Mule 3 to Mule 4 migration using Mule Migration Assistant

In this tutorial we will talk about how to migrate the MuleSoft code from Mule 3 to mule 4 using the newly released open source project mule migration assistant (MMA).

Since the launch of Mule 4 (with many benefits) and the end of support for 3.x, there has been an urgent need in every organization to migrate the code from Mule 3.x to Mule 4.x.

You can follow two approach to migrate the old 3.x code to new 4.x code. One is to rewrite the complete code in mule 4, which is not an easy task. Another approach is to use MMA tool to migrate the application from mule 3.x to mule 4.x.

Although MMA does not do the job perfectly, but it eases the migration for you. It also provides you a report of issues, generated during migration, which you would need to correct for the complete migration to 4.x.  If you want to read more on mule Migration Assistant, you can refer to link MMA

Prerequisite

Here are the prerequisite for the Migration.The minimum requirement is version 7.3.0 for Anypoint studio and 4.3 for Mule Runtime.

• Mule Migration Assistant (Zip file)
• Anypoint Studio 6 (external link)
• Anypoint Studio 7 (external link):

Steps for Migration

Here are the steps to migrate the code from Mule 3.x to Mule 4.x.

Open any Mule 3.x project in the Anypoint studio 6.x

Create Mule 4.x project from mule 3.x project USING MMA Tool

Download the MMA zip file and unzip it. Run the command below from the unzipped directory as below.

java -jar mule-migration-assistant-runner-1.0.0.jar -muleVersion 4.3.0 -projectBasePath C:\Users\mulesy\AnypointStudio\workspace6\test-project -destinationProjectBasePath C:\Users\mulesy\AnypointStudio\workspace6\test-project-mule4

After successful execution of the command you would see the result and the new project as below

D:\Application\mule-migration-assistant-runner-1.0.0>java -jar mule-migration-assistant-runner-1.0.0.jar -muleVersion 4.3.0 -projectBasePath C:\Users\mulesy\AnypointStudio\workspace6\test-project -destinationProjectBasePath C:\Users\mulesy\AnypointStudio\workspace6\test-project-mule4
Executing migrator 1.0.0...
===============================================================================
MIGRATION ASSISTANT RUN SUCCESSFULLY
===============================================================================
Total time: 4.861 s
Migration report: C:\Users\mulesy\AnypointStudio\workspace6\test-project-mule4\report\summary.html
D:\Application\mule-migration-assistant-runner-1.0.0>

Open the project in studio 7.3 or higher version

Open the Summary Report for issues

Open the Summary report generated by MMA tool for the issues during the conversion. The report would be created inside the {project}\report\summary.html .The issues are categorized as Errors, Warnings, and Info for classification of the issues. We need to fix these issues before we run the project in 4.3 version.

test-project-mule4\report\summary.html

Click on each issue link to get detail of the issue as below

Steps to resolve the above issues.

• Configure the oracle JDBC driver to fix the first issue. Add the ojdbc dependency to fix this.
• Delete the http status code xml snippet as below.

<http:response statusCode=<em>"#[migration::HttpListener::httpListenerResponseSuccessStatusCode(vars)]"</em>>
<!--Migration WARN: Avoid using an outbound property to determine the status code.-->
<!-- For more information refer to:-->
<!-- * https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/user-docs/migration-tool-post-mig.adoc#outbound_properties-->
<http:headers>#[migration::HttpListener::httpListenerResponseHeaders(vars)]</http:headers>
</http:response>
<http:error-response statusCode=<em>"#[vars.statusCode default migration::HttpListener::httpListenerResponseErrorStatusCode(vars)]"</em>>
<!--Migration WARN: Avoid using an outbound property to determine the status code.-->
<!-- For more information refer to:-->
<!-- * https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/user-docs/migration-tool-post-mig.adoc#outbound_properties-->
<http:headers>#[migration::HttpListener::httpListenerResponseHeaders(vars)]</http:headers>
</http:error-response>

• Delete the “Attributes to inbound properties” as we do not need it

<compatibility:attributes-to-inbound-properties>
<!--Migration WARN: Expressions that query 'inboundProperties' from the message should instead query the message 'attributes'. Remove this component if there are no uses of 'inboundProperties' in expressions or components that rely on 'inboundProperties' (such as 'copy-properties').-->
<!-- For more information refer to:-->
<!-- * https://docs.mulesoft.com/mule-runtime/4.3/intro-mule-message#inbound-properties-are-now-attributes-->
<!-- * https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/user-docs/migration-tool-post-mig.adoc#inbound_properties-->
</compatibility:attributes-to-inbound-properties>

• Delete the “Outbound properties to var” as we do not need it

<compatibility:outbound-properties-to-var>
<!--Migration WARN: Instead of using outbound properties in the flow, move the expression that sets the property into the XML attribute (such as 'method') of the operation or listener that accepts the expression.-->
<!-- For more information refer to:-->
<!-- * https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/user-docs/migration-tool-post-mig.adoc#outbound_properties-->
</compatibility:outbound-properties-to-var>

• Update the “flowVars” to vars

Run the new mule 4.x application.

Once all the issues are resolved. Run the project and it should start seamlessly.

Resources

Here is the project we used for the conversion. We have added both 3.x and converted 4.x project for your reference.

Mule 3.x sample project

Mule 4.x migrated project