Fix hexadecimal flag parsing in Jaeger propagator (#8975)

Co-authored-by: Jack Berg <34418638+jack-berg@users.noreply.github.com>

Author: kamikazeayoup

extensions/trace-propagators/src/main/java/io/opentelemetry/extension/trace/propagation/JaegerPropagator.java

@@ -402,7 +402,7 @@ private static SpanContext buildSpanContext(String traceId, String spanId, Strin
     try {
       String otelTraceId = StringUtils.padLeft(traceId, MAX_TRACE_ID_LENGTH);
       String otelSpanId = StringUtils.padLeft(spanId, MAX_SPAN_ID_LENGTH);
-      int flagsInt = Integer.parseInt(flags);
+      int flagsInt = Integer.parseInt(flags, 16);
       return SpanContext.createFromRemoteParent(
           otelTraceId,
           otelSpanId,

extensions/trace-propagators/src/test/java/io/opentelemetry/extension/trace/propagation/JaegerPropagatorTest.java

@@ -366,6 +366,29 @@ void extract_SampledContext() {
                 TRACE_ID, SPAN_ID, TraceFlags.getSampled(), TraceState.getDefault()));
   }
 
+  @ParameterizedTest
+  @MethodSource
+  void extract_HexadecimalFlags(byte flags, String encodedFlags, TraceFlags expectedTraceFlags) {
+    Map<String, String> carrier = new LinkedHashMap<>();
+    JaegerSpanContext context =
+        new JaegerSpanContext(
+            TRACE_ID_HI, TRACE_ID_LOW, SPAN_ID_LONG, DEPRECATED_PARENT_SPAN_LONG, flags);
+    carrier.put(PROPAGATION_HEADER, TextMapCodec.contextAsString(context));
+
+    assertThat(carrier.get(PROPAGATION_HEADER)).endsWith(":" + encodedFlags);
+    assertThat(getSpanContext(jaegerPropagator.extract(Context.root(), carrier, getter)))
+        .isEqualTo(
+            SpanContext.createFromRemoteParent(
+                TRACE_ID, SPAN_ID, expectedTraceFlags, TraceState.getDefault()));
+  }
+
+  static Stream<Arguments> extract_HexadecimalFlags() {
+    return Stream.of(
+        Arguments.argumentSet("sampled debug firehose", (byte) 0x0b, "b", TraceFlags.getSampled()),
+        Arguments.argumentSet("unsampled hex", (byte) 0x0a, "a", TraceFlags.getDefault()),
+        Arguments.argumentSet("two-digit hex", (byte) 0xff, "ff", TraceFlags.getSampled()));
+  }
+
   @Test
   void extract_NotSampledContext() {
     Map<String, String> carrier = new LinkedHashMap<>();