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MicroProfile Rest Client adds the capability to invoke remote services by defining a Java interface with Jakarta REST (JAX-RS) annotations that resembles a server-side resource class.

Helidon will automatically create a proxy class for the interface and map local proxy calls to remote REST calls.

For more information, see Rest Client For MicroProfile Specification.

To enable MicroProfile Rest Client either add a dependency on the helidon-microprofile bundle or add the following dependency to your project’s pom.xml (see Managing Dependencies).

<dependency>
    <groupId>io.helidon.microprofile.rest-client</groupId>
    <artifactId>helidon-microprofile-rest-client</artifactId>
</dependency>

Creating a New Client Using a Builder

SomeResource greetResource = RestClientBuilder.newBuilder()
                                 .baseUri(URI.create("http://localhost:8080/greet"))
                                 .build(GreetRestClient.class);
greetResource.getDefaultMessage();

SomeResource greetResource = RestClientBuilder.newBuilder()
                                 .baseUri(URI.create("http://localhost:8080"))
                                 .register(GreetClientRequestFilter.class)
                                 .register(GreetClientExceptionMapper.class)
                                 .build(GreetRestClient.class);
greetResource.getDefaultMessage();

Creating a New Client Using CDI

@Path("/greet")
@RegisterRestClient(baseUri="http://localhost:8080")
public interface GreetRestClient {
    // ...
}

@Path("/greet")
@RegisterRestClient(baseUri="http://localhost:8080")
@RegisterProvider(GreetClientRequestFilter.class)
@RegisterProvider(GreetClientExceptionMapper.class)
public interface GreetRestClient {
    // ...
}

public class MyBean {
    @Inject
    @RestClient
    GreetRestClient client;

    void myMethod() {
        client.getMessage("Helidon");
    }
}

Configuration is only available for CDI managed client instances, it is not supported for client created programmatically using RestClientBuilder.

Most of the configuration properties mentioned below have to be prepended with the fully qualified classname of the client interface to be configured.

It is possible to avoid fully qualified classname by using @RegisterRestClient(configKey="clientAlias"), the prefix $restClient is used below to indicate an alias or a class name.

Configuration options

To be able to run and test this example, use the Helidon MP examples/quickstarts. Add a dependency on the Helidon Rest Client implementation and create the following client interface:

@Path("/greet")
interface GreetRestClient {

     @GET
     JsonObject getDefaultMessage();

     @Path("/{name}")
     @GET
     JsonObject getMessage(@PathParam("name") String name);

}

Then create a runnable method as described in Creating new client, but with baseUri http://localhost:8080/greet and the above interface.

By calling GreetRestClient.getDefaultMessage() you reach the endpoint of Helidon quickstart.

• Helidon MicroProfile RestClient JavaDoc

• MicroProfile RestClient Specification

• MicroProfile RestClient on GitHub