AsyncAPI Specification
Disclaimer
Part of this content has been taken from the great work done by the folks at the Open API Initiative. Mainly because it's a great work and we want to keep as much compatibility as possible with the Open API Specification.
Version 1.0.0-rc2
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
The AsyncAPI Specification is licensed under The Apache License, Version 2.0.
Introduction
The AsyncAPI Specification is a project used to describe and document Asynchronous APIs.
The AsyncAPI Specification defines a set of files required to describe such an API.
These files can then be used to create utilities, such as documentation, integration and/or testing tools.
Table of Contents
Definitions
Message Broker
A message broker is a system in charge of message exchange. It MAY provide additional features, such as message queueing, storage or processing.
Message
A message is a piece of information a process will send to a message broker. It MUST contain headers and payload.
Topic
A topic is a routing key used by the message broker to deliver messages to the subscribed processes. Depending on the protocol used, a message MAY include the topic in its headers.
Process
A process is any kind of computer program connected to a message broker. It MUST be a producer, a consumer or both.
Producer
A producer is a process publishing messages to a message broker.
Consumer
A consumer is a process subscribed to a message broker and consumes messages from it.
Topic Templating
Topic templating refers to the usage of curly braces ({}) to mark a section of a topic as replaceable.
Specification
Format
The files describing the Asynchronous API in accordance with the AsyncAPI Specification are represented as JSON objects and conform to the JSON standards.
YAML, being a superset of JSON, can be used as well to represent a A2S (AsyncAPI Specification) file.
For example, if a field is said to have an array value, the JSON array representation will be used:
{
"field" : [...]
}
While the API is described using JSON it does not impose a JSON input/output to the API itself.
All field names in the specification are case sensitive.
The schema exposes two types of fields.
Fixed fields, which have a declared name, and Patterned fields, which declare a regex pattern for the field name.
Patterned fields can have multiple occurrences as long as each has a unique name.
In order to preserve the ability to round-trip between YAML and JSON formats, YAML version 1.2 is recommended along with some additional constraints:
- Tags MUST be limited to those allowed by the JSON Schema ruleset
- Keys used in YAML maps MUST be limited to a scalar string, as defined by the YAML Failsafe schema ruleset
File Structure
The A2S representation of the API is made of a single file.
However, parts of the definitions can be split into separate files, at the discretion of the user.
This is applicable for $ref
fields in the specification as follows from the JSON Schema definitions.
By convention, the AsyncAPI Specification (A2S) file is named asyncapi.json
or asyncapi.yaml
.
Schema
AsyncAPI Object
This is the root document object for the API specification.
It combines resource listing and API declaration together into one document.
Fixed Fields
Field Name | Type | Description |
---|
asyncapi | AsyncAPI Version String | Required. Specifies the AsyncAPI Specification version being used. It can be used by tooling Specifications and clients to interpret the version. The structure shall be major .minor .patch , where patch versions must be compatible with the existing major .minor tooling. Typically patch versions will be introduced to address errors in the documentation, and tooling should typically be compatible with the corresponding major .minor (1.0.*). Patch versions will correspond to patches of this document. |
info | Info Object | Required. Provides metadata about the API. The metadata can be used by the clients if needed. |
baseTopic | BaseTopic String | The base topic to the API. |
topics | Topics Object | Required. The available topics and messages for the API. |
components | Components Object | An element to hold various schemas for the specification. |
tags | [Tag Object] | A list of tags used by the specification with additional metadata. Each tag name in the list MUST be unique. |
externalDocs | External Documentation Object | Additional external documentation. |
This object can be extended with Specification Extensions.
AsyncAPI Version String
The version string signifies the version of the AsyncAPI Specification that the document complies to.
The format for this string must be major
.minor
.patch
. The patch
may be suffixed by a hyphen and extra alphanumeric characters.
A major
.minor
shall be used to designate the AsyncAPI Specification version, and will be considered compatible with the AsyncAPI Specification specified by that major
.minor
version.
The patch version will not be considered by tooling, making no distinction between 1.0.0
and 1.0.1
.
