The document discusses how to map inbound message properties in Mule to the message payload using the http:body-to-parameter-map-transformer. It explains that Mule messages have properties, payload, and attachments. Properties contain things like query parameters. The transformer allows moving properties, like query parameters, into the payload. An example shows query parameters in the properties, then using the transformer to put them in the payload instead. Checking the logs confirms the parameters are now in the payload after transforming.

1. By Anirban Sen Chowdhary

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

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

4. 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

5. 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

6. .

7. 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 :-

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

9. 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

10. 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

11. 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

12. 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>

13. 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]

14. 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

15. 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

16. 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.

17. 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