[HDFS-14172] Avoid NPE when SectionName#fromString returns null

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Hadoop Flags: Reviewed
• Assignee: Xiang Li
• Reporter: Xiang Li
• Created: 25/Dec/18 03:24
• Updated: 08/Feb/19 13:42
• Resolved: 08/Feb/19 12:53

Description

In FSImageFormatProtobuf.SectionName#fromString(), as follows:

public static SectionName fromString(String name) {
  for (SectionName n : values) {
    if (n.name.equals(name))
      return n;
  }
  return null;
}

When the code meets an unknown section from the fsimage, the function will return null. Callers always operates the return value with a "switch" clause, like FSImageFormatProtobuf.Loader#loadInternal(), as:

switch (SectionName.fromString(n))

NPE will be thrown here.