# Using Reactive Routes

Reactive routes propose an alternative approach to implement HTTP endpoints where you declare and chain routes. This approach became very popular in the JavaScript world, with frameworks like Express.Js or Hapi. Quarkus also offers the possibility to use reactive routes. You can implement REST API with routes only or combine them with Jakarta REST resources and servlets.

The code presented in this guide is available in this GitHub repository under the `reactive-routes-quickstart` directory

| Reactive Routes were initially introduced to provide a reactive execution model for HTTP APIs on top of the Quarkus Reactive Architecture. With the introduction of Quarkus REST (formerly RESTEasy Reactive), you can now implement reactive HTTP APIs and still use Jakarta REST annotations. Reactive Routes are still supported, especially if you want a more route-based approach, and something closer to the underlying reactive engine.

## Quarkus HTTP

Before going further, let’s have a look at the HTTP layer of Quarkus. Quarkus HTTP support is based on a non-blocking and reactive engine (Eclipse Vert.x and Netty). All the HTTP requests your application receive are handled by event loops (I/O Thread) and then are routed towards the code that manages the request. Depending on the destination, it can invoke the code managing the request on a worker thread (Servlet, Jax-RS) or use the IO Thread (reactive route). Note that because of this, a reactive route must be non-blocking or explicitly declare its blocking nature (which would result by being called on a worker thread).

See the Quarkus Reactive Architecture documentation for further details on this topic.

## Declaring reactive routes

The first way to use reactive routes is to use the `@Route` annotation. To have access to this annotation, you need to add the `quarkus-reactive-routes` extension by running this command:

CLI

    quarkus extension add quarkus-reactive-routes

Maven

    ./mvnw quarkus:add-extension -Dextensions='quarkus-reactive-routes'

Gradle

    ./gradlew addExtension --extensions='quarkus-reactive-routes'

This will add the following to your build file:

pom.xml

    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-reactive-routes</artifactId>
    </dependency>

build.gradle

    implementation("io.quarkus:quarkus-reactive-routes")

Then in a bean, you can use the `@Route` annotation as follows:

    package org.acme.reactive.routes;

    import io.quarkus.vertx.web.Route;
    import io.quarkus.vertx.web.Route.HttpMethod;
    import io.quarkus.vertx.web.RoutingExchange;
    import io.vertx.ext.web.RoutingContext;

    import jakarta.enterprise.context.ApplicationScoped;

    @ApplicationScoped (1)
    public class MyDeclarativeRoutes {

        // neither path nor regex is set - match a path derived from the method name
        @Route(methods = Route.HttpMethod.GET) (2)
        void hello(RoutingContext rc) { (3)
            rc.response().end("hello");
        }

        @Route(path = "/world")
        String helloWorld() { (4)
            return "Hello world!";
        }

        @Route(path = "/greetings", methods = Route.HttpMethod.GET)
        void greetingsQueryParam(RoutingExchange ex) { (5)
            ex.ok("hello " + ex.getParam("name").orElse("world")); (6)
        }

        @Route(path = "/greetings/:name", methods = Route.HttpMethod.GET) (7)
        void greetingsPathParam(@Param String name, RoutingExchange ex) {
            ex.ok("hello " + name);
        }
    }

1 | If there is a reactive route found on a class with no scope annotation then `@jakarta.inject.Singleton` is added automatically.
2 | The `@Route` annotation indicates that the method is a reactive route. Again, by default, the code contained in the method must not block.
3 | The method gets a `RoutingContext` as a parameter. From the `RoutingContext` you can retrieve the HTTP request (using `request()`) and write the response using `response().end(…​)`.
4 | If the annotated method does not return `void` the arguments are optional.
5 | `RoutingExchange` is a convenient wrapper of `RoutingContext` which provides some useful methods.
6 | The `RoutingExchange` is used to retrieve the request query parameter `name`.
7 | The path defines a parameter `name` which can be injected inside the method parameters using the annotation `@Param`.

More details about using the `RoutingContext` is available in the Vert.x Web documentation.