In subsequent versions of the AsyncAPI Specification, care will be given such that increments of the minor
version should not interfere with operations of tooling developed to a lower minor version. Thus a hypothetical 1.1.0
specification should be usable with tooling designed for 1.0.0
.
Info Object
The object provides metadata about the API.
The metadata can be used by the clients if needed.
Fixed Fields
Field Name | Type | Description |
---|
title | string | Required. The title of the application. |
version | string | Required Provides the version of the application API (not to be confused with the specification version). |
description | string | A short description of the application. CommonMark syntax can be used for rich text representation. |
termsOfService | string | A URL to the Terms of Service for the API. |
contact | Contact Object | The contact information for the exposed API. |
license | License Object | The license information for the exposed API. |
This object can be extended with Specification Extensions.
Info Object Example:
{
"title": "AsyncAPI Sample App",
"description": "This is a sample server.",
"termsOfService": "http://asyncapi.org/terms/",
"contact": {
"name": "API Support",
"url": "http://www.asyncapi.org/support",
"email": "support@asyncapi.org"
},
"license": {
"name": "Apache 2.0",
"url": "http://www.apache.org/licenses/LICENSE-2.0.html"
},
"version": "1.0.1"
}
title: AsyncAPI Sample App
description: This is a sample server.
termsOfService: http://asyncapi.org/terms/
contact:
name: API Support
url: http://www.asyncapi.org/support
email: support@asyncapi.org
license:
name: Apache 2.0
url: http://www.apache.org/licenses/LICENSE-2.0.html
version: 1.0.1
Contact Object
Contact information for the exposed API.
Fixed Fields
Field Name | Type | Description |
---|
name | string | The identifying name of the contact person/organization. |
url | string | The URL pointing to the contact information. MUST be in the format of a URL. |
email | string | The email address of the contact person/organization. MUST be in the format of an email address. |
This object can be extended with Specification Extensions.
Contact Object Example:
{
"name": "API Support",
"url": "http://www.example.com/support",
"email": "support@example.com"
}
name: API Support
url: http://www.example.com/support
email: support@example.com
License Object
License information for the exposed API.
Fixed Fields
Field Name | Type | Description |
---|
name | string | Required. The license name used for the API. |
url | string | A URL to the license used for the API. MUST be in the format of a URL. |
This object can be extended with Specification Extensions.
License Object Example:
{
"name": "Apache 2.0",
"url": "http://www.apache.org/licenses/LICENSE-2.0.html"
}
name: Apache 2.0
url: http://www.apache.org/licenses/LICENSE-2.0.html
Host String
The host (name or ip) of the target server. This MAY point to a message broker.
Host String Example:
{
"host": "myapi.example.com"
}
host: myapi.example.com
Base Topic String
The base topic to the API. You MAY use this field to avoid repeating the beginning of the topics.
Base Topic String Example:
{
"baseTopic": "hitch.accounts"
}
host: hitch.accounts
Schemes List
An array of the transfer protocol(s) the API supports. Values MUST be one (or more) of the following values:
Value | Type | Description |
---|
amqp | string | AMQP protocol. |
amqps | string | AMQP protocol over SSL/TLS. |
mqtt | string | MQTT protocol |
mqtts | string | MQTT protocol over SSL/TLS. |
ws | string | WebSockets protocol |
wss | string | WebSockets protocol over SSL/TLS. |
stomp | string | STOMP protocol. |
stomps | string | STOMP protocol over SSL/TLS. |
Schemes List Example:
{
"schemes": ["amqps", "mqtts"]
}
host:
- amqps
- mqtts
Topics Object
Holds the relative paths to the individual topic and their operations.
The topic is appended to the Base Topic
in order to construct the full one.
Patterned Fields
Field Pattern | Type | Description |
---|
^[^.]{topic} | Topic Item Object | A relative path to an individual topic. The field name MUST NOT begin with a dot. Topic templating is allowed. |
This object can be extended with Specification Extensions.
Topics Object Example
{
"accounts.1.0.event.user.signup": {
"subscribe": {
"$ref": "#/components/messages/userSignedUp"
}
}
}
accounts.1.0.event.user.signup:
subscribe:
$ref: "#/components/messages/userSignedUp"
Topic Item Object
Describes the operations available on a single topic.
