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The LightStep OpenTracing Tracer implementation for Java

There is a newer version: 0.32.0

package com.lightstep.tracer.shared;

import io.opentracing.propagation.TextMapExtract;
import io.opentracing.propagation.TextMapInject;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

class TextMapPropagator implements Propagator {
    private static final Locale english = new Locale("en", "US");

    private static final String PREFIX_TRACER_STATE = "ot-tracer-";
    static final String PREFIX_BAGGAGE = "ot-baggage-";

    static final String FIELD_NAME_TRACE_ID = PREFIX_TRACER_STATE + "traceid";
    static final String FIELD_NAME_SPAN_ID = PREFIX_TRACER_STATE + "spanid";
    static final String FIELD_NAME_SAMPLED = PREFIX_TRACER_STATE + "sampled";

    public  void inject(SpanContext spanContext, final C carrier) {
        if (!(carrier instanceof TextMapInject)) {
            return;
        }

        TextMapInject textCarrier = (TextMapInject) carrier;
        textCarrier.put(FIELD_NAME_TRACE_ID, spanContext.toTraceId());
        textCarrier.put(FIELD_NAME_SPAN_ID, spanContext.toSpanId());
        textCarrier.put(FIELD_NAME_SAMPLED, "true");
        for (Map.Entry e : spanContext.baggageItems()) {
            textCarrier.put(PREFIX_BAGGAGE + e.getKey(), e.getValue());
        }
    }

    public  SpanContext extract(C carrier) {
        if (!(carrier instanceof TextMapExtract)) {
            return null;
        }

        Long traceId = null;
        Long spanId = null;
        Map baggage = new HashMap<>();

        for (Map.Entry entry : (TextMapExtract)carrier) {
            String key = entry.getKey().toLowerCase(english);

            if (FIELD_NAME_TRACE_ID.equals(key)) {
                traceId = Util.fromHexString(entry.getValue());
            }

            if (FIELD_NAME_SPAN_ID.equals(key)) {
                spanId = Util.fromHexString(entry.getValue());
            }

            if (key.startsWith(PREFIX_BAGGAGE)) {
                baggage.put(key.substring(PREFIX_BAGGAGE.length()), entry.getValue());
            }
        }

        if (traceId == null || spanId == null) {
            return null;
        }

        // Success.
        return new SpanContext(traceId, spanId, baggage);
    }
}