[BUG] Missing Java Bean Validation annotations when using `allOf` instead of $ref directly

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 search 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

When using:

components:
  schemas:
    Name:
      type: string
      maxLength: 50
      minLength: 1
      description: "A name"
    Cat:
      type: object
      description: "A cat with a name"
      properties:
        name:
          allOf:
            - $ref: '#/components/schemas/Name'
          description: "Name of this cat"
          example: "Kitty"

The generated code is:

@ApiModelProperty(example = "Kitty", value = "Name of this cat") 
public String getName() {
   return name;
}

Instead of:

@ApiModelProperty(example = "Kitty", value = "Name of this cat")
@Size(min=1,max=50) 
public String getName() {
   return name;
}

openapi-generator version

OpenAPI Generator 4.3.1 and 5.0.0-alpha.

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: My animal API
  version: "1.0"
servers:
  - url: https://api.example.com
paths:
  /cats/:
    post:
      operationId: createCat
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Cat'
      responses:
        201:
          description: ""
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Cat'
  /dogs/:
    post:
      operationId: createDog
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Dog'
      responses:
        201:
          description: ""
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Dog'
components:
  schemas:
    Name:
      type: string
      maxLength: 50
      minLength: 1
      description: "A name"
    Cat:
      type: object
      description: "A cat with a name"
      properties:
        name:
          allOf:
            - $ref: '#/components/schemas/Name'
          description: "Name of this cat"
          example: "Kitty"
    Dog:
      type: object
      description: "A dog with a name"
      properties:
        name:
          allOf:
            - $ref: '#/components/schemas/Name'
          description: "Name of this dog"
          example: "Fido"

Generation Details

Plugin configuration:

<plugin>
    <groupId>org.openapitools</groupId>
    <artifactId>openapi-generator-maven-plugin</artifactId>
    <version>4.3.1</version>
    <executions>
        <execution>
            <id>code-from-openapi-document</id>
            <goals>
                <goal>generate</goal>
            </goals>
            <configuration>
                <inputSpec>${project.basedir}/src/main/resources/spec.yaml</inputSpec>
                <generatorName>spring</generatorName>
                <library>spring-boot</library>
                <apiPackage>com.acme.animals.controller</apiPackage>
                <modelPackage>com.acme.animals.dto</modelPackage>
                <generateApis>true</generateApis>
                <configOptions>
                    <interfaceOnly>true</interfaceOnly>
                    <dateLibrary>java8</dateLibrary>
                    <enableBuilderSupport>true</enableBuilderSupport>
                    <skipDefaultInterface>true</skipDefaultInterface>
                    <performBeanValidation>true</performBeanValidation>
                </configOptions>
            </configuration>
        </execution>
    </executions>
</plugin>

Steps to reproduce

1. Run mvn clean generate-sources
2. The generated classes contain:

  @ApiModelProperty(example = "Kitty", value = "Name of this cat")
  public String getName() {
    return name;
  }

[tommyb82]

We have just encountered this issue (or a very closely related one) via the Maven plugin, openapi-generator-maven-plugin v5.1.1 & 5.2.0 - Spring generator. We are missing the @Pattern annotation (and example attribute in @ApiModelProperty) on the agreementID property in our generated AgreementDetails class, where pattern is specified on the referenced base simple type AgreementId, e.g.

    AgreementId:
      type: string
      pattern: RM[0-9]{4}(.[0-9]{1,2})?
      example: RM1234
      readOnly: true

    AgreementDetails:
      type: object
      properties:
        agreementID:
          allOf:
            - $ref: '#/components/schemas/AgreementId'
          readOnly: false

[robertc-dat]

Still seeing this issue with OpenAPI Generator 5.2.0