This document summarizes different routing techniques in Mule including splitters, aggregators, for each scopes, main flows, sub flows, and filters. It explains that for each scopes split a collection into elements and process them iteratively, sub flows can be called via flow reference and inherit context from the calling flow, and filters like expression filters can route messages conditionally and optionally throw exceptions if the filter is not satisfied.
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
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.
6.
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.
