Expose the ObjectMapper to allow custom JSON serializer/deserializers about elasticsearch-hadoop

[costin]

Can you be more specific? I assume you are referring to the configuration of OM to be tweaked (specifically to register extra inspectors) as exposing... well, that's a bit difficult considering the Input/OutputFormat are instantiated by Hadoop on each node .

[tzolov]

Sorry for the vague description but I've assumed it correct.
One way to do it is to add an additional (ES_OBJECTMAPPER_CLASS) parameter to Job Configuration. This param will hold the class name of a custom ObjectMapper implementation. Later (if provided) is instantiated by the RestClient using reflection. If the param is not set then a normal ObjectMapper is created. The custom OM implementation is distributed via the DistCache similar to the es-hadoop.jar.

The following patch should illustrate the approach:
tzolov@8fb1fb6

[tzolov]

Just merged with the upstream.
The new Settings class simplifies the custom OM implementation:

• new ConfigurationOptions.ES_OBJECTMAPPER_CLASS constant.
• Extended RestClient constructor and new createObjectMapper(String className) method (
  https://github.com/tzolov/elasticsearch-hadoop/blob/objectmapper/src/main/java/org/elasticsearch/hadoop/rest/RestClient.java)

[costin]

Closing this issue as won't fix since the object mapper has been replaced internally with stream parsing for core communication with ES. OM is still used but sparingly and only for internal use.