[Java][Webclient] Unable to deserialize OffsetDateTime

Created by: marcoreni

Description

If we declare a date-time string, the deserialization causes an exception:

Type definition error: [simple type, class java.time.OffsetDateTime]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `java.time.OffsetDateTime` (no Creators, like default construct, exist): no String-argument constructor/factory method to deserialize from String value ('2018-08-27T15:13:30.892Z')

openapi-generator version

3.2.3-SNAPSHOT

OpenAPI declaration file content or url

openapi: 3.0.0

paths:
  /pets:
    get:
      summary: List all pets
      operationId: listPets
      tags:
        - pets
      parameters:
        - name: limit
          in: query
          description: How many items to return at one time (max 100)
          required: false
          schema:
            type: integer
            format: int32
      responses:
        '200':
          description: A paged array of pets
          headers:
          content:
            application/json:    
              schema:
                $ref: "#/components/schemas/Pets"
components:
  schemas:
    Pet:
      required:
        - id
        - name
      properties:
        id:
          type: integer
          format: int64
        name:
          type: string
        lastUpdate:
          type: string
          format: date-time
        tag:
          type: string
    Pets:
      type: array
      items:
        $ref: "#/components/schemas/Pet"

Suggest a fix/enhancement

Jackson jsr310 module is listed as a dependency but it's not registered inside the objectMapper instance.

We should add:

mapper.registerModule(new JavaTimeModule());
mapper.findAndRegisterModules();

during buildWebClient() as stated in https://github.com/FasterXML/jackson-modules-java8#registering-modules (see the warning)

Will submit a PR soon.