Using OpenAPI and Swagger UI
This guide explains how your Quarkus application can expose its API description through an OpenAPI specification and how you can test it via a user-friendly UI named Swagger UI.
Prerequisites
To complete this guide, you need:
-
Roughly 15 minutes
-
An IDE
-
JDK 11+ installed with
JAVA_HOME
configured appropriately -
Apache Maven 3.8.8
-
Optionally the Quarkus CLI if you want to use it
-
Optionally Mandrel or GraalVM installed and configured appropriately if you want to build a native executable (or Docker if you use a native container build)
Architecture
In this guide, we create a straightforward REST application to demonstrate how fast you can expose your API specification and benefit from a user interface to test it.
Solution
We recommend that you follow the instructions in the next sections and create the application step by step. However, you can skip right to the completed example.
Clone the Git repository: git clone https://github.com/quarkusio/quarkus-quickstarts.git
, or download an archive.
The solution is located in the openapi-swaggerui-quickstart
directory.
Creating the Maven project
First, we need a new project. Create a new project with the following command:
Expose a REST Resource
We will create a Fruit
bean and a FruitResource
REST resource
(feel free to take a look to the Writing JSON REST services guide if your want more details on how to build a REST API with Quarkus).
package org.acme.openapi.swaggerui;
public class Fruit {
public String name;
public String description;
public Fruit() {
}
public Fruit(String name, String description) {
this.name = name;
this.description = description;
}
}
package org.acme.openapi.swaggerui;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.POST;
import jakarta.ws.rs.DELETE;
import jakarta.ws.rs.Path;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Set;
@Path("/fruits")
public class FruitResource {
private Set<Fruit> fruits = Collections.newSetFromMap(Collections.synchronizedMap(new LinkedHashMap<>()));
public FruitResource() {
fruits.add(new Fruit("Apple", "Winter fruit"));
fruits.add(new Fruit("Pineapple", "Tropical fruit"));
}
@GET
public Set<Fruit> list() {
return fruits;
}
@POST
public Set<Fruit> add(Fruit fruit) {
fruits.add(fruit);
return fruits;
}
@DELETE
public Set<Fruit> delete(Fruit fruit) {
fruits.removeIf(existingFruit -> existingFruit.name.contentEquals(fruit.name));
return fruits;
}
}
You can also create a test:
package org.acme.openapi.swaggerui;
import io.quarkus.test.junit.QuarkusTest;
import org.junit.jupiter.api.Test;
import jakarta.ws.rs.core.MediaType;
import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.Matchers.containsInAnyOrder;
@QuarkusTest
public class FruitResourceTest {
@Test
public void testList() {
given()
.when().get("/fruits")
.then()
.statusCode(200)
.body("$.size()", is(2),
"name", containsInAnyOrder("Apple", "Pineapple"),
"description", containsInAnyOrder("Winter fruit", "Tropical fruit"));
}
@Test
public void testAdd() {
given()
.body("{\"name\": \"Pear\", \"description\": \"Winter fruit\"}")
.header("Content-Type", MediaType.APPLICATION_JSON)
.when()
.post("/fruits")
.then()
.statusCode(200)
.body("$.size()", is(3),
"name", containsInAnyOrder("Apple", "Pineapple", "Pear"),
"description", containsInAnyOrder("Winter fruit", "Tropical fruit", "Winter fruit"));
given()
.body("{\"name\": \"Pear\", \"description\": \"Winter fruit\"}")
.header("Content-Type", MediaType.APPLICATION_JSON)
.when()
.delete("/fruits")
.then()
.statusCode(200)
.body("$.size()", is(2),
"name", containsInAnyOrder("Apple", "Pineapple"),
"description", containsInAnyOrder("Winter fruit", "Tropical fruit"));
}
}
Expose OpenAPI Specifications
Quarkus provides the Smallrye OpenAPI extension compliant with the MicroProfile OpenAPI specification in order to generate your API OpenAPI v3 specification.
