This document discusses different routing techniques in Mule such as splitters, aggregators, filters, for each scopes, and main flows vs sub flows. For each scopes split a collection into elements and process them iteratively, returning the original message. Main flows accept message sources while sub flows only accept processors, and can be called via flow references. Filters filter messages using expressions, and expression filters check conditions while message filters throw exceptions if the condition is not met.

1. Mule Expression Routing
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2. Routing
 The Routing module reviews the different types of Routers and how
Routers are used to control how messages are sent and received by
components. The message can be route in different ways. Below are
explained in this example.
• Splitters and Aggregators
• Collection splitter and Collection Aggregator
• Message chunk splitter and Message chunk aggregator
• Scatter gather
• For each
• Mule flows, Sub flows and flow reference
• Filters

3. For Each:
 The Foreach scope splits a collection into elements and processes
them iteratively through the processors embedded in the scope, then
returns the original message to the flow.

4.  As For Each expects a collection object is expected a java component
is used to generate a List object.
 Above properties are available in for each scope. Collection field which
accepts MEL to provide a collection object to the for each component
for iteration. Counter Variable Name is a variable which stores the
count of iterations. Batch Size is partition the Collection into sub
collections of the specified size. Root Message Variable Name holds
the message before being split.

5. Main Flow, Sub Flow and Flow reference:
 A mule flow (main flow) which accepts message source and message
processor where sub flow accepts only message processor. Sub flow
can be called via flow reference because it doesn't accept messag
source.
 Sub flow runs completely in the same context of the flow that calls it,
inheriting transcation context, exception handler, all variables and
headers, etc.
 A Main flow has its own context, transcation context, exception
handler, all variables and headers etc.

7. Filters:
 Filters are used to filter the message using mule expressions.
 Above flow accepts a HTTP request and filters the message using
Expression filter and also throws an exception if Expression filter is
not satisfied using Message Filter.

8.  Expression Filter allows you to right a Mule Expression. if the
expression returns true then the process continuous to next message
processor. or else the flow get discarded without throwing any
exception. Here the condition is checking for payload instance is
java.util.List or not.

9.  If we need to throw an exception when Expression Filter returns false,
then Expression filter needs wrapped up the Message Filter and
throwOnUnaccecpted attribute should be true as shown in below
snippet.

10. Thank You All