Interface HandlerDecorator

All Known Subinterfaces:

HandlerInterceptor

All Known Implementing Classes:

AuthenticatingInterceptor, ContentFilterInterceptor, DataProtectionInterceptor, DisableMetrics, DocumentHandlerDecorator, ErrorReportingInterceptor, HandlerDecorator.MergedDecorator, HandlerMonitor, SchedulingInterceptor, ValidatingInterceptor, WebsocketHandlerDecorator

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface HandlerDecorator

Functional interface for decorating Handler instances that process DeserializingMessage objects.

A HandlerDecorator is used to wrap a handler with additional behavior. This provides a flexible mechanism for implementing cross-cutting concerns such as authorization, metrics, context propagation, or logging.

Unlike HandlerInterceptor, which focuses on message-level interception, a HandlerDecorator wraps the entire handler object and can be applied at a higher level—for example, before handler resolution occurs.

Composition

Decorators can be chained using andThen(HandlerDecorator), allowing multiple layers of behavior to be composed in a defined order.

Example:

public class MetricsDecorator implements HandlerDecorator {
    @Override
    public Handler<DeserializingMessage> wrap(Handler<DeserializingMessage> handler) {
        return new Handler<>() {
            @Override
            public Optional<HandlerInvoker> getInvoker(DeserializingMessage message) {
                return handler.getInvoker(message);
            }

            @Override
            public Class<?> getTargetClass() {
                return handler.getTargetClass();
            }

            @Override
            public Object invoke(BiFunction<Object, Object, Object> combiner) {
                long start = System.nanoTime();
                Object result = handler.getInvoker(message).orElseThrow().invoke(combiner);
                metrics.recordLatency(System.nanoTime() - start);
                return result;
            }
        };
    }
}

See Also:

• HandlerInterceptor

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	HandlerDecorator.MergedDecorator	A composite decorator that merges two decorators into one.

Field Summary

Fields

Modifier and Type	Field	Description
static final HandlerDecorator	noOp	A no-op decorator that returns the original handler unmodified.

Method Summary

Modifier and Type	Method	Description
default HandlerDecorator	andThen(HandlerDecorator next)	Chains this decorator with another, producing a composite decorator.
Handler<DeserializingMessage>	wrap(Handler<DeserializingMessage> handler)	Wraps the given handler with additional behavior.

Field Details

noOp

static final HandlerDecorator noOp

A no-op decorator that returns the original handler unmodified.

Method Details

wrap

Handler<DeserializingMessage> wrap(Handler<DeserializingMessage> handler)

Wraps the given handler with additional behavior.

Parameters:

handler - the original handler to be wrapped

Returns:

a decorated handler

andThen

default HandlerDecorator andThen(HandlerDecorator next)

Chains this decorator with another, producing a composite decorator.

The next decorator is applied first, followed by this decorator.

Parameters:

next - the decorator to apply before this one

Returns:

a combined HandlerDecorator