Fixed Fields
Field Name | Type | Description |
---|
$ref | string | Allows for an external definition of this topic item. The referenced structure MUST be in the format of a Topic Item Object. If there are conflicts between the referenced definition and this Topic Item's definition, the behavior is undefined. |
subscribe | Message Object | A definition of the message a SUBSCRIBE operation will receive on this topic. |
publish | Message Object | A definition of the message a PUBLISH operation will receive on this topic. |
This object can be extended with Specification Extensions.
Topic Item Object Example
{
"subscribe": {
"summary": "A user signed up.",
"description": "A longer description of the message",
"payload": {
"type": "object",
"properties": {
"user": {
"$ref": "#/components/schemas/user"
},
"signup": {
"$ref": "#/components/schemas/signup"
}
}
}
}
}
subscribe:
summary: A user signed up.
description: A longer description of the message
payload:
type: object
properties:
user:
$ref: "#/components/schemas/user"
signup:
$ref: "#/components/schemas/signup"
Message Object
Describes a message received on a given topic and operation.
Fixed Fields
Field Name | Type | Description |
---|
headers | Schema Object | Definition of the message headers. It MAY or MAY NOT define the protocol headers. |
payload | Schema Object | Definition of the message payload. |
summary | string | A short summary of what the message is about. |
description | string | A verbose explanation of the message. CommonMark syntax can be used for rich text representation. |
tags | [string ] | A list of tags for API documentation control. Tags can be used for logical grouping of messages. |
externalDocs | External Documentation Object | Additional external documentation for this message. |
This object can be extended with Specification Extensions.
Message Object Example
{
"summary": "Action to sign a user up.",
"description": "A longer description",
"tags": [
{ "name" "user" },
{ "name" "signup" },
{ "name" "register" }
],
"headers": {
"type": "object",
"properties": {
"qos": {
"$ref": "#/components/schemas/MQTTQoSHeader"
},
"retainFlag": {
"$ref": "#/components/schemas/MQTTRetainHeader"
}
}
},
"payload": {
"type": "object",
"properties": {
"user": {
"$ref": "#/components/schemas/userCreate"
},
"signup": {
"$ref": "#/components/schemas/signup"
}
}
}
}
summary: Action to sign a user up.
description: A longer description
tags:
- name: user
- name: signup
- name: register
headers:
type: object
properties:
qos:
$ref: "#/components/schemas/MQTTQoSHeader"
retainFlag:
$ref: "#/components/schemas/MQTTRetainHeader"
payload:
type: object
properties:
user:
$ref: "#/components/schemas/userCreate"
signup:
$ref: "#/components/schemas/signup"
Tag Object
Allows adding meta data to a single tag.
Fixed Fields
Field Name | Type | Description |
---|
name | string | Required. The name of the tag. |
description | string | A short description for the tag. CommonMark syntax can be used for rich text representation. |
externalDocs | External Documentation Object | Additional external documentation for this tag. |
This object can be extended with Specification Extensions.
Tag Object Example
{
"name": "user",
"description": "User-related messages"
}
name: user
description: User-related messages
External Documentation Object
Allows referencing an external resource for extended documentation.
Fixed Fields
Field Name | Type | Description |
---|
description | string | A short description of the target documentation. CommonMark syntax can be used for rich text representation. |
url | string | Required. The URL for the target documentation. Value MUST be in the format of a URL. |
This object can be extended with Specification Extensions.
External Documentation Object Example
{
"description": "Find more info here",
"url": "https://example.com"
}
description: Find more info here
url: https://example.com
Reference Object
A simple object to allow referencing other components in the specification, internally and externally.
The Reference Object is defined by JSON Reference and follows the same structure, behavior and rules.
For this specification, reference resolution is done as defined by the JSON Reference specification
and not by the JSON Schema specification.
Fixed Fields
Field Name | Type | Description |
---|
$ref | string | Required. The reference string. |
This object cannot be extended with additional properties and any properties added SHALL be ignored.
Reference Object Example
{
"$ref": "#/components/schemas/Pet"
}
$ref: '#/components/schemas/Pet'
Components Object
Holds a set of reusable objects for different aspects of the AsyncAPI specification.