You just need to add the openapi
extension to your Quarkus application:
quarkus extension add 'quarkus-smallrye-openapi'
./mvnw quarkus:add-extension -Dextensions='quarkus-smallrye-openapi'
./gradlew addExtension --extensions='quarkus-smallrye-openapi'
This will add the following to your build file:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-smallrye-openapi</artifactId>
</dependency>
implementation("io.quarkus:quarkus-smallrye-openapi")
Now, we are ready to run our application:
quarkus dev
./mvnw quarkus:dev
./gradlew --console=plain quarkusDev
Once your application is started, you can make a request to the default /q/openapi
endpoint:
$ curl http://localhost:8080/q/openapi
openapi: 3.0.3
info:
title: Generated API
version: "1.0"
paths:
/fruits:
get:
responses:
200:
description: OK
content:
application/json: {}
post:
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/Fruit'
responses:
200:
description: OK
content:
application/json: {}
delete:
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/Fruit'
responses:
200:
description: OK
content:
application/json: {}
components:
schemas:
Fruit:
properties:
description:
type: string
name:
type: string
If you do not like the default endpoint location
|
You can request the OpenAPI in JSON format using the
|
Hit CTRL+C
to stop the application.
Providing Application Level OpenAPI Annotations
There are some MicroProfile OpenAPI annotations which describe global API information, such as the following:
-
API Title
-
API Description
-
Version
-
Contact Information
-
License
All of this information (and more) can be included in your Java code by using appropriate OpenAPI annotations
on a Jakarta REST Application
class. Because a Jakarta REST Application
class is not required in Quarkus, you will
likely have to create one. It can simply be an empty class that extends jakarta.ws.rs.core.Application
. This
empty class can then be annotated with various OpenAPI annotations such as @OpenAPIDefinition
. For example:
@OpenAPIDefinition(
tags = {
@Tag(name="widget", description="Widget operations."),
@Tag(name="gasket", description="Operations related to gaskets")
},
info = @Info(
title="Example API",
version = "1.0.1",
contact = @Contact(
name = "Example API Support",
url = "http://exampleurl.com/contact",
email = "techsupport@example.com"),
license = @License(
name = "Apache 2.0",
url = "https://www.apache.org/licenses/LICENSE-2.0.html"))
)
public class ExampleApiApplication extends Application {
}
Another option, that is a feature provided by SmallRye and not part of the specification, is to use configuration to add this global API information.
This way, you do not need to have a Jakarta REST Application
class, and you can name the API differently per environment.
For example, add the following to your application.properties
:
quarkus.smallrye-openapi.info-title=Example API
%dev.quarkus.smallrye-openapi.info-title=Example API (development)
%test.quarkus.smallrye-openapi.info-title=Example API (test)
quarkus.smallrye-openapi.info-version=1.0.1
quarkus.smallrye-openapi.info-description=Just an example service
quarkus.smallrye-openapi.info-terms-of-service=Your terms here
quarkus.smallrye-openapi.info-contact-email=techsupport@example.com
quarkus.smallrye-openapi.info-contact-name=Example API Support
quarkus.smallrye-openapi.info-contact-url=http://exampleurl.com/contact
quarkus.smallrye-openapi.info-license-name=Apache 2.0
quarkus.smallrye-openapi.info-license-url=https://www.apache.org/licenses/LICENSE-2.0.html
This will give you similar information as the @OpenAPIDefinition
example above.
Loading OpenAPI Schema From Static Files
Instead of dynamically creating OpenAPI schemas from annotation scanning, Quarkus also supports serving static OpenAPI documents.
The static file to serve must be a valid document conforming to the OpenAPI specification.
An OpenAPI document that conforms to the OpenAPI Specification is itself a valid JSON object, that can be represented in yaml
or json
formats.
To see this in action, we’ll put OpenAPI documentation under META-INF/openapi.yaml
for our /fruits
endpoints.
Quarkus also supports alternative OpenAPI document paths if you prefer.
openapi: 3.0.1
info:
title: Static OpenAPI document of fruits resource
description: Fruit resources Open API documentation
version: "1.0"
servers:
- url: http://localhost:8080/q/openapi
description: Optional dev mode server description
paths:
/fruits:
get:
responses:
200:
description: OK - fruits list
content:
application/json: {}
post:
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/Fruit'
responses:
200:
description: new fruit resource created
content:
application/json: {}
delete:
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/Fruit'
responses:
200:
description: OK - fruit resource deleted
content:
application/json: {}
components:
schemas:
Fruit:
properties:
description:
type: string
name:
type: string
By default, a request to /q/openapi
will serve the combined OpenAPI document from the static file and the model generated from application endpoints code.
We can however change this to only serve the static OpenAPI document by adding mp.openapi.scan.disable=true
configuration into application.properties
.
Now, a request to /q/openapi
endpoint will serve the static OpenAPI document instead of the generated one.
