JsonIgnore using Open API spec

Question

I use OpenAPI spec to generate Java POJOs. What do I need to specify in Open API yaml to generate the equivalent of below POJO ?

...
@JsonIgnore
public String ignoredProperty;
...

I have the yaml spec as below

openapi: 3.0.0
info:
  title: Cool API
  description: A Cool API spec
  version: 0.0.1
servers:
  - url: http://api.cool.com/v1
    description: Cool server for testing
paths:
  /
  ...
components:
  schemas:
    MyPojo:
      type: object
      properties:
        id:
          type: integer
        name:
          type: string
        # I want the below attribute to be ignored as a part of JSON 
        ignoreProperty:  
          type: string  

Answer 1

the openapi generator supports vendor extensions. Specifically, for the Java generator, it supports the following extensions as of the time of writing. However, an up-to-date list can be found here.

Extension name	Description	Applicable for	Default value
x-discriminator-value	Used with model inheritance to specify value for discriminator that identifies current model	MODEL
x-implements	Ability to specify interfaces that model must implements	MODEL	empty array
x-setter-extra-annotation	Custom annotation that can be specified over java setter for specific field	FIELD	When field is array & uniqueItems, then this extension is used to add @JsonDeserialize(as = LinkedHashSet.class) over setter, otherwise no value
x-tags	Specify multiple swagger tags for operation	OPERATION	null
x-accepts	Specify custom value for 'Accept' header for operation	OPERATION	null
x-content-type	Specify custom value for 'Content-Type' header for operation	OPERATION	null
x-class-extra-annotation	List of custom annotations to be added to model	MODEL	null
x-field-extra-annotation	List of custom annotations to be added to property	FIELD	null
x-webclient-blocking	Specifies if method for specific operation should be blocking or non-blocking(ex: return Mono<T>/Flux<T> or return T/List<T>/Set<T> & execute .block() inside generated method)	OPERATION	false

You can use the x-field-extra-annotation vendor extension listed above to add annotations to any field. So, for your example, you can add the following:

openapi: 3.0.0
info:
  title: Cool API
  description: A Cool API spec
  version: 0.0.1
servers:
  - url: http://api.cool.com/v1
    description: Cool server for testing
paths:
  /
  ...
components:
  schemas:
    MyPojo:
      type: object
      properties:
        id:
          type: integer
        name:
          type: string
        # I want the below attribute to be ignored as a part of JSON 
        ignoreProperty:  
          type: string  
          x-field-extra-annotation: "@com.fasterxml.jackson.annotation.JsonIgnore"

Answer 2

I had the same problem today, current answer as of today doesn't work anymore for me with spring (has same vendor extension) as it looks like meanwhile jackson changed the behaviour that method accessor JSONProperty (which is at getter level generated) overrides JsonIgnore from field level.

However with the following annotation on field level i could make it work:

x-field-extra-annotation: "@com.fasterxml.jackson.annotation.JsonProperty(access = JsonProperty.Access.WRITE_ONLY)"