Interface HandlerInterceptor

All Superinterfaces:

HandlerDecorator

All Known Implementing Classes:

AuthenticatingInterceptor, ContentFilterInterceptor, DataProtectionInterceptor, DisableMetrics, ErrorReportingInterceptor, HandlerMonitor, SchedulingInterceptor, ValidatingInterceptor

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 HandlerInterceptor
extends HandlerDecorator

Intercepts individual message handling operations, enabling cross-cutting behavior around handler invocation.

A HandlerInterceptor can be used to inspect or modify messages before they are passed to a handler, monitor and log handler executions, block certain messages from being handled, or inspect and modify the return value after handling.

Interceptors are typically configured via Consumer.handlerInterceptors(), or applied programmatically using the wrap(Handler) method.

Common Use Cases:

• Validating or transforming a message before it reaches the handler
• Adding logging, tracing, or metrics for observability
• Conditionally suppressing handler invocation
• Decorating or modifying the result of a handler method

Example:

public class LoggingHandlerInterceptor implements HandlerInterceptor {
    @Override
    public Function<DeserializingMessage, Object> interceptHandling(
            Function<DeserializingMessage, Object> next, HandlerInvoker invoker) {
        return message -> {
            log.info("Before handling: {}", message.getPayload());
            Object result = next.apply(message);
            log.info("After handling: {}", result);
            return result;
        };
    }
}

See Also:

• Consumer.handlerInterceptors()
• BatchInterceptor

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	HandlerInterceptor.InterceptedHandler	Implementation of Handler that delegates to another handler and applies a HandlerInterceptor.

Nested classes/interfaces inherited from interface HandlerDecorator

HandlerDecorator.MergedDecorator

Field Summary

Fields inherited from interface HandlerDecorator

noOp

Method Summary

Modifier and Type	Method	Description
Function<DeserializingMessage, Object>	interceptHandling(Function<DeserializingMessage, Object> function, HandlerInvoker invoker)	Intercepts the message handling logic.
default Handler<DeserializingMessage>	wrap(Handler<DeserializingMessage> handler)	Wraps a Handler with this interceptor, producing an intercepted handler.

Methods inherited from interface HandlerDecorator

andThen

Method Details

interceptHandling

Function<DeserializingMessage, Object> interceptHandling(Function<DeserializingMessage, Object> function,
 HandlerInvoker invoker)

Intercepts the message handling logic.

The function parameter represents the next step in the handling chain— typically the actual message handler. The invoker provides metadata and invocation logic for the underlying handler method.

Within this method, an interceptor may:

• Modify the DeserializingMessage before passing it to the handler
• Bypass the handler entirely and return a value directly
• Wrap the result after the handler is invoked

Note: Interceptors may return a different DeserializingMessage, but it must be compatible with a handler method in the same target class. If no suitable handler is found, an exception will be thrown.

Parameters:

function - the next step in the handler chain (typically the handler itself)

invoker - the metadata and execution strategy for the actual handler method

Returns:

a decorated function that wraps handling behavior

wrap

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

Wraps a Handler with this interceptor, producing an intercepted handler.

Specified by:

wrap in interface HandlerDecorator

Parameters:

handler - the original handler to wrap

Returns:

an intercepted handler that applies this interceptor to all handled messages