Chapter 273. REST Component

rest://method:path[:uriTemplate]?[options]

The REST component supports 4 options which are listed below.

The REST endpoint is configured using URI syntax:

rest:method:path:uriTemplate

with the following path and query parameters:

The following components support rest consumer (Rest DSL):

The following components support rest producer:

The path and uriTemplate option is defined using a REST syntax where you define the REST context path using support for parameters. 

TIP:If no uriTemplate is configured then path option works the same way. It does not matter if you configure only path or if you configure both options. Though configuring both a path and uriTemplate is a more common practice with REST.

The following is a Camel route using a a path only

from("rest:get:hello")
  .transform().constant("Bye World");

And the following route uses a parameter which is mapped to a Camel header with the key "me".

from("rest:get:hello/{me}")
  .transform().simple("Bye ${header.me}");

The following examples have configured a base path as "hello" and then have two REST services configured using uriTemplates.

from("rest:get:hello:/{me}")
  .transform().simple("Hi ${header.me}");

from("rest:get:hello:/french/{me}")
  .transform().simple("Bonjour ${header.me}");

You can use the rest component to call REST services like any other Camel component.

For example to call a REST service on using hello/{me} you can do

from("direct:start")
  .to("rest:get:hello/{me}");

And then the dynamic value {me} is mapped to Camel message with the same name. So to call this REST service you can send an empty message body and a header as shown:

template.sendBodyAndHeader("direct:start", null, "me", "Donald Duck");

The Rest producer needs to know the hostname and port of the REST service, which you can configure using the host option as shown:

from("direct:start")
  .to("rest:get:hello/{me}?host=myserver:8080/foo");

Instead of using the host option, you can configure the host on the restConfiguration as shown:

restConfiguration().host("myserver:8080/foo");

from("direct:start")
  .to("rest:get:hello/{me}");

You can use the producerComponent to select which Camel component to use as the HTTP client, for example to use http4 you can do:

restConfiguration().host("myserver:8080/foo").producerComponent("http4");

from("direct:start")
  .to("rest:get:hello/{me}");

The REST producer supports binding using JSon or XML like the rest-dsl does.

For example to use jetty with json binding mode turned on you can configure this in the rest configuration:

restConfiguration().component("jetty").host("localhost").port(8080).bindingMode(RestBindingMode.json);

from("direct:start")
  .to("rest:post:user");

Then when calling the REST service using rest producer it will automatic bind any POJOs to json before calling the REST service:

  UserPojo user = new UserPojo();
  user.setId(123);
  user.setName("Donald Duck");

  template.sendBody("direct:start", user);

In the example above we send a POJO instance UserPojo as the message body. And because we have turned on JSon binding in the rest configuration, then the POJO will be marshalled from POJO to JSon before calling the REST service.

However if you want to also perform binding for the response message (eg what the REST service send back as response) you would need to configure the outType option to specify what is the classname of the POJO to unmarshal from JSon to POJO.

For example if the REST service returns a JSon payload that binds to com.foo.MyResponsePojo you can configure this as shown:

  restConfiguration().component("jetty").host("localhost").port(8080).bindingMode(RestBindingMode.json);

  from("direct:start")
    .to("rest:post:user?outType=com.foo.MyResponsePojo");

See Rest DSL which offers more examples and how you can use the Rest DSL to define those in a nicer RESTful way.

There is a camel-example-servlet-rest-tomcat example in the Apache Camel distribution, that demonstrates how to use the Rest DSL with SERVLET as transport that can be deployed on Apache Tomcat, or similar web containers.