public Builder setStringValue(
        com.google.devtools.cloudtrace.v2.TruncatableString.Builder builderForValue) {
      if (stringValueBuilder_ == null) {
        value_ = builderForValue.build();
        onChanged();
      } else {
        stringValueBuilder_.setMessage(builderForValue.build());
      }
      valueCase_ = 1;
      return this;
    }
<pre>
A string up to 256 bytes long.
</pre>

<code>.google.devtools.cloudtrace.v2.TruncatableString string_value = 1;</code>
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/AttributeValue.java