The `@Route` annotation allows you to configure:

- The `path` - for routing by path, using the Vert.x Web format

- The `regex` - for routing with regular expressions, see for more details

- The `methods` - the HTTP verbs triggering the route such as `GET`, `POST`…​

- The `type` - it can be normal (non-blocking), blocking (method dispatched on a worker thread), or failure to indicate that this route is called on failures

- The `order` - the order of the route when several routes are involved in handling the incoming request. Must be positive for regular user routes.

- The produced and consumed mime types using `produces`, and `consumes`

For instance, you can declare a blocking route as follows:

    @Route(methods = HttpMethod.POST, path = "/post", type = Route.HandlerType.BLOCKING)
    public void blocking(RoutingContext rc) {
        // ...
    }

| Alternatively, you can use `@io.smallrye.common.annotation.Blocking` and omit the `type = Route.HandlerType.BLOCKING`:
    @Route(methods = HttpMethod.POST, path = "/post")
    @Blocking
    public void blocking(RoutingContext rc) {
        // ...
    }
When `@Blocking` is used, the `type` attribute of the `@Route` is ignored.

The `@Route` annotation is repeatable and so you can declare several routes for a single method:

    @Route(path = "/first") (1)
    @Route(path = "/second")
    public void route(RoutingContext rc) {
        // ...
    }

1 | Each route can use different paths, methods…​

If no content-type header is set, then we will try to use the most acceptable content type by matching the accept header with the value of the `Route` produces attribute as defined by `io.vertx.ext.web.RoutingContext.getAcceptableContentType()`.

    @Route(path = "/person", produces = "text/html") (1)
    String person() {
        // ...
    }

1 | If the `accept` header matches `text/html`, we set the content type automatically to `text/html`.

### Executing route on a virtual thread

You can annotate a route method with `@io.smallrye.common.annotation.RunOnVirtualThread` in order to execute it on a virtual thread. However, keep in mind that not everything can run safely on virtual threads. You should read the Virtual thread support reference carefully and get acquainted with all the details.

### Handling conflicting routes

You may end up with multiple routes matching a given path. In the following example, both route matches `/accounts/me`:

    @Route(path = "/accounts/:id", methods = HttpMethod.GET)
    void getAccount(RoutingContext rc) {
      ...
    }

    @Route(path = "/accounts/me", methods = HttpMethod.GET)
    void getCurrentUserAccount(RoutingContext rc) {
      ...
    }

As a consequence, the result is not the expected one as the first route is called with the path parameter `id` set to `me`. To avoid the conflict, use the `order` attribute:

    @Route(path = "/accounts/:id", methods = HttpMethod.GET, order = 2)
    void getAccount(RoutingContext rc) {
      ...
    }

    @Route(path = "/accounts/me", methods = HttpMethod.GET, order = 1)
    void getCurrentUserAccount(RoutingContext rc) {
      ...
    }

By giving a lower order to the second route, it gets evaluated first. If the request path matches, it is invoked, otherwise the other routes are evaluated.

### `@RouteBase`

This annotation can be used to configure some defaults for reactive routes declared on a class.

    @RouteBase(path = "simple", produces = "text/plain")  (1) (2)
    public class SimpleRoutes {

        @Route(path = "ping") // the final path is /simple/ping
        void ping(RoutingContext rc) {
            rc.response().end("pong");
        }
    }

1 | The `path` value is used as a prefix for any route method declared on the class where `Route#path()` is used.
2 | The value of `produces()` is used for content-based routing for all routes where `Route#produces()` is empty.

## Reactive Route Methods

A route method must be a non-private non-static method of a CDI bean. If the annotated method returns `void` then it has to accept at least one argument - see the supported types below. If the annotated method does not return `void` then the arguments are optional.

| Methods that return `void` must end the response or the HTTP request to this route will never end. Some methods of `RoutingExchange` do it for you, others not and you must call the `end()` method of the response by yourself, please refer to its JavaDoc for more information.

