diff --git a/docs/src/reference/docbook/channel.xml b/docs/src/reference/docbook/channel.xml
index e91179d207..aac3439e0f 100644
--- a/docs/src/reference/docbook/channel.xml
+++ b/docs/src/reference/docbook/channel.xml
@@ -377,17 +377,6 @@ public Message receive(final PollableChannel channel) { ... }]]>Publish Subscribe channel, use the <publish-subscribe-channel/> element:
<publish-subscribe-channel id="exampleChannel"/>
-
- To create a Datatype Channel that only
- accepts messages containing a certain payload type, provide the fully-qualified class name in the
- channel element's datatype attribute:
- ]]>
- Note that the type check passes for any type that is assignable to the channel's
- datatype. In other words, the "numberChannel" above would accept messages whose payload is
- java.lang.Integer or java.lang.Double. Multiple types can be
- provided as a comma-delimited list:
- ]]>
-
When using the <channel/> element without any sub-elements, it will create a DirectChannel
instance (a SubscribableChannel).
@@ -419,6 +408,65 @@ public Message receive(final PollableChannel channel) { ... }]]>
+
+ Datatype Channel Configuration
+
+ There are times when a consumer can only process a particular type of payload and you need to ensure the payload type of the input Message.
+ Of course the first thing that comes to mind is Message Filter. However all that Message Filter will do is filter out Messages that are not compliant with
+ the requirements of the consumer. Another way would be to use a Content Based Routing and route Messages with incompliant data-type to specific
+ Transformers to ensure transformation/conversion to the required data-type. This of course would work, but there is a simpler way of accomplishing this if
+ you apply Datatype Channel pattern.
+ You can use separate Datatype Channel for a specific data-type of the payload.
+
+
+ To create a Datatype Channel that only
+ accepts messages containing a certain payload type, provide the fully-qualified class name in the
+ channel element's datatype attribute:
+
+ ]]>
+
+ Note that the type check passes for any type that is assignable to the channel's
+ datatype. In other words, the "numberChannel" above would accept messages whose payload is
+ java.lang.Integer or java.lang.Double. Multiple types can be
+ provided as a comma-delimited list:
+ ]]>
+
+
+ So the 'numberChannel' above will only accept Messages with data-type of java.lang.Number regardless of what was
+ the payload type of the Message that was sent to this channel. But what happens if the payload of the Message is not of the required type?
+ In this case the Datatype Channel will attempt to convert the type of the payload to the required type using Spring's
+ Conversion Service where
+ you can register custom converters. For example:
+
+
+ Let's say you are sending a Message with a String payload to the 'numberChannel' we configured above.
+ ("5"));
+ ]]>
+
+ Typically this would be a perfectly legal operation, however since we are using Datatype Channel the result of such operation will be exception:
+
+
+ And rightfully so since we are requiring the payload type to be a Number while sending a String. So we need something to convert String to a Number.
+All we need to do is implement a Converter
+ {
+ public Integer convert(String source) {
+ return Integer.parseInt(source);
+ }
+}]]>
+Register it as a converter with Integration Conversion Service
+
+
+]]>
+And now the send operation will be successful since our Datatype Channel will use this converter to convert String to Integer.
+
+
+
QueueChannel Configuration