To foster enterprise’s efforts in total digital transformation, MuleSoft latest version, the Mule 4 release, is offering some interesting API-led connectivity and integration solutions at a low cost and in a simplified way compared to its prior version, Mule 3 release.
If you are planning to migrate from Mule 3 to Mule 4, here we discuss what is so special about Mule 4 migration, why migrating to Mule 4 is more beneficial, and what the differences are between the Mule 3 and the Mule 4 releases.
Mule 4 Advantages: Why Upgrade from Mule 3 to Mule 4?
1. Integrated and Effective Error Handling
In contrast to the Mule 3 exception of handling, which is based on Java, the Mule 4 error handling framework enables direct handling by having integrated and configurable error handling mechanisms. These mechanisms are where errors are located and handled - based on their type during the design phase itself. In Mule 4, throwing errors is done by validators, not through Java exceptions.
Mule 4 has introduced a new “Try” to get hold of errors of any number of event processes during the flow itself, thereby evading the need for the creation of another flow. This way, Mule 4 ensures uninterrupted and smooth processing flow with a better ability to handle errors.
Learn about Error Handling in MuleSoft Mule 4
2. Better Application Configuration: Maven
To bring improved abilities in configuring and managing application development processes, Mule 4 has come with profound integration with Maven by ensuring all the Mule 4 applications are Maven applications by default (Mule 3 to offer this just has an option to build a Maven project). MuleSoft has changed the overall application structure of Mule 4. Refer to the below image for the application structure of the Mule 4.
Figure: Mule4 Application Structure
Learn about Mule Maven implementation.
3. Simplified Event Processing and Messaging
Figure: Mule 4 Vs Mule 3 Event structure
MuleSoft latest version, Mule 4, brings a more compact event processing model by optimizing unwanted hierarchies and workflows. There is a huge difference between the Mule 3 vs Mule 4 message structure. In the message section of Mule 4 event architecture, the inbound and outbound properties in Mule 3 are merged under one category “Attributes” and this holds the payload’s metadata information, any file content, updates on file, query parameters, flow's message source, inbound properties, outbound properties, and message processor info.
Unlike in Mule 3, the Mule 4 payload itself allows piggybacking attachments to optimize the flow. In Mule 4 events, creation happens whenever changes are made to Mule events. This avoids data discrepancies across all the threads running or other events relying on this event.
In Mule 3, the messages are embedded within the Mule message objects (containing variable, attachment, and exception payloads), and metadata holds information about the message. As a part of message passing, messages are to be transformed explicitly into Java objects, whereas in Mule 4 it happens by default.
Learn about event processing and messaging implementation.
4. DataWeave 2.0 For Better Data Handling
In Mule 3 releases, developers are to use Mule Expression Language (MEL) as well as DataWeave for developing Mule messages. But this approach had some data inconsistencies and scattered approaches. To derive steadiness and streamline data activities, DataWeave 2.0 was launched. DataWeave 2.0 pushes Mule 4 messages right into a connector, rather than using MEL. To have greater data transparency, Mule 4 stores the event structures and responses (data and context).
In contrast to Mule 3, Mule 4 DataWeave avoids the stress of converting data objects to Java objects by the usage of expressions. DataWeave avoids caching data in memory while providing access to data to memory or any data repositories. This way data is streamed fast and transparently and avoids unnecessary memory lags.
Learn about DataWeave2.0 and its implementation.
Differences between Mule 3 and Mule 4
Here are the top differences between Mule 3 and Mule 4 versions.
| Feature | Mule 3 | Mule 4 |
| Data Transformation | Used Mule Expression Language (MEL) for data transmission. | Replaced MEL with DataWeave 2.0 for secure data transmission. |
| Flow Structure | Had error-prone flow structure. | A simplified flow structure with readable syntax for easier management. |
| Error Handling | Error-handling is complex to manage and implement changes. | Offers a robust error handling framework that enables easier identification and resolution of issues during design and development. |
| Event Processing Model | The message structure of Mule 3 is complex. | Provides a streamlined event processing model where the event contains a message and variables, making event processing simple. |
| Batch Processing | Involved Input, Load and Dispatch, Process, and On Complete phases. Making it challenging for developers to understand the different phases involved in processing. | Eliminating the need for record variables and making the batch processing faster and easier. |
| Performance and Scalability | Eliminating the need for record variables and making the batch processing faster and easier. Due to its architectural limitations, Mule 3 imposes bottlenecks when handling multiple requests or large payloads. | Auto-tuning and optimized event processing models contribute to faster processing times and improved performance & scalability. |
| Development Experience | Need deep understanding of code elements. | Faster onboarding and easier configuration. |
How to Migrate from Mule 3 to Mule 4?
Organizations should implement best practices for Mule 4 migration. Here is a step-by-step procedure for a successful Mule 3 to Mule 4 migration.
- Set up MMA: Download the Mule Migration Assistant (MMA) tool from GitHub or through Anypoint Studio.
- Ready with Mule 3 App: Ensure you have an existing Mule 3 application or create one in Anypoint Studio or download from Exchange.
- Import Mule 3 Project: Import the Mule 3 application into Anypoint Studio 6.
- Execute MMA: Run the MMA tool, defining the paths, including the Mule 3 project path and a desired location where you want to migrate the project.
- Report Analysis: Analyze the report generated by the MMA tool, which highlights areas that require manual review and adjustments.
- Java 17: Ensure Java 17 is installed.
- Manual Migration: Based on the report, address the identified issues in the migrated Mule 4 application manually. Refactor expressions, update connectors, adjust configurations, etc.
- Mule 4 Testing: Test the migrated application to ensure its functionality and update environment-specific configurations for the Mule 4 project.
- Performance Monitoring: Monitor the application's performance and behavior and optimize as needed.
Recommended To Read: How to Enable HTTPS Authentication in Mule 4: Step-by-Step Guide
What is the Latest MuleSoft Version?
The latest major version of Mule runtime is 4.9, specifically 4.9.0, released in February 2025. It’s a part of MuleSoft's new release cadence, which includes both Edge and Long Term Support (LTS) versions. On the compatibility front, Mule 4.9.0 supports Java 17 apps and auto-minor upgrades between Mule 4.8 Edge and 4.9 Edge and 4.6 LTS and 4.9 LTS.
Keen to know more technical details about how Mule 4 variants foster the development process over Mule 3 releases? Or, want to know about a step-by-step process for Mule 3 to Mule 4 migration? Then get a free consultation from our MuleSoft experts.
FAQs
- What is Mule Upgrade?
Mule Upgrade is a command line interface tool that updates and upgrades standalone applications of the Mule 4 runtime engine.
- Is It Important to Migrate from Mule 3 to Mule 4?
Yes, as a Certified MuleSoft Consulting Partner, we highly recommend you switch from Mule 3 to Mule 4 to ensure a future-proof integration platform. Migration helps organizations to avoid potential security risks, compatibility issues, poor performance, scalability issues, hidden bugs, poor event processing, and etc.
- Do we need to buy any licenses from MuleSoft to migrate from Mule 3 to Mule 4?
No. You can access limited features accessibility with Mule 3 licenses for Mule 4 applications. But having a Mule 4 license is a good choice for optimal support and long-term ROI.
