Openapi Java

Since Camel 3.1

The Rest DSL can be integrated with the camel-openapi-java module which is used for exposing the REST services and their APIs using OpenApi.

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

<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:

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.

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.

apiContextIdListing

boolean

Whether to allow listing all the CamelContext names in the JVM that has REST services. When enabled then the root path of the api-doc will list all the contexts. When disabled then no context ids is listed and the root path of the api-doc lists the current CamelContext. Is default false.

apiContextIdPattern

String

A pattern that allows to filter which CamelContext names is shown in the context listing. The pattern is using regular expression and * as wildcard. Its the same pattern matching as used by Intercept

Adding Security Definitions in API doc

Available as of Camel 3.1.0

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

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).

.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.

ContextIdListing enabled

When contextIdListing is enabled then its detecting all the running CamelContexts in the same JVM. These contexts are listed in the root path, eg /api-docs as a simple list of names in json format. To access the OpenApi documentation then the context-path must be appended with the Camel context id, such as api-docs/myCamel. The option apiContextIdPattern can be used to filter the names in this list.

JSon or Yaml

*Available as of Camel 3.1.0

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.

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.

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