[BUG][Java][resttemplate] object that consists only of additionalProperties leads to broken code generation since 7.12.0

[NilsDammenhayn]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

After updating from 7.11.0 to 7.12.0 my code generation breaks. The given example (for me) has two issues:

1. The generated code does not compile anymore. The hashCode-method looks like this return Objects.hash(, additionalProperties);. It does compile as soon as you add at least one parameter to the SampleClass though. Then the hashCode method is correct.
2. The generated class does not extend HashMap<String, Object> anymore but has a parameter called "additionalProperties". I rely on the generated class being a map, which I thought is correct for a schema like that.

openapi-generator version

7.12

OpenAPI declaration file content or url

openapi: 3.1.0
info:
  title: "TEST"
  version: 1.0.0
components:
  schemas:
    SampleObject:
      type: object
      additionalProperties:
        type: object

Generation Details

I'm using Java 21 and Gradle 8.13. Here is my config

{
  "dateLibrary": "java8",
  "useJakartaEe": true,
  "library": "resttemplate",
  "enumPropertyNaming": "legacy",
  "generateAliasAsModel": true
}

When registering the Gradle task I do set globalProperties.set(mapOf("models" to "")) so I only get my model file generated.

Steps to reproduce

• Create the example.yaml above
• Execute the code generation with the provided config
• Compare generated classes in 7.11 and 7.12
  • 7.12 does not compile and does not extend HashMap
  • 7.11 does compile and extends HashMap

Related issues/PRs

I assume that this has to do with this PR #19706 taken from the 7.12's release notes.

Suggest a fix

I'm quite sure this is not supposed to happen like that, as the code does not even compile anymore. Or am I doing something wrong here?

Thank you very much!

[NilsDammenhayn]

@jpfinne Thanks for your response in #20831 to this report!
I'm trying to get my code generation running with the microprofile-library (changed it from resttemplate). Changing to this lib does generate the extends HashMap part, also in 7.12.0 which is nice. But it also seems to ignore the useJakartaEe-flag and generates javax-imports 😕 I tried a few things like changing the generator to java-microprofiles, tested a few different library-configs and so on but I could not find a config that works all the way through: extending HashMap and also using the jakarta-imports. Am I missing something or is that worthy of another bug report? 😅

[jpfinne]

@NilsDammenhayn I'm not familiar with the microfile generator. I only see that it keeps the extends HashMap<>

The use of a Map<String, String> additionalProperties instead of extends HashMap seems justified when there are other properties like in

SampleObject:
  type: object
  properties:
     name:
        type: string
  additionalProperties:
      type: object

Probably less justified for

SampleObject:
  type: object
  additionalProperties:
      type: object

This produces a lot of bugs for generateAliasAsModel=true.
For example invalid hashCode() and invalid default value like

private SampleObject sampleObject = new HashMap<>();

My PR fixes that. It also fixes your compilation error in hashCode()

A third case is inline elements:

MyObject:
  type: object
  properties:
      sampleObject:
        type: object
        additionalProperties:
          type: object

The generated code uses HashMap directly

class MyObject {
    private Map<String, Object> sampleObject = new HashMap<>()

For your use case I would suggest creating a SampleObject.java that fits your need. and configure schemaMapping/typeMapping to use

[NilsDammenhayn]

Okay thanks for your response 🙏 I'll wait for the release of your PR and until then become used to working with the additionalProperties-member I guess 😄

[JoaoBrlt]

Hi @NilsDammenhayn! 👋

Indeed, since v7.12.0, the resttemplate library uses an additionalProperties attribute annotated with @JsonAnySetter and @JsonAnyGetter instead of extending HashMap.
This is because otherwise Jackson is not able to properly serialize and deserialize classes representing schemas that use both properties and additional properties.

Thanks for flagging the issue with the equals and hashCode methods! 👌
My bad, I copied an existing Mustache template code from another java library without considering this situation.

Also, big thanks to @jpfinne for the pull request! 💪

Related issues:

• Serialization - Class extends HashMap FasterXML/jackson-databind#3173
• [java] Combining "properties" and "additionalProperties" in one class generates broken Jackson mapping. #1466
• [BUG] [JAVA] combining properties and additionalProperties generates broken Model class #17361
• [BUG] [JAVA] [restclient] combining properties and additionalProperties generates broken Model class #20853

[jpfinne]

@JoaoBrlt glad to help.

The PR #20902 fixed the issue in resttemplate and restclient. But now there are merge issues.

I'll try another PR

[NilsDammenhayn]

@jpfinne Is there any update on this? ☺️

[jpfinne]

@NilsDammenhayn I ve created #20933
Could you test it?

[NilsDammenhayn]

@jpfinne I'm confused, are you sure that you linked the correct pull request? #20933 does not seem to have to do anything with additionalProperties at first glance and is not authored by you.

[jpfinne]

@NilsDammenhayn sorry, my bad. Forget my message

[kdwink]

Seem like the same, or related, issue occurs for java native clients using generator 7.15.0

    StatusFields:
      description: StatusFields
      type: object
      additionalProperties:
        description: Single map entries
        type: object
        properties:
          code:
            description: code
            type: integer
          text:
            description: text
            type: string

Results in a StatusFields.java class with non-compiling hashCode:

  @Override
  public int hashCode() {
    return Objects.hash(, additionalProperties);
  }