public static TableName ofNullable(String dbTableName, String defaultDb, String tableMetaRef) throws SemanticException {
    if (dbTableName == null) {
      return new TableName(null, null, null);
    } else {
      try {
        return fromString(dbTableName, SessionState.get().getCurrentCatalog(), defaultDb, tableMetaRef);
      } catch (IllegalArgumentException e) {
        throw new SemanticException(e);
      }
    }
  }
Accepts qualified name which is in the form of table, dbname.tablename or catalog.dbname.tablename and returns a
{@link TableName}. All parts can be null.

@param dbTableName
@param defaultDb
@return a {@link TableName}
@throws SemanticException
@deprecated use {@link #of(String)} or {@link #fromString(String, String, String)}
ql/src/java/org/apache/hadoop/hive/ql/parse/HiveTableName.java