@Path("/expensive-resource")
public class ExpensiveResource {

    public static final String EXPENSIVE_RESOURCE_CACHE_NAME = "expensiveResourceCache";

    private int invocations;

    @Inject
    ClientRequestService clientRequestService;

 @GET
    @Path("/{keyElement1}/{keyElement2}/{keyElement3}")
    @CacheResult(cacheName = EXPENSIVE_RESOURCE_CACHE_NAME, lockTimeout = 5000)
    public ExpensiveResponse getExpensiveResponse(@PathParam("keyElement1") @CacheKey String keyElement1,
            @PathParam("keyElement2") @CacheKey String keyElement2, @PathParam("keyElement3") @CacheKey String keyElement3,
            @QueryParam("foo") String foo) {
        invocations++;
        clientRequestService.setData("request data");
        ExpensiveResponse response = new ExpensiveResponse();
        response.setResult(keyElement1 + " " + keyElement2 + " " + keyElement3 + " too!");
        return response;
    }

@RequestScoped
public class ClientRequestService {
    String data;

    public String data() {
        return data;
    }

    public ClientRequestService setData(String data) {
        this.data = data;
        return this;
    }
}

@Provider
public class ClientRequestFilter implements jakarta.ws.rs.client.ClientRequestFilter {

    ClientRequestService requestService;

    @Inject
    public ClientRequestFilter(ClientRequestService requestService) {
        this.requestService = requestService;
    }

    @Override
    public void filter(ClientRequestContext requestContext) {
        if (requestService != null) {
            requestContext.getHeaders().add("extra", requestService.data());
        }
    }
}