REST Swagger Component

Available from Camel 2.19

The rest-swagger configures rest producers from Swagger (Open API) specification document and delegates to a component implementing the RestProducerFactory interface. Currently known working components are:

• HTTP component
• HTTP4 component
• Netty4 component
• Restlet component
• Jetty component
• Undertow component

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

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-rest-swagger</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

rest-swagger:[specificationPath#]operationId

Where operationId is the ID of the operation in the Swagger specification, and specificationPath is the path to the specification.
If the `specificationPath` is not specified it defaults to swagger.json. The lookup mechanism uses Camel's ResourceHelper to load the resource, which means that you can use CLASSPATH resources (classpath:my-specification.json), files (file:/some/path.json), the web (http://api.example.com/swagger.json) or reference a bean (ref:nameOfBean) or use a method of a bean (bean:nameOfBean.methodName) to get the specification resource, failing that Swagger's own resource loading support.

This component does not act as a HTTP client, it delegates that to another component mentioned above. The lookup mechanism searches for a single component that implements the RestProducerFactory interface and uses that. If the CLASSPATH contains more than one, then the property componentName should be set to indicate which component to delegate to.

Most of the configuration is taken from the Swagger specification but the option exists to override those by specifying them on the component or on the endpoint. Typically you would just need to override the host or basePath if those differ from the specification.

NOTE: The host parameter should contain the absolute URI containing scheme, hostname and port number, for instance https://api.example.com.

With componentName you specify what component is used to perform the requests, this named component needs to be present in the Camel context and implement the required RestProducerFactory interface - as do the components listed at the top.

If you do not specify the componentName at either component or endpoint level, CLASSPATH is searched for a suitable delegate. There should be only one component present on the CLASSPATH that implements the RestProducerFactory interface for this to work.

Example: PetStore

Checkout the example in the camel-example-rest-swagger project in the examples directory.

For example if you wanted to use the PetStore provided REST API simply reference the specification URI and desired operation id from the Swagger specification or download the specification and store it as swagger.json (in the root) of CLASSPATH that way it will be automaticaly used. Let’s use the Undertow component to perform all the requests and Camels excelent support for Spring Boot.

Here are our dependencies defined in Maven POM file:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-undertow-starter</artifactId>
</dependency>

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-rest-swagger-starter</artifactId>
</dependency>

Start by defining the Undertow component and the RestSwaggerComponent:

@Bean
public Component petstore(CamelContext camelContext, UndertowComponent undertow) {
    RestSwaggerComponent petstore = new RestSwaggerComponent(camelContext);
    petstore.setSpecificationUri("http://petstore.swagger.io/v2/swagger.json");
    petstore.setDelegate(undertow);

    return petstore;
}

NOTE: Support in Camel for Spring Boot will auto create the UndertowComponent Spring bean, and you can configure it using application.properties (or application.yml) using prefix camel.component.undertow.. We are defining the petstore component here in order to have a named component in the Camel context that we can use to interact with the PetStore REST API, if this is the only rest-swagger component used we might configure it in the same manner (using application.properties).

Now in our application we can simply use the ProducerTemplate to invoke PetStore REST methods:

@Autowired
ProducerTemplate template;

String getPetJsonById(int petId) {
    return template.requestBodyAndHeaders("petstore:getPetById", null, "petId", petId);
}