All objects defined within the components object will have no effect on the API unless they are explicitly referenced from properties outside the components object.
Fixed Fields
This object can be extended with Specification Extensions.
All the fixed fields declared above are objects that MUST use keys that match the regular expression: ^[a-zA-Z0-9\.\-_]+$
.
Field Name Examples:
User
User_1
User_Name
user-name
my.org.User
Components Object Example
"components": {
"schemas": {
"Category": {
"type": "object",
"properties": {
"id": {
"type": "integer",
"format": "int64"
},
"name": {
"type": "string"
}
}
},
"Tag": {
"type": "object",
"properties": {
"id": {
"type": "integer",
"format": "int64"
},
"name": {
"type": "string"
}
}
}
}
},
"messages": {
"userSignUp": {
"summary": "Action to sign a user up.",
"description": "Multiline description of what this action does.\nHere you have another line.\n",
"tags": [
{
"name": "user"
},
{
"name": "signup"
}
],
"headers": {
"type": "object",
"properties": {
"qos": {
"$ref": "#/components/schemas/MQTTQoSHeader"
},
"retainFlag": {
"$ref": "#/components/schemas/MQTTRetainHeader"
}
}
},
"payload": {
"type": "object",
"properties": {
"user": {
"$ref": "#/components/schemas/userCreate"
},
"signup": {
"$ref": "#/components/schemas/signup"
}
}
}
}
}
}
components:
schemas:
Category:
type: object
properties:
id:
type: integer
format: int64
name:
type: string
Tag:
type: object
properties:
id:
type: integer
format: int64
name:
type: string
messages:
userSignUp:
summary: Action to sign a user up.
description: |
Multiline description of what this action does.
Here you have another line.
tags:
- name: user
- name: signup
headers:
type: object
properties:
qos:
$ref: "#/components/schemas/MQTTQoSHeader"
retainFlag:
$ref: "#/components/schemas/MQTTRetainHeader"
payload:
type: object
properties:
user:
$ref: "#/components/schemas/userCreate"
signup:
$ref: "#/components/schemas/signup"
Schema Object
The Schema Object allows the definition of input and output data types.
These types can be objects, but also primitives and arrays.
This object is an extended subset of the JSON Schema Specification Wright Draft 00.
Further information about the properties can be found in JSON Schema Core and JSON Schema Validation.
Unless stated otherwise, the property definitions follow the JSON Schema specification as referenced here.
Properties
The following properties are taken directly from the JSON Schema definition and follow the same specifications:
- title
- multipleOf
- maximum
- exclusiveMaximum
- minimum
- exclusiveMinimum
- maxLength
- minLength
- pattern (This string SHOULD be a valid regular expression, according to the ECMA 262 regular expression dialect)
- maxItems
- minItems
- uniqueItems
- maxProperties
- minProperties
- required
- enum
The following properties are taken from the JSON Schema definition but their definitions were adjusted to the AsyncAPI Specification.
- type - Value MUST be a string. Multiple types via an array are not supported.
- allOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
- oneOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
- anyOf - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
- not - Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
- items - Value MUST be an object and not an array. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
items
MUST be present if the type
is array
. - properties - Property definitions MUST be a Schema Object and not a standard JSON Schema (inline or referenced).
- additionalProperties - Value can be boolean or object. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema.
- description - CommonMark syntax can be used for rich text representation.
- format - See Data Type Formats for further details. While relying on JSON Schema's defined formats, the AsyncAPI Specification offers a few additional predefined formats.
- default - The default value represents what would be assumed by the consumer of the input as the value of the schema if one is not provided. Unlike JSON Schema, the value MUST conform to the defined type for the Schema Object defined at the same level. For example, of
type
is string
, then default
can be "foo"
but cannot be 1
.
Alternatively, any time a Schema Object can be used, a Reference Object can be used in its place. This allows referencing definitions in place of defining them inline.
Additional properties defined by the JSON Schema specification that are not mentioned here are strictly unsupported.
