openapi-json-schema-generator

Generate JSON schema from an OpenAPI schema

Only supports OpenAPI v3.0 Schema Objects on Component Object.

Features

Generate for different JSON Schema Drafts

• JSON Schema Draft 4
• JSON Schema Draft 6
  • Changed semantic of exclusiveMinimum and exclusiveMaximum
• JSON Schema Draft 7
  • Support for readOnly and writeOnly
  • Support for contentEncoding (Used for format: byte)
• JSON Schema Draft 2019-09
  • Use #/$defs instead of #/definitions for definitions
  • Support for deprecated

Support for OpenAPIs nullable extension

# ...
components:
  schemas:
    NullableString:
      type: string
      nullable: true
    NullableEnum:
      type: string
      enum: ["a", "b", "c"]
      nullable: true

Results in:

{
  "$schema" : "https://json-schema.org/draft/2019-09/schema",
  "$defs" : {
    "NullableString" : {
      "type" : [ "string", "null" ]
    },
    "NullableEnum": {
      "type" : [ "string", "null" ],
      "enum": [ "a", "b", "c", null ]
    }
  }
}

Support for OpenAPIs example extension

# ...
components:
  schemas:
    String:
      type: string
      example: "abc"

Results in:

{
  "$schema" : "https://json-schema.org/draft/2019-09/schema",
  "$defs" : {
    "StringRef" : {
      "type" : [ "string" ],
      "examples": [ "abc" ]
    }
  }
}

References

References to other schemas are redirected:

# ...
components:
  schemas:
    StringRef:
      $ref: '#/components/schemas/String'
    String:
      type: string

Results in:

{
  "$schema" : "https://json-schema.org/draft/2019-09/schema",
  "$defs" : {
    "StringRef" : {
      "$ref" : "#/$defs/String"
    },
    "String" : {
      "type" : [ "string" ]
    }
  }
}

Main Schema

A main schema can be selected: openapi-json-schema-generator INPUT MySchema

So the JSON schema can be directly used to validate a single schema.

# ...
components:
  schemas:
    MySchema:
      type: string

Results in:

{
  "$schema" : "https://json-schema.org/draft/2019-09/schema",
  "$ref" : "#/$defs/MySchema",
  "$defs" : {
    "MySchema" : {
      "type" : [ "string" ]
    }
  }
}

Usage

Usage: openapi-json-schema-generator [-hV] [--exclude-read-only]
                                     [--exclude-write-only]
                                     [--json-schema-version=<jsonSchemaDraft>]
                                     INPUT [MAIN_SCHEMA]
Generate JSON schema from Open API specification
      INPUT                  Reference to OpenAPI specification in JSON or YAML
                               format
      [MAIN_SCHEMA]          Name of schema ('MySchema') or reference to schema
                               ('#/components/schemas/MySchema') to use as
                               top-level schema. Allows to use output to
                               directly validate this schema.
      --exclude-read-only    Exclude read only properties.
      --exclude-write-only   Exclude write only properties.
  -h, --help                 Show this help message and exit.
      --json-schema-version=<jsonSchemaDraft>
                             Use this JSON Schema Draft for output. Choices: 4,
                               6, 7, 2019-09
                               Default: 2019-09
  -V, --version              Print version information and exit.

License

This code is under the Apache Licence v2.