to support new types, or when the types themselves are modified and/or extended, the
messaging system will not be affected by such changes. On the other hand, when some component in the messaging
system <emphasis>does</emphasis> require access to information about the <interfacename>Message</interfacename>,
such metadata can typically be stored to and retrieved from the metadata in the Message Headers.
</para>
</section>
@@ -221,8 +217,10 @@ target.send(new StringMessage("test"));</programlisting>
While the <interfacename>Message</interfacename> plays the crucial role of encapsulating data, it is the
<interfacename>MessageChannel</interfacename> that decouples message producers from message consumers.
Spring Integration's top-level <interfacename>MessageChannel</interfacename> interface is defined as follows.
<programlisting language="java"><![CDATA[public interface MessageChannel extends MessageSource, BlockingTarget {
<programlisting language="java"><![CDATA[public interface MessageChannel {
String getName();
boolean send(Message message);
}]]></programlisting>
Because it extends <interfacename>BlockingTarget</interfacename>, it inherits the following methods:
<programlisting language="java">boolean send(Message message);