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By Anirban Sen Chowdhary

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Today we will be looking at how to map an inbound properties of a
Mule message with the Message payload

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But before we go forward let’s quickly into what is a Mule Messages and
the structure of a Mule message

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If we look at the Mule message format, we find that Mule message is
generally divided into 3 parts as follows:-
You can see there are basically 3 parts :-
1) Properties :- Outbound or Inbound properties like our query param
2) Payload :- Contains the actual message content
3) Attachment :- It’s optional field may or may not contain attachment
Image source :- Mule Soft

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Now, in our application what ever we send as a query parameter in the
browser comes into our application as inbound properties of Message.
For example if we use the following url in our browser :-
http://localhost:8888/test?id=231&name=Anirban
Here we are sending 2 query parameters id=231&name=Anirban in our
application which will come as an inbound properties in our application

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.

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We can use following MEL expression in our logger to extract the values of
query parameter in our Mule application :-
#[message.inboundProperties['id']] #[message.inboundProperties['name']]
If we put the above expression in a logger :-
<logger message="inbound #[message.inboundProperties['id']]
#[message.inboundProperties['name']]" level="INFO" doc:name="Logger"/>
we will get the following values in our console :-

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Now what if we want to put the query parameter as a part of
Message payload and not as an Inbound properties of Message ???

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Yes, you can easily map an Inbound properties of a Mule Message
with Mule payload by using :-
<http:body-to-parameter-map-transformer/>
This component will transform all the Inbound properties ( query
parameter in our case ) as a part of actual Message payload

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Now, we will see a simple example to know how the component
http:body-to-parameter-map-transformer transform all the
Inbound message properties into actual message payload

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You can see a simple flow, where we have put http:body-to-parameter-
map-transformer after Http inbound endpoint. The main task of this
component will be transforming all the Inbound properties of messages
into the message payload as a hash map of name-value pairs

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The flow in the Mule config will be :-
<flow name="Body-To-Parameter-MapFlow1" doc:name="Body-To-Parameter-MapFlow1">
<http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8888" path="test"
doc:name="HTTP" />
<logger message="inbound #[message.inboundProperties['id']] #[message.inboundProperties['name']]" level="INFO"
doc:name="Logger"/>
<http:body-to-parameter-map-transformer doc:name="Body to Parameter Map"/>
<logger level="INFO" category="Log1" doc:name="Logger" message="#[message.payload['id']]
#[message.payload['name']]"/>
<logger level="INFO" category="Full Message" doc:name="Logger" message="#[message.payload]"/>
</flow>

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The flow in the Mule config will be :-
<flow name="Body-To-Parameter-MapFlow1" doc:name="Body-To-Parameter-MapFlow1">
<http:inbound-endpoint exchange-pattern="request-response" host="localhost" port="8888" path="test"
doc:name="HTTP" />
<logger message="inbound #[message.inboundProperties['id']] #[message.inboundProperties['name']]" level="INFO"
doc:name="Logger"/>
<http:body-to-parameter-map-transformer doc:name="Body to Parameter Map"/>
<logger level="INFO" category="Log1" doc:name="Logger" message="#[message.payload['id']]
#[message.payload['name']]"/>
<logger level="INFO" category="Full Message" doc:name="Logger" message="#[message.payload]"/>
</flow>
As you can see here we have put 2 loggers to check the message payload
content after http:body-to-parameter-map-transformer with the MEL
expression :- #[message.payload['id']] and #[message.payload['name']]
And to check full message payload :- #[message.payload]

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If we check behind the scene what the http:body-to-parameter-map-
transformer is actually doing :-
You can see it’s transforming message properties into payload content

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Now, if we test our application and hit the following url :-
http://localhost:8888/test?id=231&name=Anirban
We will get the following in our console :-
You can see in the log that the query parameters are now part of actual
message payload

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For more information on this http:body-to-parameter-map-transformer
please visit MuleSoft documentation :-
http://www.mulesoft.org/documentation/display/current/HTTP+Transport+R
eference
PS: As of Mule 3.6 and later, the HTTP endpoint-based connector and transport has been
replaced by an operation-based HTTP connector.

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Hope you enjoyed the simple yet an amazing trick in Mule.
And I wish these simple trick would be beneficial for a beginner in
Mule and help him/her in learning and implementing these concepts in
Mule