Package org.apache.juneau.rest.server.tracing

Interface TraceContextExtractor

public interface TraceContextExtractor

SPI for recognizing a non-HTTP trace-context carrier inside a resolved @RestOp invocation.

RestOpInvoker resolves every operation argument (path/query/body parameters, parsed request beans, etc.) before it opens a TracerHook span. A registered TraceContextExtractor bean gets a look at those resolved arguments — not just the raw RestRequest — so it can recognize a domain-specific carrier (for example a parsed JSON-RPC/MCP request's nested params._meta object) and hand back a TraceContextCarrier plus a TraceOperation before the span is created. Neither this interface nor its default implementation depends on MCP, JSON-RPC, or OpenTelemetry.

Extraction only happens when a non-no-op TracerHook is active; a resource with no registered TracerHook bean never resolves a TraceContextExtractor either, preserving the existing zero-allocation no-op fast path.

See Also:

• TraceContextCarrier
• TraceOperation
• TracerHook
• Observability — Micrometer + OpenTelemetry

Since:

10.0.0

Method Summary

Modifier and Type	Method	Description
Optional<TraceContextCarrier>	extract(RestRequest request, Object[] resolvedArguments)	Attempts to recognize a non-HTTP trace-context carrier among the resolved operation arguments.
default TraceOperation	operation(RestRequest request, Object[] resolvedArguments)	Derives the TraceOperation a bridge should name/attribute its span with.

Method Details

extract

Optional<TraceContextCarrier> extract(RestRequest request,
 Object[] resolvedArguments)

Attempts to recognize a non-HTTP trace-context carrier among the resolved operation arguments.

Parameters:

request - The in-flight RestRequest. Never null.

resolvedArguments - The fully-resolved @RestOp handler arguments, in declaration order. Never null; may be empty.

Returns:

The recognized TraceContextCarrier, or Optional.empty() if this extractor found nothing to extract from the resolved arguments (the bridge then falls back to HTTP headers only). Never null.

operation

default TraceOperation operation(RestRequest request,
 Object[] resolvedArguments)

Derives the TraceOperation a bridge should name/attribute its span with.

The default implementation returns TraceOperation.DEFAULT — an extractor that overrides only extract(org.apache.juneau.rest.server.RestRequest, java.lang.Object[]) still satisfies TracerHook.startSpan's three-argument overload, and the bridge keeps its own HTTP-derived span name/attributes.

Parameters:

request - The in-flight RestRequest. Never null.

resolvedArguments - The fully-resolved @RestOp handler arguments, in declaration order. Never null; may be empty.

Returns:

The derived TraceOperation. Never null.