components/camel-openapi-java/src/main/docs/openapi-java.adoc

= Openapi Java Component
:doctitle: Openapi Java
:shortname: openapi-java
:artifactid: camel-openapi-java
:description: Rest-dsl support for using openapi doc
:since: 3.1
:supportlevel: Stable
//Manually maintained attributes
:camel-spring-boot-name: openapi-java

*Since Camel {since}*

The  Rest DSL can be integrated with
the `camel-openapi-java` module which is used for exposing the REST
services and their APIs using https://www.openapis.org/[OpenApi].

Maven users will need to add the following dependency to
their `pom.xml` for this component:

[source,xml]
----
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-openapi-java</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>
----

The camel-openapi-java module can be used from
the REST components (without the need for servlet)

== Using OpenApi in rest-dsl

You can enable the OpenApi api from the rest-dsl by configuring the
`apiContextPath` dsl as shown below:

[source,java]
----
public class UserRouteBuilder extends RouteBuilder {
    @Override
    public void configure() throws Exception {
        // configure we want to use servlet as the component for the rest DSL
        // and we enable json binding mode
        restConfiguration().component("netty-http").bindingMode(RestBindingMode.json)
            // and output using pretty print
            .dataFormatProperty("prettyPrint", "true")
            // setup context path and port number that netty will use
            .contextPath("/").port(8080)
            // add OpenApi api-doc out of the box
            .apiContextPath("/api-doc")
                .apiProperty("api.title", "User API").apiProperty("api.version", "1.2.3")
                // and enable CORS
                .apiProperty("cors", "true");

        // this user REST service is json only
        rest("/user").description("User rest service")
            .consumes("application/json").produces("application/json")
            .get("/{id}").description("Find user by id").outType(User.class)
                .param().name("id").type(path).description("The id of the user to get").dataType("int").endParam()
                .to("bean:userService?method=getUser(${header.id})")
            .put().description("Updates or create a user").type(User.class)
                .param().name("body").type(body).description("The user to update or create").endParam()
                .to("bean:userService?method=updateUser")
            .get("/findAll").description("Find all users").outType(User[].class)
                .to("bean:userService?method=listUsers");
    }
}
----
 

== Options

The OpenApi module can be configured using the following options. To
configure using a servlet you use the init-param as shown above. When
configuring directly in the rest-dsl, you use the appropriate method,
such as `enableCORS`, `host,contextPath`, dsl. The options
with `api.xxx` is configured using `apiProperty` dsl.

[width="100%",cols="10%,10%,80%",options="header",]
|===
|Option |Type |Description

|cors |Boolean |Whether to enable CORS. Notice this only enables CORS for the api
browser, and not the actual access to the REST services. Is default
false.

|openapi.version |String |OpenApi spec version. Is default 3.0.

|host |String |To setup the hostname. If not configured camel-openapi-java will
calculate the name as localhost based.

|schemes |String |The protocol schemes to use. Multiple values can be
separated by comma such as "http,https". The default value is "http".

|base.path |String |*Required*: To setup the base path where the REST services is available.
The path is relative (eg do not start with http/https) and
camel-openapi-java will calculate the absolute base path at runtime,
which will be `protocol://host:port/context-path/base.path`

|api.path |String |To setup the path where the API is available (eg /api-docs). The path is
relative (eg do not start with http/https) and camel-openapi-java will
calculate the absolute base path at runtime, which will be `protocol://host:port/context-path/api.path`
So using relative paths is much easier. See above for an example.

|api.version |String |The version of the api. Is default 0.0.0.

|api.title |String |The title of the application.

|api.description |String |A short description of the application.

|api.termsOfService |String |A URL to the Terms of Service of the API.

|api.contact.name |String |Name of person or organization to contact

|api.contact.email |String |An email to be used for API-related correspondence.

|api.contact.url |String |A URL to a website for more contact information.

|api.license.name |String |The license name used for the API.

|api.license.url |String |A URL to the license used for the API.
|===

== Adding Security Definitions in API doc

The Rest DSL now supports declaring OpenApi `securityDefinitions` in the generated API document.
For example as shown below:

[source,java]
----
rest("/user").tag("dude").description("User rest service")
    // setup security definitions
    .securityDefinitions()
        .oauth2("petstore_auth").authorizationUrl("http://petstore.swagger.io/oauth/dialog").end()
        .apiKey("api_key").withHeader("myHeader").end()
    .end()
    .consumes("application/json").produces("application/json")
----

Here we have setup two security definitions

- OAuth2 - with implicit authorization with the provided url
- Api Key - using an api key that comes from HTTP header named _myHeader_

Then you need to specify on the rest operations which security to use by referring to
their key (petstore_auth or api_key).

[source,java]
----
.get("/{id}/{date}").description("Find user by id and date").outType(User.class)
    .security("api_key")

...

.put().description("Updates or create a user").type(User.class)
    .security("petstore_auth", "write:pets,read:pets")
----

Here the get operation is using the Api Key security and the put operation
is using OAuth security with permitted scopes of read and write pets.

== JSon or Yaml

The camel-openapi-java module supports both JSon and Yaml out of the
box. You can specify in the request url what you want returned by using
/openapi.json or /openapi.yaml for either one. If none is specified then
the HTTP Accept header is used to detect if json or yaml can be
accepted. If either both is accepted or none was set as accepted then
json is returned as the default format.

== useXForwardHeaders and API URL resolution

The OpenApi specification allows you to specify the host, port & path that is serving the API. In OpenApi V2 this is done
via the `host` field and in OpenAPI V3 it is part of the `servers` field.

By default, the value for these fields is determined by `X-Forwarded` headers, `X-Forwarded-Host` & `X-Forwarded-Proto`.

This can be overridden by disabling the lookup of `X-Forwarded` headers and by specifying your own host, port & scheme on the REST configuration.

[source,java]
----
restConfiguration().component("netty-http")
    .useXForwardHeaders(false)
    .apiProperty("schemes", "https");
    .host("localhost")
    .port(8080);
----

== Examples

In the Apache Camel distribution we ship the `camel-example-openapi-cdi`
and `camel-example-spring-boot-rest-openapi-simple` which demonstrates
using this OpenApi component.

include::spring-boot:partial$starter.adoc[]