Minor Description
In the file hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/serializer/SerializationFactory.java, we grab the IO_SERIALIZATIONS_KEY config as Configuration#getStrings(…) which does not trim the input. This could cause confusing user issues if someone manually overrides the key in the XML files/Configuration object without using the dynamic approach.
The call should instead use Configuration#getTrimmedStrings(…), so the whitespace is trimmed before the class names are searched on the classpath.