Other than the JSON Schema subset fields, the following fields MAY be used for further schema documentation:
Fixed Fields
Field Name | Type | Description |
---|
nullable | boolean | Allows sending a null value for the defined schema. Default value is false . |
discriminator | string | Adds support for polymorphism. The discriminator is the schema property name that is used to differentiate between other schema that inherit this schema. The property name used MUST be defined at this schema and it MUST be in the required property list. When used, the value MUST be the name of this schema or any schema that inherits it. See Composition and Inheritance for more details. |
readOnly | boolean | Relevant only for Schema "properties" definitions. Declares the property as "read only". This means that it MAY be sent as part of a response but SHOULD NOT be sent as part of the request. If property is marked as readOnly being true and is in the required list, the required will take effect on the response only. A property MUST NOT be marked as both readOnly and writeOnly being true . Default value is false . |
writeOnly | boolean | Relevant only for Schema "properties" definitions. Declares the property as "write only". This means that it MAY be sent as part of a request but SHOULD NOT be sent as part of the response. If property is marked as writeOnly being true and is in the required list, the required will take effect on the request only. A property MUST NOT be marked as both readOnly and writeOnly being true . Default value is false . |
xml | XML Object | This MAY be used only on properties schemas. It has no effect on root schemas. Adds Additional metadata to describe the XML representation format of this property. |
externalDocs | External Documentation Object | Additional external documentation for this schema. |
example | Any | A free-form property to include an example of an instance for this schema. To represent examples that cannot naturally represented in JSON or YAML, a string value can be used to contain the example with escaping where necessary. |
deprecated | boolean | Specifies that a schema is deprecated and SHOULD be transitioned out of usage. Default value is false . |
This object can be extended with Specification Extensions.
Composition and Inheritance (Polymorphism)
The AsyncAPI Specification allows combining and extending model definitions using the allOf
property of JSON Schema, in effect offering model composition.
allOf
takes in an array of object definitions that are validated independently but together compose a single object.
While composition offers model extensibility, it does not imply a hierarchy between the models.
To support polymorphism, AsyncAPI Specification adds the support of the discriminator
field.
When used, the discriminator
will be the name of the property used to decide which schema definition is used to validate the structure of the model.
As such, the discriminator
field MUST be a required field.
There are are two ways to define the value of a discriminator for an inheriting instance.
- Use the schema's name.
- Override the schema's name by overriding the property with a new value. If exists, this takes precedence over the schema's name.
As such, inline schema definitions, which do not have a given id, cannot be used in polymorphism.
XML Modeling
The xml property allows extra definitions when translating the JSON definition to XML.
The XML Object contains additional information about the available options.
Schema Object Examples
Primitive Sample
{
"type": "string",
"format": "email"
}
type: string
format: email
Simple Model
{
"type": "object",
"required": [
"name"
],
"properties": {
"name": {
"type": "string"
},
"address": {
"$ref": "#/components/schemas/Address"
},
"age": {
"type": "integer",
"format": "int32",
"minimum": 0
}
}
}
type: object
required:
- name
properties:
name:
type: string
address:
$ref: '#/components/schemas/Address'
age:
type: integer
format: int32
minimum: 0
Model with Map/Dictionary Properties
For a simple string to string mapping:
{
"type": "object",
"additionalProperties": {
"type": "string"
}
}
type: object
additionalProperties:
type: string
For a string to model mapping:
{
"type": "object",
"additionalProperties": {
"$ref": "#/components/schemas/ComplexModel"
}
}
type: object
additionalProperties:
$ref: '#/components/schemas/ComplexModel'
Model with Example
{
"type": "object",
"properties": {
"id": {
"type": "integer",
"format": "int64"
},
"name": {
"type": "string"
}
},
"required": [
"name"
],
