Mule messages contain a header and payload. The header includes properties and variables that provide metadata about the message. Properties have inbound and outbound scopes, while variables have flow, session, and application scopes. Transformers can change the type, content, or properties of a message. Splitters break messages into parts that are routed to different endpoints. Aggregators reassemble split messages using correlation properties. Resequencers reorder messages that were processed out of order to put them back in the correct sequence.

1. Mule ESB –Advanced

2. Mule Message Structure
 The Mule message is the data that passes through an application via one or
more flows. It consists of two main parts:
 The message header, which contains metadata about the message
 The message payload, which contains your business-specific data.

3. Mule Message Properties and Variables
 Message header consists of properties which
provide useful information about the message
 variables represent data about a message
 Properties have two main
scopes: inbound and outbound.Inbound Property

4. Mule Message Variables
 Variables are user-defined metadata about a
message.
 Variables have three scopes:
Flow variables apply only to the flow in which
they exist.
Session variables apply across all flows within the
same application.

6. Outbound Endpoint
Mapping message headers to transport headers

7. Mapping transport headers to message headers
Inbound Endpoint

8. Transformation Types
 3 Types of Transformers
Type transformation - involves converting the ‘type’ of the
message, for example; converting a byte stream to a string or
converting a JMS Message to a Java object.
Message transformation involves converting the message itself,
for example; converting a BookingRequest object into an
AirlineTicket object.
Property Transformations involves the properties on a message.
Each message may contain properties, usually related to
the transport used. For example, a message sent to an SMTP
server would have ‘To’, ‘From’ and ‘CC’ properties

9. SPLITTER
 A message splitter can be used to break down an outgoing message
into parts and dispatch those parts over different endpoints configured
on the router.

10. SplitterExample
<flow name="SplitterExampleFlow1" doc:name="SplitterExampleFlow1">
<http:inbound-endpoint exchange-pattern="request-response"
host="localhost" port="8081" doc:name="HTTP"/>
<splitter expression="#[xpath('//actor')]" doc:name="Splitter"
enableCorrelation="IF_NOT_SET"/>
<logger message="#[message.payload]" level="INFO"
doc:name="Logger"/>
</flow>

11. Mule Aggregator
Mule aggregators use the MULE_CORRELATION_ID and
MULE_CORRELATION_GROUP_SIZE to reassemble a split
message.

12. <flow name="aggregateLineItems">
<jms:inbound-endpoint queue="lineitem.complete“ connector-
ref="jmsConnector"/>
<collection-aggregator timeout="60000“ failOnTimeout="true" />
<custom-transformer
class="com.prancingdonkey.transformer.LineItemsToOrderTransformer"/
>
<component
class="com.prancingdonkey.service.OrderProcessingService"/>
</flow>
Mule Aggregator Example

13. Resequencer
If fractions of the message are being processed in
parallel in different servers, there's a good chance
that they may take different lengths of time to be
processed, and consequently fall out of order.

14.  The Resequencer will wait for all of the messages in
the group to arrive (keeping track
of MULE_CORRELATION_ID and
MULE_CORRELATION_GROUP_SIZE )
 Reorder them according to their
MULE_CORRELATION_SEQUENCE index.
 The Resequencer outputs will be in distinct
messages,