Add google format version (#9)

Extracted out of #6

Author: sbernauer

pom.xml

@@ -37,6 +37,7 @@
 
     <cleanthat.version>2.17</cleanthat.version>
     <error-prone.version>2.24.1</error-prone.version>
+    <google-java-format.version>1.19.2</google-java-format.version>
 
     <maven-clean-plugin.version>3.3.2</maven-clean-plugin.version>
     <maven-compiler-plugin.version>3.12.1</maven-compiler-plugin.version>

src/main/java/tech/stackable/hadoop/StackableGroupMapper.java

@@ -21,12 +21,8 @@
 
 public class StackableGroupMapper implements GroupMappingServiceProvider {
 
-  private static final Logger LOG = LoggerFactory.getLogger(StackableGroupMapper.class);
-
   public static final String OPA_MAPPING_URL_PROP = "hadoop.security.group.mapping.opa.policy.url";
-  // response base field: see https://www.openpolicyagent.org/docs/latest/rest-api/#response-message
-  private static final String OPA_RESULT_FIELD = "result";
-
+  private static final Logger LOG = LoggerFactory.getLogger(StackableGroupMapper.class);
   private final HttpClient httpClient = HttpClient.newHttpClient();
   private final ObjectMapper json;
   private URI opaUri;
@@ -59,12 +55,10 @@ public StackableGroupMapper() {
             .setSerializationInclusion(JsonInclude.Include.NON_NULL);
   }
 
-  private static class OpaQueryResult {
-    public List<String> result;
-  }
-
   /**
-   * Returns list of groups for a user.
+   * Returns list of groups for a user. Internally Hadoop will pass the short name to this function,
+   * but this prevents us from effectively separating users with the same names but with different
+   * kerberos principals.
    *
    * @param user get groups for this user
    * @return list of groups for a given user
@@ -139,4 +133,8 @@ public void cacheGroupsAdd(List<String> groups) {
         "ignoring cacheGroupsAdd for groups [{}]: caching should be provided by the policy provider",
         groups);
   }
+
+  private static class OpaQueryResult {
+    public List<String> result;
+  }
 }