A route method can accept arguments of the following types:

- `io.vertx.ext.web.RoutingContext`

- `io.quarkus.vertx.web.RoutingExchange`

- `io.vertx.core.http.HttpServerRequest`

- `io.vertx.core.http.HttpServerResponse`

- `io.vertx.mutiny.core.http.HttpServerRequest`

- `io.vertx.mutiny.core.http.HttpServerResponse`

Furthermore, it is possible to inject the `HttpServerRequest` parameters into method parameters annotated with `@io.quarkus.vertx.web.Param` using the following types:

Parameter Type | Obtained via
--- | ---
`java.lang.String` | `routingContext.request().getParam()`
`java.util.Optional<String>` | `routingContext.request().getParam()`
`java.util.List<String>` | `routingContext.request().params().getAll()`

Request Parameter Example

    @Route
    String hello(@Param Optional<String> name) {
       return "Hello " + name.orElse("world");
    }

The `HttpServerRequest` headers can be injected into method parameters annotated with `@io.quarkus.vertx.web.Header` using the following types:

Parameter Type | Obtained via
--- | ---
`java.lang.String` | `routingContext.request().getHeader()`
`java.util.Optional<String>` | `routingContext.request().getHeader()`
`java.util.List<String>` | `routingContext.request().headers().getAll()`

Request Header Example

    @Route
    String helloFromHeader(@Header("My-Header") String header) {
       return header;
    }

The request body can be injected into a method parameter annotated with `@io.quarkus.vertx.web.Body` using the following types:

Parameter Type | Obtained via
--- | ---
`java.lang.String` | `routingContext.getBodyAsString()`
`io.vertx.core.buffer.Buffer` | `routingContext.getBody()`
`io.vertx.core.json.JsonObject` | `routingContext.getBodyAsJson()`
`io.vertx.core.json.JsonArray` | `routingContext.getBodyAsJsonArray()`
any other type | `routingContext.getBodyAsJson().mapTo(MyPojo.class)`

Request Body Example

    @Route(produces = "application/json")
    Person createPerson(@Body Person person, @Param("id") Optional<String> primaryKey) {
      person.setId(primaryKey.map(Integer::valueOf).orElse(42));
      return person;
    }

A failure handler can declare a single method parameter whose type extends `Throwable`. The type of the parameter is used to match the result of `RoutingContext#failure()`.

Failure Handler Example

    @Route(type = HandlerType.FAILURE)
    void unsupported(UnsupportedOperationException e, HttpServerResponse response) {
      response.setStatusCode(501).end(e.getMessage());
    }

### Returning Unis

In a reactive route, you can return a `Uni` directly:

    @Route(path = "/hello")
    Uni<String> hello() {
        return Uni.createFrom().item("Hello world!");
    }

    @Route(path = "/person")
    Uni<Person> getPerson() {
        return Uni.createFrom().item(() -> new Person("neo", 12345));
    }

Returning `Unis` is convenient when using a reactive client:

    @Route(path = "/mail")
    Uni<Void> sendEmail() {
        return mailer.send(...);
    }

The item produced by the returned `Uni` can be:

- A string - written into the HTTP response directly.

- A `io.vertx.core.buffer.Buffer` - written into the HTTP response directly.

- An object - written into the HTTP response after having been encoded into JSON. The `content-type` header is set to `application/json` if not already set.

If the returned `Uni` produces a failure (or is `null`), an HTTP 500 response is written.

Returning a `Uni<Void>` produces a 204 response (no content).

### Returning results

You can also return a result directly:

    @Route(path = "/hello")
    String helloSync() {
        return "Hello world";
    }

Be aware, the processing must be non-blocking as reactive routes are invoked on the IO Thread. Otherwise, set the `type` attribute of the `@Route` annotation to `Route.HandlerType.BLOCKING`, or use the `@io.smallrye.common.annotation.Blocking` annotation.

The method can return:

- A string - written into the HTTP response directly.

- A `io.vertx.core.buffer.Buffer` - written into the HTTP response directly.

- An object - written into the HTTP response after having been encoded into JSON. The `content-type` header is set to `application/json` if not already set.

### Returning Multis

A reactive route can return a `Multi`. The items are written one by one, in the response. The response `Transfer-Encoding` header is set to `chunked`.

