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
:tabs-sync-option:

*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].

IMPORTANT: Only OpenAPI spec version 3.x is supported. You cannot use the old Swagger 2.0 spec.

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:

._Java-only: Rest DSL configuration with class literals_
[source,java]
----
restConfiguration().component("netty-http").bindingMode(RestBindingMode.json)
    .dataFormatProperty("prettyPrint", "true")
    .contextPath("/").port(8080)
    .apiContextPath("/api-doc")
        .apiProperty("api.title", "User API").apiProperty("api.version", "1.2.3")
        .apiProperty("cors", "true");

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. The default is
false.

|openapi.version |String |OpenApi spec version. Only spec version 3.x is supported. Is default 3.0.

|host |String |To set up 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 |To set up the base path where the REST services are available.
The path is relative (e.g., do not start with http/https) and
camel-openapi-java will calculate the absolute base path at runtime,
which will be `protocol://host:port/base.path`. If the base.path option is not set, context-path will be used.

|api.path |String |To set up the path where the API is available (eg /api-docs). The path is
relative (e.g., 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.

|api.default.consumes |String |Comma-separated list of default media types when `RestParamType.body` is used
without providing any `.consumes()` configuration. The default value is `application/json`. Note that this applies only
to the generated OpenAPI document and not to the actual REST services.

|api.default.produces |String |Comma-separated list of default media types when `outType` is used
without providing any `.produces()` configuration. The default value is `application/json`. Note that this applies only
to the generated OpenAPI document and not to the actual REST services
|===

== Adding Security Definitions in API doc

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

._Java-only: Rest DSL security definitions builder API_
[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 set up 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).

._Java-only: Rest DSL security on operations with class literals_
[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 by using `.json` or `.yaml` as suffix in the context-path
If none is specified, then the HTTP Accept header is used to detect if json or yaml can be
accepted. If either both are 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 specifying your own host, port & scheme on the REST configuration.

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