"example": {
"name": "Puma",
"id": 1
}
}
type: object
properties:
id:
type: integer
format: int64
name:
type: string
required:
- name
example:
name: Puma
id: 1
Models with Composition
{
"schemas": {
"ErrorModel": {
"type": "object",
"required": [
"message",
"code"
],
"properties": {
"message": {
"type": "string"
},
"code": {
"type": "integer",
"minimum": 100,
"maximum": 600
}
}
},
"ExtendedErrorModel": {
"allOf": [
{
"$ref": "#/components/schemas/ErrorModel"
},
{
"type": "object",
"required": [
"rootCause"
],
"properties": {
"rootCause": {
"type": "string"
}
}
}
]
}
}
}
schemas:
ErrorModel:
type: object
required:
- message
- code
properties:
message:
type: string
code:
type: integer
minimum: 100
maximum: 600
ExtendedErrorModel:
allOf:
- $ref: '#/components/schemas/ErrorModel'
- type: object
required:
- rootCause
properties:
rootCause:
type: string
Models with Polymorphism Support
{
"schemas": {
"Pet": {
"type": "object",
"discriminator": "petType",
"properties": {
"name": {
"type": "string"
},
"petType": {
"type": "string"
}
},
"required": [
"name",
"petType"
]
},
"Cat": {
"description": "A representation of a cat. Note that `Cat` will be used as the discriminator value.",
"allOf": [
{
"$ref": "#/components/schemas/Pet"
},
{
"type": "object",
"properties": {
"huntingSkill": {
"type": "string",
"description": "The measured skill for hunting",
"enum": [
"clueless",
"lazy",
"adventurous",
"aggressive"
]
}
},
"required": [
"huntingSkill"
]
}
]
},
"Dog": {
"description": "A representation of a dog. Note that `Dog` will be used as the discriminator value.",
"allOf": [
{
"$ref": "#/components/schemas/Pet"
},
{
"type": "object",
"properties": {
"packSize": {
"type": "integer",
"format": "int32",
"description": "the size of the pack the dog is from",
"minimum": 0
}
},
"required": [
"packSize"
]
}
]
}
}
}
schemas:
Pet:
type: object
discriminator: petType
properties:
name:
type: string
petType:
type: string
required:
- name
- petType
Cat:
description: A representation of a cat
allOf:
- $ref: '#/components/schemas/Pet'
- type: object
properties:
huntingSkill:
type: string
description: The measured skill for hunting
enum:
- clueless
- lazy
- adventurous
- aggressive
required:
- huntingSkill
Dog:
description: A representation of a dog
allOf:
- $ref: '#/components/schemas/Pet'
- type: object
properties:
packSize:
type: integer
format: int32
description: the size of the pack the dog is from
minimum: 0
required:
- packSize
XML Object
A metadata object that allows for more fine-tuned XML model definitions.
When using arrays, XML element names are not inferred (for singular/plural forms) and the name
property SHOULD be used to add that information.
See examples for expected behavior.
Fixed Fields
Field Name | Type | Description |
---|
name | string | Replaces the name of the element/attribute used for the described schema property. When defined within items , it will affect the name of the individual XML elements within the list. When defined alongside type being array (outside the items ), it will affect the wrapping element and only if wrapped is true . If wrapped is false , it will be ignored. |
namespace | string | The URL of the namespace definition. Value SHOULD be in the form of a URL. |
prefix | string | The prefix to be used for the name. |
attribute | boolean | Declares whether the property definition translates to an attribute instead of an element. Default value is false . |
wrapped | boolean | MAY be used only for an array definition. Signifies whether the array is wrapped (for example, <books><book/><book/></books> ) or unwrapped (<book/><book/> ). Default value is false . The definition takes effect only when defined alongside type being array (outside the items ). |
This object can be extended with Specification Extensions.
XML Object Examples
The examples of the XML object definitions are included inside a property definition of a Schema Object with a sample of the XML representation of it.
No XML Element
Basic string property:
{
"animals": {
"type": "string"
}
}
animals:
type: string
<animals>...</animals>
Basic string array property (wrapped
is false
by default):
{
"animals": {
"type": "array",
"items": {
"type": "string"
}
}
}
animals:
type: array
items:
type: string
<animals>...</animals>
<animals>...</animals>
<animals>...</animals>
XML Name Replacement
{
"animals": {
"type": "string",
"xml": {
"name": "animal"
}
}
}
animals:
type: string
xml:
name: animal
<animal>...</animal>
XML Attribute, Prefix and Namespace
In this example, a full model definition is shown.