    @Route(path = "/hello")
    Multi<String> hellos() {
        return Multi.createFrom().items("hello", "world", "!");  (1)
    }

1 | Produces `helloworld!`

The method can return:

- A `Multi<String>` - the items are written one by one (one per chunk) in the response.

- A `Multi<Buffer>` - the buffers are written one by one (one per chunk) without any processing.

- A `Multi<Object>` - the items are encoded to JSON written one by one in the response.

    @Route(path = "/people")
    Multi<Person> people() {
        return Multi.createFrom().items(
                new Person("superman", 1),
                new Person("batman", 2),
                new Person("spiderman", 3));
    }

The previous snippet produces:

    {"name":"superman", "id": 1} // chunk 1
    {"name":"batman", "id": 2} // chunk 2
    {"name":"spiderman", "id": 3} // chunk 3

### Streaming JSON Array items

You can return a `Multi` to produce a JSON Array, where every item is an item from this array. The response is written item by item to the client. To do that set the `produces` attribute to `"application/json"` (or `ReactiveRoutes.APPLICATION_JSON`).

    @Route(path = "/people", produces = ReactiveRoutes.APPLICATION_JSON)
    Multi<Person> people() {
        return Multi.createFrom().items(
                new Person("superman", 1),
                new Person("batman", 2),
                new Person("spiderman", 3));
    }

The previous snippet produces:

    [
      {"name":"superman", "id": 1} // chunk 1
      ,{"name":"batman", "id": 2} // chunk 2
      ,{"name":"spiderman", "id": 3} // chunk 3
    ]

| The `produces` attribute is an array. When you pass a single value you can omit the "{" and "}". Note that `"application/json"` must be the first value in the array.

Only `Multi<String>`, `Multi<Object>` and `Multi<Void>` can be written into the JSON Array. Using a `Multi<Void>` produces an empty array. You cannot use `Multi<Buffer>`. If you need to use `Buffer`, transform the content into a JSON or String representation first.

| Deprecation of `asJsonArray` The `ReactiveRoutes.asJsonArray` has been deprecated as it is not compatible with the security layer of Quarkus.

### Event Stream and Server-Sent Event support

You can return a `Multi` to produce an event source (stream of server sent events). To enable this feature, set the `produces` attribute to `"text/event-stream"` (or `ReactiveRoutes.EVENT_STREAM`), such as in:

    @Route(path = "/people", produces = ReactiveRoutes.EVENT_STREAM)
    Multi<Person> people() {
        return Multi.createFrom().items(
                new Person("superman", 1),
                new Person("batman", 2),
                new Person("spiderman", 3));
    }

This method would produce:

    data: {"name":"superman", "id": 1}
    id: 0

    data: {"name":"batman", "id": 2}
    id: 1

    data: {"name":"spiderman", "id": 3}
    id: 2

| The `produces` attribute is an array. When you pass a single value you can omit the "{" and "}". Note that `"text/event-stream"` must be the first value in the array.

You can also implement the `io.quarkus.vertx.web.ReactiveRoutes.ServerSentEvent` interface to customize the `event` and `id` section of the server sent event:

    class PersonEvent implements ReactiveRoutes.ServerSentEvent<Person> {
        public String name;
        public int id;

        public PersonEvent(String name, int id) {
            this.name = name;
            this.id = id;
        }

        @Override
        public Person data() {
            return new Person(name, id); // Will be JSON encoded
        }

        @Override
        public long id() {
            return id;
        }

        @Override
        public String event() {
            return "person";
        }
    }

Using a `Multi<PersonEvent>` would produce:

    event: person
    data: {"name":"superman", "id": 1}
    id: 1

    event: person
    data: {"name":"batman", "id": 2}
    id: 2

    event: person
    data: {"name":"spiderman", "id": 3}
    id: 3

| Deprecation of `asEventStream` The `ReactiveRoutes.asEventStream` has been deprecated as it is not compatible with the security layer of Quarkus.

