[BUG] [Java] javax.annotation.Nullable or javax.annotation.Nonnull on getters in java client

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

I use nullable: false attribute on my properties, but they still annotated with @javax.annotation.Nullable in java code. Is it bug? Or may be I am doing something wrong?

openapi-generator version

5.3.1

OpenAPI declaration file content or url

yaml

openapi: 3.0.3

info:
  title: title
  description: description
  version: LATEST

paths:
  /api/get:
    post:
      summary: getInfo
      operationId: get
      requestBody:
        content:
          application/json:
            schema:
              properties:
                ids:
                  type: array
                  nullable: false
                  items:
                    type: integer
                    format: int64
                    example: 172
      responses:
        '200':
          description: Ok

client.json

{
  "library": "apache-httpclient",
  "openApiNullable": false
}

Generation Details

docker run --rm -v "${PWD}:/local" openapitools/openapi-generator-cli:v5.3.1 generate \
 -i /local/openapi/conf.yaml \
 -c /local/openapi/client.json \
 -g java \
 -o /local/openapi/out

Steps to reproduce

1. Create folder openapi
2. Put client.json in ./openapi/client.json
3. Put conf.yaml in /openapi/conf.yaml
4. Generate output (see command above)
5. Open file openapi/out/src/main/java/org/openapitools/client/model/GetRequest.java

Actual behaviour:
Getter (getIds()) has @Nullable annotation

Expected:
Getter (getIds()) has @Nonnull annotation according to nullable attribute in openapi.yaml configuration.

Suggest a fix

If property is annotated with nullable: true, then annotate getter with @Nullable, otherwise @Nonnull

Reproduce Java client generation with the supplied OpenAPI YAML, client.json, and v5.3.1 command, then inspect openapi/out/src/main/java/org/openapitools/client/model/GetRequest.java. Trace how the ids property's nullable setting affects the generated getIds() annotation. Done means nullable properties produce the expected @Nullable or @Nonnull getter annotation.