Here’s the description of some action items that require analysis during Mule 3 to Mule 4 migration:
- Configuration properties
Definition of loading of properties differs between mule versions.
- HTTP connectors
There are differences in the connector, especially when handling multipart projects.
- Replace MEL with DataWeave
MEL is no longer supported; DataWeave 2.0 is now the expression language.
- Refactor of transformers
Transformers (Ex. <object-to-string />, <object-to-json>) are no longer supported.
- DataWeave 1.0 to 2.0
Syntax and functions differ from 1.0 to 2.0; this requires analysis and translation.
- Object Store
It uses a new connector, which will require changes.
- Exception handling
Mule 4 uses a new system called Error Handlers.
- Message structure
Due to changes in the message structure, attachments, session properties, inbound, outbound, and invocation properties are no longer supported.
- Poll component
In Mule 4, the <poll> element is replaced with the <scheduler> element.
- Java calls
Interoperability with Java is now done through the Java module.
- Spring beans
Instead of defining Spring beans directly in the application, one needs to use the Spring Module.
- Custom Aggregators
In scatter-gather, the java class definition is no longer needed and is replaced by DataWeave.
- Until-Successful component
Properties for configuring this component are changed between versions, requiring refactoring.
Splitters are no longer available in Mule 4. This needs to be refactored and replaced; aggregators have different behavior.
- For Each Scope
In Mule 4, the transformation of the incoming collection to Java is unnecessary.
Filters are no longer available; this needs to be replaced by the Validation Module.
The message enricher is no longer available and is required to be used within each component call using their target parameter.
There are changes in the structure that has been packaged that requires refactoring.
- API kit
Changes to HTTP Listener, Auto discovery configuration, and validation configuration are required.
- Other components that require migration
FTP and SFTP Connector
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