### Json Stream in NDJSON format

You can return a `Multi` to produce a newline delimited stream of JSON values. To enable this feature, set the `produces` attribute of the `@Route` annotation to `"application/x-ndjson"` (or `ReactiveRoutes.ND_JSON`):

    @Route(path = "/people", produces = ReactiveRoutes.ND_JSON)
    Multi<Person> people() {
        return ReactiveRoutes.asJsonStream(Multi.createFrom().items(
                new Person("superman", 1),
                new Person("batman", 2),
                new Person("spiderman", 3)
                ));
    }

This method would produce:

    {"name":"superman", "id": 1}
    {"name":"batman", "id": 2}
    {"name":"spiderman", "id": 3}

| The `produces` attribute is an array. When you pass a single value you can omit the "{" and "}". Note that `"application/x-ndjson"` must be the first value in the array.

You can also provide strings instead of objects, in that case the strings will be wrapped in quotes to become valid JSON values:

    @Route(path = "/people", produces = ReactiveRoutes.ND_JSON)
    Multi<Person> people() {
        return ReactiveRoutes.asJsonStream(Multi.createFrom().items(
                "superman",
                "batman",
                "spiderman"
                ));
    }

    "superman"
    "batman"
    "spiderman"

| Deprecation of `asJsonStream` The `ReactiveRoutes.asJsonStream` has been deprecated as it is not compatible with the security layer of Quarkus.

### Using Bean Validation

You can combine reactive routes and Bean Validation. First, don’t forget to add the `quarkus-hibernate-validator` extension to your project. Then, you can add constraints to your route parameter (annotated with `@Param` or `@Body`):

    @Route(produces = "application/json")
    Person createPerson(@Body @Valid Person person, @NonNull @Param("id") String primaryKey) {
      // ...
    }

If the parameters do not pass the tests, it returns an HTTP 400 response. If the request accepts JSON payload, the response follows the Problem format.

When returning an object or a `Uni`, you can also use the `@Valid` annotation:

    @Route(...)
    @Valid Uni<Person> createPerson(@Body @Valid Person person, @NonNull @Param("id") String primaryKey) {
      // ...
    }

If the item produced by the route does not pass the validation, it returns an HTTP 500 response. If the request accepts JSON payload, the response follows the Problem format.

Note that only `@Valid` is supported on the return type. The returned class can use any constraint. In the case of `Uni`, it checks the item produced asynchronously.

## Using the Vert.x Web Router

You can also register your route directly on the HTTP routing layer by registering routes directly on the `Router` object. To retrieve the `Router` instance at startup:

    public void init(@Observes Router router) {
        router.get("/my-route").handler(rc -> rc.response().end("Hello from my route"));
    }

Check the Vert.x Web documentation to know more about the route registration, options, and available handlers.

| `Router` access is provided by the `quarkus-vertx-http` extension. If you use `quarkus-rest` or `quarkus-reactive-routes`, the extension will be added automatically.

You can also receive the Mutiny variant of the Router (`io.vertx.mutiny.ext.web.Router`):

    public void init(@Observes io.vertx.mutiny.ext.web.Router router) {
        router.get("/my-route").handler(rc -> rc.response().endAndForget("Hello from my route"));
    }

## Intercepting HTTP requests

You can also register filters that would intercept incoming HTTP requests. Note that these filters are also applied for servlets, Jakarta REST resources, and reactive routes.

For example, the following code snippet registers a filter adding an HTTP header:

    package org.acme.reactive.routes;

    import io.vertx.ext.web.RoutingContext;

    public class MyFilters {

        @RouteFilter(100) (1)
        void myFilter(RoutingContext rc) {
           rc.response().putHeader("X-Header", "intercepting the request");
           rc.next(); (2)
        }
    }

1 | The `RouteFilter#value()` defines the priority used to sort the filters - filters with higher priority are called first.
2 | The filter is likely required to call the `next()` method to continue the chain.

## HTTP Compression

The body of an HTTP response is not compressed by default. You can enable the HTTP compression support by means of `quarkus.http.enable-compression=true`.

If compression support is enabled then the response body is compressed if:

- the route method is annotated with `@io.quarkus.vertx.http.Compressed`, or

- the `Content-Type` header is set and the value is a compressed media type as configured via `quarkus.http.compress-media-types`.