About OpenAPI document paths
Quarkus supports various paths to store your OpenAPI document under. We recommend you place it under
Live reload of static OpenAPI document is supported during development. A modification to your OpenAPI document will be picked up on fly by Quarkus. |
Changing the OpenAPI version
By default, when the document is generated, the OpenAPI version used will be 3.0.3
. If you use a static file as mentioned above, the version in the file
will be used. You can also define the version in SmallRye using the following configuration:
mp.openapi.extensions.smallrye.openapi=3.0.2
This might be useful if your API goes through a Gateway that needs a certain version.
Auto-generation of Operation Id
The Operation Id can be set using the @Operation
annotation, and is in many cases useful when using a tool to generate a client stub from the schema.
The Operation Id is typically used for the method name in the client stub. In SmallRye, you can auto-generate this Operation Id by using the following configuration:
mp.openapi.extensions.smallrye.operationIdStrategy=METHOD
Now you do not need to use the @Operation
annotation. While generating the document, the method name will be used for the Operation Id.
Property value | Description |
---|---|
|
Use the method name. |
|
Use the class name (without the package) plus the method. |
|
Use the class name plus the method name. |
Use Swagger UI for development
When building APIs, developers want to test them quickly. Swagger UI is a great tool permitting to visualize and interact with your APIs. The UI is automatically generated from your OpenAPI specification.
The Quarkus smallrye-openapi
extension comes with a swagger-ui
extension embedding a properly configured Swagger UI page.
By default, Swagger UI is only available when Quarkus is started in dev or test mode. If you want to make it available in production too, you can include the following configuration in your
This is a build time property, it cannot be changed at runtime after your application is built. |
By default, Swagger UI is accessible at /q/swagger-ui
.
You can update the /swagger-ui
sub path by setting the quarkus.swagger-ui.path
property in your application.properties
:
quarkus.swagger-ui.path=my-custom-path
The value |
Now, we are ready to run our application:
./mvnw compile quarkus:dev
You can check the Swagger UI path in your application’s log:
00:00:00,000 INFO [io.qua.swa.run.SwaggerUiServletExtension] Swagger UI available at /q/swagger-ui
Once your application is started, you can go to http://localhost:8080/q/swagger-ui and play with your API.
You can visualize your API’s operations and schemas.
You can also interact with your API in order to quickly test it.
Hit CTRL+C
to stop the application.
Styling
You can style the swagger ui by supplying your own logo and css.
Logo
To supply your own logo, you need to place a file called logo.png
in src/main/resources/META-INF/branding
.
This will set the logo for all UIs (not just swagger ui), so in this case also GraphQL-UI and Health-UI (if included).
If you only want to apply this logo to swagger-ui (and not globally to all UIs) call the file smallrye-open-api-ui.png
rather than logo.png
.
CSS
To supply your own css that override/enhance style in the html, you need to place a file called style.css
in src/main/resources/META-INF/branding
.
This will add that css to all UIs (not just swagger ui), so in this case also GraphQL-UI and Health-UI (if included).
If you only want to apply this style to swagger-ui (and not globally to all UIs) call the file smallrye-open-api-ui.css
rather than style.css
.
For more information on styling, read this blog entry: https://quarkus.io/blog/stylish-api/
Cross Origin Resource Sharing
If you plan to consume this application from a Single Page Application running on a different domain, you will need to configure CORS (Cross-Origin Resource Sharing). Please read the HTTP CORS documentation for more details.
