Mule 3 to Mule 4 Migration Cheat Sheet

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.

  • Splitter/Aggregator

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

Filters are no longer available; this needs to be replaced by the Validation Module.

  • Enrichers

The message enricher is no longer available and is required to be used within each component call using their target parameter.

  • Policies

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

File Connector

Email Connector

AMQP Connector

FTP and SFTP Connector

Database Connector

Scripting Connector

Validation Connector

VM Connector


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