The response body is never compressed if:

- the route method is annotated with `@io.quarkus.vertx.http.Uncompressed`, or

- the `Content-Type` header is not set.

| By default, the following list of media types is compressed: `text/html`, `text/plain`, `text/xml`, `text/css`, `text/javascript`, `application/javascript`, `application/json`, `application/graphql+json` and `application/xhtml+xml`.

| If the client does not support HTTP compression then the response body is not compressed.

## Adding OpenAPI and Swagger UI

You can add support for OpenAPI and Swagger UI by using the `quarkus-smallrye-openapi` extension.

Add the extension by running this command:

CLI

    quarkus extension add quarkus-smallrye-openapi

Maven

    ./mvnw quarkus:add-extension -Dextensions='quarkus-smallrye-openapi'

Gradle

    ./gradlew addExtension --extensions='quarkus-smallrye-openapi'

This will add the following to your build file:

pom.xml

    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-smallrye-openapi</artifactId>
    </dependency>

build.gradle

    implementation("io.quarkus:quarkus-smallrye-openapi")

This is enough to generate a basic OpenAPI schema document from your Vert.x Routes:

    curl http://localhost:8080/q/openapi

You will see the generated OpenAPI schema document:

    ---
    openapi: 3.0.3
    info:
      title: Generated API
      version: "1.0"
    paths:
      /greetings:
        get:
          responses:
            "204":
              description: No Content
      /hello:
        get:
          responses:
            "204":
              description: No Content
      /world:
        get:
          responses:
            "200":
              description: OK
              content:
                '*/*':
                  schema:
                    type: string

Also see the OpenAPI Guide.

### Adding MicroProfile OpenAPI Annotations

You can use MicroProfile OpenAPI to better document your schema, for instance, adding header info, or specifying the return type on `void` methods might be useful:

    @OpenAPIDefinition( (1)
        info = @Info(
            title="Greeting API",
            version = "1.0.1",
            contact = @Contact(
                name = "Greeting 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"))
    )
    @ApplicationScoped
    public class MyDeclarativeRoutes {

        // neither path nor regex is set - match a path derived from the method name
        @Route(methods = Route.HttpMethod.GET)
        @APIResponse(responseCode="200",
                description="Say hello",
                content=@Content(mediaType="application/json", schema=@Schema(type=SchemaType.STRING))) (2)
        void hello(RoutingContext rc) {
            rc.response().end("hello");
        }

        @Route(path = "/world")
        String helloWorld() {
            return "Hello world!";
        }

        @Route(path = "/greetings", methods = HttpMethod.GET)
        @APIResponse(responseCode="200",
                description="Greeting",
                content=@Content(mediaType="application/json", schema=@Schema(type=SchemaType.STRING)))
        void greetings(RoutingExchange ex) {
            ex.ok("hello " + ex.getParam("name").orElse("world"));
        }
    }

1 | Header information about your API.
2 | Defining the response.

This will generate this OpenAPI schema:

    ---
    openapi: 3.0.3
    info:
      title: Greeting API
      contact:
        name: Greeting API Support
        url: http://exampleurl.com/contact
        email: techsupport@example.com
      license:
        name: Apache 2.0
        url: https://www.apache.org/licenses/LICENSE-2.0.html
      version: 1.0.1
    paths:
      /greetings:
        get:
          responses:
            "200":
              description: Greeting
              content:
                application/json:
                  schema:
                    type: string
      /hello:
        get:
          responses:
            "200":
              description: Say hello
              content:
                application/json:
                  schema:
                    type: string
      /world:
        get:
          responses:
            "200":
              description: OK
              content:
                '*/*':
                  schema:
                    type: string

### Using Swagger UI

Swagger UI is included by default when running in `dev` or `test` mode, and can optionally be added to `prod` mode. For more information, see the Swagger UI guide.

Navigate to localhost:8080/q/swagger-ui/ and observe the Swagger UI screen:

## Conclusion

This guide has introduced how you can use reactive routes to define an HTTP endpoint. It also describes the structure of the Quarkus HTTP layer and how to write filters.