AWS API Proxy decodes multi-value query parameter into a comma-separated string

[bivapa]

Expected Behavior

When I send a multi-value query parameter as part of an x-www-form-urlencoded Lambda Gateway request, I expect it to be decoded in the controller as a collection of values — just like it is in standard server mode (micronaut-http-server-netty), e.g. ["foo", "bar"].

Actual Behaviour

When I send a multi-value query parameter as part of an x-www-form-urlencoded Lambda Gateway request, it is decoded into a comma-separated string, e.g. "foo,bar".

Steps To Reproduce

• Clone the example application
• Run ./mvnw -P server clean test
• The test ExampleServerControllerTest.testMultiValueQueryParameter will pass under the Netty based configuration ✅
• Run ./mvnw -P serverless clean test
• The equivalent test ExampleServerlessControllerTest.testMultiValueQueryParameter will fail ❌ under the AWS API Proxy configuration

Environment Information

Java 17

Example Application

https://github.com/bivapa/micronaut-serverless-multi-value-query-bug-report

Version

4.8.2