{
"Person": {
"type": "object",
"properties": {
"id": {
"type": "integer",
"format": "int32",
"xml": {
"attribute": true
}
},
"name": {
"type": "string",
"xml": {
"namespace": "http://example.com/schema/sample",
"prefix": "sample"
}
}
}
}
}
Person:
type: object
properties:
id:
type: integer
format: int32
xml:
attribute: true
name:
type: string
xml:
namespace: http://example.com/schema/sample
prefix: sample
<Person id="123">
<sample:name xmlns:sample="http://example.com/schema/sample">example</sample:name>
</Person>
XML Arrays
Changing the element names:
{
"animals": {
"type": "array",
"items": {
"type": "string",
"xml": {
"name": "animal"
}
}
}
}
animals:
type: array
items:
type: string
xml:
name: animal
<animal>value</animal>
<animal>value</animal>
The external name
property has no effect on the XML:
{
"animals": {
"type": "array",
"items": {
"type": "string",
"xml": {
"name": "animal"
}
},
"xml": {
"name": "aliens"
}
}
}
animals:
type: array
items:
type: string
xml:
name: animal
xml:
name: aliens
<animal>value</animal>
<animal>value</animal>
Even when the array is wrapped, if no name is explicitly defined, the same name will be used both internally and externally:
{
"animals": {
"type": "array",
"items": {
"type": "string"
},
"xml": {
"wrapped": true
}
}
}
animals:
type: array
items:
type: string
xml:
wrapped: true
<animals>
<animals>value</animals>
<animals>value</animals>
</animals>
To overcome the above example, the following definition can be used:
{
"animals": {
"type": "array",
"items": {
"type": "string",
"xml": {
"name": "animal"
}
},
"xml": {
"wrapped": true
}
}
}
animals:
type: array
items:
type: string
xml:
name: animal
xml:
wrapped: true
<animals>
<animal>value</animal>
<animal>value</animal>
</animals>
Affecting both internal and external names:
{
"animals": {
"type": "array",
"items": {
"type": "string",
"xml": {
"name": "animal"
}
},
"xml": {
"name": "aliens",
"wrapped": true
}
}
}
animals:
type: array
items:
type: string
xml:
name: animal
xml:
name: aliens
wrapped: true
<aliens>
<animal>value</animal>
<animal>value</animal>
</aliens>
If we change the external element but not the internal ones:
{
"animals": {
"type": "array",
"items": {
"type": "string"
},
"xml": {
"name": "aliens",
"wrapped": true
}
}
}
animals:
type: array
items:
type: string
xml:
name: aliens
wrapped: true
<aliens>
<aliens>value</aliens>
<aliens>value</aliens>
</aliens>
Specification Extensions
While the AsyncAPI Specification tries to accommodate most use cases, additional data can be added to extend the specification at certain points.
The extensions properties are implemented as patterned fields that are always prefixed by "x-"
.
Field Pattern | Type | Description |
---|
^x- | Any | Allows extensions to the AsyncAPI Schema. The field name MUST begin with x- , for example, x-internal-id . The value can be null , a primitive, an array or an object. Can have any valid JSON format value. |
The extensions may or may not be supported by the available tooling, but those may be extended as well to add requested support (if tools are internal or open-sourced).
Data Type Formats
Primitives have an optional modifier property: format
.
The AsyncAPI specification uses several known formats to more finely define the data type being used.
However, the format
property is an open string
-valued property, and can have any value to support documentation needs.
Formats such as "email"
, "uuid"
, etc., can be used even though they are not defined by this specification.
Types that are not accompanied by a format
property follow their definition from the JSON Schema.
Tools that do not recognize a specific format
MAY default back to the type
alone, as if the format
was not specified.
The formats defined by the AsyncAPI Specification are:
Common Name | type | format | Comments |
---|
integer | integer | int32 | signed 32 bits |
long | integer | int64 | signed 64 bits |
float | number | float | |
double | number | double | |
string | string | | |
byte | string | byte | base64 encoded characters |
binary | string | binary | any sequence of octets |
boolean | boolean | | |
date | string | date | As defined by full-date - RFC3339 |
dateTime | string | date-time | As defined by date-time - RFC3339 |
password | string | password | Used to hint UIs the input needs to be obscured. |