[BUG] serializableModel generates "extends" instead of "implements"

[thorstenhirsch]

Bug Report Checklist

Description

When generating Java code with serializableModel=true the result is faulty.

expected result:

public class MyClass implements Serializable {
}

current result (simplified):

public class MyClass extends Serializable {
}

In my case there was already an class from which to extend, so Serializable was just added:
current result:

public class MyClass extends Something, Serializable {
}

openapi-generator version

7.3.0 with Java 17 and Java 21

OpenAPI declaration file content or url & Generation Details

Just use any OpenAPI JSON with the following command to generate the Java code:

java -jar libs/openapi-generator-cli-7.3.0.jar generate \
      -i ./my.json -g java -o genc \
      --additional-properties library=native,serializableModel=true

Steps to reproduce

1. Generate code
2. Check classes for "Serializable"

[martin-mfg]

Hi,
in my tests with your described settings, it worked fine. Here's an example of the output I get: public class MyObject extends HashMap<String, Object> implements Serializable {.
If the problem persists for you, please provide a minimal reproducible example.

[thorstenhirsch]

Just reproduced the issue with version 7.4.0. You can use the attached Test-OpenAPI.json to reproduce the issue. With the following call you will get a class de.my.client.model.CoreBar with a faulty Serializable declaration.

$ java -jar openapi-generator-cli-7.4.0.jar generate -i ./Test-OpenAPI.json -g java -o genc --additional-properties library=native,serializableModel=true --invoker-package=de.my.client --model-package=de.my.client.model --api-package=de.my.client.api

public class CoreBar extends AbstractOpenApiSchema, Serializable { ... }

P.S.: Java version = 21, platform = Windows 10.

Test-OpenAPI.json

[thorstenhirsch]

I could break down the problem to this parameter:

library=native

Without this parameter the generator works correctly.

[martin-mfg]

Thanks for the clarification. I could reproduce the issue now and created a fix for it.