NG Interceptors

A RestCallInterceptor observes or modifies a call at three points. All methods have no-op defaults, so implement only what you need.

public interface RestCallInterceptor {
    default void onInit(RestRequest req) throws Exception {}
    default void onConnect(RestRequest req, RestResponse res) throws Exception {}
    default void onClose(RestRequest req, RestResponse res) throws Exception {}
}

Hook	Runs	Typical use
onInit	After the request is built, before it is sent.	Add headers (signing, correlation ids).
onConnect	After the response status and headers arrive, before the body is read.	Metrics, auth refresh checks.
onClose	In run()'s finally block, before the debug logger; res can be null if the call failed before a response.	Cleanup, timing.

RestCallInterceptor stamp = new RestCallInterceptor() {
    @Override public void onInit(RestRequest req) {
        req.header("X-Start", String.valueOf(System.nanoTime()));
    }
};

RestClient client = RestClient.builder().interceptors(stamp).build();

Registration and order

Interceptors can be registered on the client builder, on a @Remote interface, on a @RemoteOp method, or on a single request with RestRequest.interceptors(...). They run in that order (builder, interface, method/request). The built-in request-id interceptor always runs first; it adds a UUIDv7 X-Request-Id header unless you disable it with sendRequestId(false) or set your own with requestId(...).

See Declarative Remote-Proxy Features for the annotation forms, and Logging and Debugging for the debug pipeline.