@java.lang.Override
    public long getSpanId() {
      return spanId_;
    }
<pre>
Identifier for the span. Must be a 64-bit integer other than 0 and
unique within a trace. For example, `2205310701640571284`.
</pre>

<code>fixed64 span_id = 1;</code>

@return The spanId.
java-trace/proto-google-cloud-trace-v1/src/main/java/com/google/devtools/cloudtrace/v1/TraceSpan.java