OpenAPI Extensions Reference

Apitomy Codegen uses OpenAPI specification extensions (vendor extensions) to customize code generation directly from your API contract.

All extensions use the x-codegen prefix.

Extension Summary

Extension	Placement	Description
x-codegen	Document root	Global codegen configuration block
x-codegen-contextRoot	paths object	Base path prefix for all generated JAX-RS resources
x-codegen-package	Schema definition	Custom Java package for a specific bean class
x-codegen-annotations	Schema definition	Extra Java annotations on a specific bean class
x-codegen-extendsClass	Schema definition	Superclass for a generated bean class
x-codegen-type	Schema definition	Override the Java type for a schema (map types)
x-codegen-inline	Schema definition	Inline a schema instead of generating a separate class
x-codegen-async	Operation	Mark an operation's return type as asynchronous
x-codegen-returnType	Media type (in response)	Override the return type for a specific operation
x-codegen-formatPattern	Schema property (date-time)	Custom date-time format pattern

---

Global Configuration

x-codegen

A root-level configuration block that controls global code generation behavior. This extension is placed at the top level of the OpenAPI document (alongside openapi, info, paths, etc.).

Sub-properties:

Property	Type	Description
bean-annotations	Array	Annotations to add to all generated bean classes
contextRoot	String	Global context root path (alternative to x-codegen-contextRoot on paths)
suppress-date-time-formatting	Boolean	Disable @JsonFormat on date-time fields

x-codegen.bean-annotations

Adds Java annotations to all generated bean classes. Each array element can be either:

• A string — the fully qualified annotation (e.g. "lombok.ToString")
• An object with annotation and optional excludeEnums properties

JSONYAML

{
  "x-codegen": {
    "bean-annotations": [
      "jakarta.enterprise.context.ApplicationScoped",
      {
        "annotation": "lombok.ToString(callSuper=true, includeFieldNames=true)",
        "excludeEnums": true
      }
    ]
  }
}

x-codegen:
  bean-annotations:
    - jakarta.enterprise.context.ApplicationScoped
    - annotation: "lombok.ToString(callSuper=true, includeFieldNames=true)"
      excludeEnums: true

Generated bean class:

@JsonInclude(JsonInclude.Include.NON_NULL)
@Generated("jsonschema2pojo")
@jakarta.enterprise.context.ApplicationScoped
@lombok.ToString(callSuper=true, includeFieldNames=true)
public class FooBean {
    // ...
}

When excludeEnums is true, the annotation is not added to generated Java enum classes.

x-codegen.contextRoot

Defines a global base path prefix that is prepended to all generated JAX-RS resource @Path annotations. This is an alternative to using x-codegen-contextRoot on the paths object.

{
  "x-codegen": {
    "contextRoot": "/apis/studio/v1"
  }
}

Generated resource:

@Path("/apis/studio/v1/users")
public interface UsersResource {
    // ...
}

x-codegen.suppress-date-time-formatting

By default, Apitomy Codegen generates @JsonFormat annotations on properties of type string with format date-time:

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss'Z'", timezone = "UTC")
@JsonProperty("shipDate")
private Date shipDate;

Set suppress-date-time-formatting to true to remove these @JsonFormat annotations:

{
  "x-codegen": {
    "suppress-date-time-formatting": true
  }
}

---

Path-Level Extensions

x-codegen-contextRoot

Placed on the paths object, this extension defines a base path prefix that is prepended to all generated JAX-RS resource @Path annotations.

JSONYAML

{
  "paths": {
    "/widgets": {
      "get": { "..." : "..." }
    },
    "x-codegen-contextRoot": "/api/v3"
  }
}

paths:
  /widgets:
    get: ...
  x-codegen-contextRoot: /api/v3

Without context root:

@Path("/widgets")
public interface WidgetsResource { }

With context root /api/v3:

@Path("/api/v3/widgets")
public interface WidgetsResource { }

Tip

Use this to align generated code with your application's deployment path without modifying every path in the OpenAPI spec.

---

Schema-Level Extensions

x-codegen-package

Overrides the Java package for a specific generated bean class. By default, beans are placed in the beans sub-package of your configured javaPackage.

{
  "components": {
    "schemas": {
      "AuditEvent": {
        "type": "object",
        "x-codegen-package": "com.example.api.audit",
        "properties": {
          "action": { "type": "string" }
        }
      }
    }
  }
}

Effect: The AuditEvent class is generated in com.example.api.audit instead of the default com.example.api.beans.

---

x-codegen-annotations

Adds Java annotations to a specific bean class. This is the per-schema equivalent of the global x-codegen.bean-annotations.

