Filters in Mule determine whether a message can proceed in a flow. There are 12 bundled filters including Expression and Payload filters that are often used to filter messages. Filters can also apply boolean logic and nest other filters for complex conditions. Custom filters can be created and global filters defined for reuse across flows. For example, filters can be added to airline flows to prevent messages when there are no flights, and ensure payloads are Array Lists for multicast results.

1. Filters

2. What is a Filter?
Determine whether a message can proceed in a Mule flow
By default, filtered messages are dropped and processing of the
message ends
• Keeps subsequent processors from receiving irrelevant or incomprehensible
messages
• Filters can be configured to throw an exception

3. Available Filters
There are 12 bundled filters
• Expression and Payload are often used
• And, Or, Not apply Boolean logic
• Message filter nests other filters for more complex
logical conditions
• Idempotent ensures a message
is not delivered more than once
You can create custom filters
You can define global filters and reference them for reuse

4. Filter Message Example
Add filters to the airline flows to keep them from returning messages when there are no
flights in the payload
Filter the results in the multicast to ensure they are Array Lists
Will be needed when the payload is set to an error message when an exception is thrown in
the next module
Use the Expression and Payload filters
Create and use a global filter