Configuration Reference
OpenAPI
Configuration property fixed at build time - All other configuration properties are overridable at runtime
Type |
Default |
|
---|---|---|
The path at which to register the OpenAPI Servlet. Environment variable: |
string |
|
If set, the generated OpenAPI schema documents will be stored here on build. Both openapi.json and openapi.yaml will be stored here if this is set. Environment variable: |
path |
|
Do not run the filter only at startup, but every time the document is requested (dynamic). Environment variable: |
boolean |
|
Do not include the provided static openapi document (eg. META-INF/openapi.yaml) Environment variable: |
boolean |
|
A list of local directories that should be scanned for yaml and/or json files to be included in the static model. Example: Environment variable: |
list of path |
|
Environment variable: |
|
|
Add a Security Scheme name to the generated OpenAPI document Environment variable: |
string |
|
Add a description to the Security Scheme Environment variable: |
string |
|
This will automatically add the security requirement to all methods/classes that has a Environment variable: |
boolean |
|
This will automatically add tags to operations based on the Java class name. Environment variable: |
boolean |
|
Setting it to Environment variable: |
boolean |
|
This will automatically add security based on the security extension included (if any). Environment variable: |
boolean |
|
Add a scheme value to the Basic HTTP Security Scheme Environment variable: |
string |
|
Add a scheme value to the JWT Security Scheme Environment variable: |
string |
|
Add a bearer format the JWT Security Scheme Environment variable: |
string |
|
Add a scheme value to the OAuth2 opaque token Security Scheme Environment variable: |
string |
|
Add a scheme value to OAuth2 opaque token Security Scheme Environment variable: |
string |
|
Add a openIdConnectUrl value to the OIDC Security Scheme Environment variable: |
string |
|
Add a implicit flow refreshUrl value to the OAuth2 Security Scheme Environment variable: |
string |
|
Add an implicit flow authorizationUrl value to the OAuth2 Security Scheme Environment variable: |
string |
|
Add an implicit flow tokenUrl value to the OAuth2 Security Scheme Environment variable: |
string |
|
Override the openapi version in the Schema document Environment variable: |
string |
|
Set the title in Info tag in the Schema document Environment variable: |
string |
|
Set the version in Info tag in the Schema document Environment variable: |
string |
|
Set the description in Info tag in the Schema document Environment variable: |
string |
|
Set the terms of the service in Info tag in the Schema document Environment variable: |
string |
|
Set the contact email in Info tag in the Schema document Environment variable: |
string |
|
Set the contact name in Info tag in the Schema document Environment variable: |
string |
|
Set the contact url in Info tag in the Schema document Environment variable: |
string |
|
Set the license name in Info tag in the Schema document Environment variable: |
string |
|
Set the license url in Info tag in the Schema document Environment variable: |
string |
|
Set the strategy to automatically create an operation Id Environment variable: |
|
|
Enable the openapi endpoint. By default it’s enabled. Environment variable: |
boolean |
|
Specify the list of global servers that provide connectivity information Environment variable: |
list of string |
|
Add one or more extensions to the security scheme Environment variable: |
|
Swagger UI
Configuration property fixed at build time - All other configuration properties are overridable at runtime
Type |
Default |
|
---|---|---|
The path where Swagger UI is available.
The value Environment variable: |
string |
|
If this should be included every time. By default, this is only included when the application is running in dev mode. Environment variable: |
boolean |
|
If urls option is used, this will be the name of the default selection. Environment variable: |
string |
|
The html title for the page. Environment variable: |
string |
|
Swagger UI theme to be used. Environment variable: |
|
|
A footer for the html page. Nothing by default. Environment variable: |
string |
|
If set to true, enables deep linking for tags and operations. Environment variable: |
boolean |
|
Controls the display of operationId in operations list. The default is false. Environment variable: |
boolean |
|
The default expansion depth for models (set to -1 completely hide the models). Environment variable: |
int |
|
The default expansion depth for the model on the model-example section. Environment variable: |
int |
|
Controls how the model is shown when the API is first rendered. Environment variable: |
string |
|
Controls the display of the request duration (in milliseconds) for "Try it out" requests. Environment variable: |
boolean |
|
Controls the default expansion setting for the operations and tags. Environment variable: |
|
|
If set, enables filtering. The top bar will show an edit box that you can use to filter the tagged operations that are shown. Can be Boolean to enable or disable, or a string, in which case filtering will be enabled using that string as the filter expression. Filtering is case-sensitive matching the filter expression anywhere inside the tag. Environment variable: |
string |
|
If set, limits the number of tagged operations displayed to at most this many. The default is to show all operations. Environment variable: |
int |
|
Apply a sort to the operation list of each API. It can be 'alpha' (sort by paths alphanumerically), 'method' (sort by HTTP method) or a function (see Array.prototype.sort() to know how sort function works). Default is the order returned by the server unchanged. Environment variable: |
string |
|