The value is an array of fully qualified annotation class names:

{
  "components": {
    "schemas": {
      "MyBean": {
        "type": "object",
        "x-codegen-annotations": [
          "io.quarkus.runtime.annotations.RegisterForReflection"
        ],
        "properties": {
          "name": { "type": "string" }
        }
      }
    }
  }
}

Generated bean:

@JsonInclude(JsonInclude.Include.NON_NULL)
@Generated("jsonschema2pojo")
@io.quarkus.runtime.annotations.RegisterForReflection
public class MyBean {
    // ...
}

Note

Per-schema annotations are applied in addition to any global x-codegen.bean-annotations.

---

x-codegen-extendsClass

Makes a generated bean class extend a specified superclass.

{
  "components": {
    "schemas": {
      "RuleViolationError": {
        "type": "object",
        "x-codegen-extendsClass": "com.example.api.beans.Error",
        "properties": {
          "causes": {
            "type": "array",
            "items": { "$ref": "#/components/schemas/RuleViolationCause" }
          }
        }
      }
    }
  }
}

Generated bean:

public class RuleViolationError extends Error {
    // Only properties specific to RuleViolationError
}

Can be combined with x-codegen-annotations:

{
  "MySchema": {
    "type": "object",
    "x-codegen-extendsClass": "org.example.api.beans.AbstractSchema",
    "x-codegen-annotations": ["lombok.AllArgsConstructor", "lombok.Builder"],
    "properties": { "..." : "..." }
  }
}

---

x-codegen-type

Overrides the Java type mapping for a schema. This is primarily used for map types where you want to use a specific Java map implementation.

Supported type values:

Extension Value	Java Type
map	java.util.Map<String, Object>

{
  "components": {
    "schemas": {
      "Metadata": {
        "type": "object",
        "x-codegen-type": "map",
        "additionalProperties": true
      }
    }
  }
}

---

x-codegen-inline

Marks a schema definition as "inline", meaning it will not generate a separate bean class. Instead, its type will be inlined wherever it is referenced.

{
  "components": {
    "schemas": {
      "SimpleId": {
        "type": "string",
        "x-codegen-inline": true
      }
    }
  }
}

When SimpleId is referenced elsewhere (e.g. as a property type or parameter type), it will be replaced with String directly rather than generating a SimpleId class.

This is useful for trivial wrapper types that don't warrant their own class.

---

Operation-Level Extensions

x-codegen-async

Marks an individual operation's return type as asynchronous by wrapping it in CompletionStage<>. This is the per-operation equivalent of the global reactive setting.

Place this extension on the operation object:

JSONYAML

{
  "paths": {
    "/items": {
      "get": {
        "operationId": "listItems",
        "x-codegen-async": true,
        "responses": {
          "200": {
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": { "$ref": "#/components/schemas/Item" }
                }
              }
            }
          }
        }
      }
    }
  }
}

paths:
  /items:
    get:
      operationId: listItems
      x-codegen-async: true
      responses:
        "200":
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/Item"

Generated interface method:

@GET
@Produces("application/json")
CompletionStage<List<Item>> listItems();

Tip

Use x-codegen-async when you want async behavior on specific operations rather than enabling reactive globally.

---

x-codegen-returnType

Overrides the Java return type of a generated JAX-RS interface method. Place this extension on the media type object inside a response.

{
  "paths": {
    "/widgets/{widgetId}": {
      "get": {
        "operationId": "getWidget",
        "responses": {
          "200": {
            "content": {
              "application/json": {
                "schema": { "$ref": "#/components/schemas/Widget" },
                "x-codegen-returnType": "jakarta.ws.rs.core.Response"
              }
            }
          }
        }
      }
    }
  }
}

Generated interface method:

@GET
@Path("/{widgetId}")
@Produces("application/json")
Response getWidget(@PathParam("widgetId") String widgetId);

This is useful when you need full control over the HTTP response (status codes, headers, etc.) for specific operations.

---

Property-Level Extensions

x-codegen-formatPattern

Overrides the default date-time format pattern for a specific date-time property.

By default, date-time properties are annotated with:

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss'Z'", timezone = "UTC")

Use x-codegen-formatPattern to change the pattern:

{
  "components": {
    "schemas": {
      "Event": {
        "type": "object",
        "properties": {
          "scheduledAt": {
            "type": "string",
            "format": "date-time",
            "x-codegen-formatPattern": "yyyy-MM-dd HH:mm:ss.SSSZ"
          }
        }
      }
    }
  }
}

Generated property:

@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm:ss.SSSZ", timezone = "UTC")
@JsonProperty("scheduledAt")
private Date scheduledAt;

Note

To suppress date-time formatting entirely (remove all @JsonFormat annotations), use the global x-codegen.suppress-date-time-formatting setting instead.