Java 9 and higher builds were broken by the maven-flatten-plugin because of this profile in the pom:

    <profile>
      <id>java9</id>
      <activation>
        <jdk>[9,)</jdk>
      </activation>
      <dependencies>
        <dependency>
          <groupId>javax.annotation</groupId>
          <artifactId>javax.annotation-api</artifactId>
          <version>1.3.2</version>
        </dependency>
      </dependencies>
    </profile>

This breakage does not seem to have been picked up by the (samples) tests, while it did break the samples once those were updated to the latest version of the Spanner client. These kinds of errors should be detected by the tests in the client library.

See also GoogleCloudPlatform/java-docs-samples#3182