Controls the display of vendor extension (x-) fields and values for Operations, Parameters, and Schema. Environment variable: |
boolean |
|
Controls the display of extensions (pattern, maxLength, minLength, maximum, minimum) fields and values for Parameters. Environment variable: |
boolean |
|
Apply a sort to the tag list of each API. It can be 'alpha' (sort by paths alphanumerically) or a function (see Array.prototype.sort() to learn how to write a sort function). Two tag name strings are passed to the sorter for each pass. Default is the order determined by Swagger UI. Environment variable: |
string |
|
Provides a mechanism to be notified when Swagger UI has finished rendering a newly provided definition. Environment variable: |
string |
|
Set to Environment variable: |
string |
|
OAuth redirect URL. Environment variable: |
string |
|
MUST be a function. Function to intercept remote definition, "Try it out", and OAuth 2.0 requests. Accepts one argument requestInterceptor(request) and must return the modified request, or a Promise that resolves to the modified request. Environment variable: |
string |
|
If set, MUST be an array of command line options available to the curl command. This can be set on the mutated request in the requestInterceptor function. Environment variable: |
list of string |
|
MUST be a function. Function to intercept remote definition, "Try it out", and OAuth 2.0 responses. Accepts one argument responseInterceptor(response) and must return the modified response, or a Promise that resolves to the modified response. Environment variable: |
string |
|
If set to true, uses the mutated request returned from a requestInterceptor to produce the curl command in the UI, otherwise the request before the requestInterceptor was applied is used. Environment variable: |
boolean |
|
List of HTTP methods that have the "Try it out" feature enabled. An empty array disables "Try it out" for all operations. This does not filter the operations from the display. Environment variable: |
list of HttpMethod |
|
By default, Swagger UI attempts to validate specs against swagger.io’s online validator. You can use this parameter to set a different validator URL, for example for locally deployed validators (Validator Badge). Setting it to either none, 127.0.0.1 or localhost will disable validation. Environment variable: |
string |
|
If set to true, enables passing credentials, as defined in the Fetch standard, in CORS requests that are sent by the browser. Environment variable: |
boolean |
|
Function to set default values to each property in model. Accepts one argument modelPropertyMacro(property), property is immutable Environment variable: |
string |
|
Function to set default value to parameters. Accepts two arguments parameterMacro(operation, parameter). Operation and parameter are objects passed for context, both remain immutable Environment variable: |
string |
|
If set to true, it persists authorization data and it would not be lost on browser close/refresh Environment variable: |
boolean |
|
The name of a component available via the plugin system to use as the top-level layout for Swagger UI. Environment variable: |
string |
|
A list of plugin functions to use in Swagger UI. Environment variable: |
list of string |
|
A list of presets to use in Swagger UI. Environment variable: |
list of string |
|
OAuth default clientId - Used in the initOAuth method. Environment variable: |
string |
|
OAuth default clientSecret - Used in the initOAuth method. Environment variable: |
string |
|
OAuth1 Realm query parameter added to authorizationUrl and tokenUrl - Used in the initOAuth method. Environment variable: |
string |
|
OAuth application name, displayed in authorization popup - Used in the initOAuth method. Environment variable: |
string |
|
OAuth scope separator for passing scopes - Used in the initOAuth method. Environment variable: |
string |
|
OAuth Scopes, separated using the oauthScopeSeparator - Used in the initOAuth method. Environment variable: |
string |
|
OAuth additional query parameters added to authorizationUrl and tokenUrl - Used in the initOAuth method. Environment variable: |
string |
|
OAuth only activated for the accessCode flow. During the authorization_code request to the tokenUrl, pass the Client Password using the HTTP Basic Authentication scheme - Used in the initOAuth method. Environment variable: |
boolean |
|
OAuth only applies to authorization code flows. Proof Key for Code Exchange brings enhanced security for OAuth public clients - Used in the initOAuth method. Environment variable: |
boolean |
|
Pre-authorize Basic Auth, programmatically set DefinitionKey for a Basic authorization scheme - Used in the preauthorizeBasic method. Environment variable: |
string |
|
Pre-authorize Basic Auth, programmatically set Username for a Basic authorization scheme - Used in the preauthorizeBasic method. Environment variable: |
string |
|
Pre-authorize Basic Auth, programmatically set Password for a Basic authorization scheme - Used in the preauthorizeBasic method. Environment variable: |
string |
|
Pre-authorize ApiKey Auth, programmatically set DefinitionKey for an API key or Bearer authorization scheme - Used in the preauthorizeApiKey method. Environment variable: |
string |
|
Pre-authorize ApiKey Auth, programmatically set ApiKeyValue for an API key or Bearer authorization scheme - Used in the preauthorizeApiKey method. Environment variable: |
string |
|
If set to true, this allows the user to modify and test different query parameters in the API request Environment variable: |
boolean |
|
If Swagger UI is included, it should be enabled/disabled. By default, Swagger UI is enabled if it is included (see Environment variable: |
boolean |
|
The urls that will be included as options. By default, the OpenAPI path will be used. Here you can override that and supply multiple urls that will appear in the TopBar plugin. Environment variable: |
|