Putting a mapping with an empty request body throws a NullPointerException

[dtdesign]

I have been struggling with an issue lately caused by my own fault of providing a valid request body when attempting to add a mapping to an existing index. Attempting to do so will yield a NullPointerException:

[2014-09-01 20:08:31,486][DEBUG][action.admin.indices.mapping.put] [Prototype] failed to put mappings on indices [[my_index]], type [my_type]
java.lang.NullPointerException
    at org.elasticsearch.common.xcontent.XContentFactory.xContent(XContentFactory.java:137)
    at org.elasticsearch.common.xcontent.XContentHelper.convertToMap(XContentHelper.java:113)
    at org.elasticsearch.common.xcontent.XContentHelper.convertToMap(XContentHelper.java:101)
    at org.elasticsearch.index.mapper.DocumentMapperParser.parseCompressed(DocumentMapperParser.java:181)
    at org.elasticsearch.index.mapper.MapperService.parse(MapperService.java:387)
    at org.elasticsearch.index.mapper.MapperService.parse(MapperService.java:377)
    at org.elasticsearch.cluster.metadata.MetaDataMappingService$5.execute(MetaDataMappingService.java:540)
    at org.elasticsearch.cluster.service.InternalClusterService$UpdateTask.run(InternalClusterService.java:309)
    at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:134)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

The issues is caused by https://github.com/elasticsearch/elasticsearch/blob/a059a6574a1c270ccc28ddec1671888fb0cfba28/src/main/java/org/elasticsearch/common/xcontent/XContentFactory.java#L213 which returns null if the input stream is empty. While this is fine, the real problem lies in XContentHelper.convertToMap() which does not properly check for null.

https://github.com/elasticsearch/elasticsearch/blob/a059a6574a1c270ccc28ddec1671888fb0cfba28/src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java#L111-L113

To be fair, this isn't really a bug and I'm more like asking to yield a proper exception in case a developer is as dumb as me and fails to provide a proper request body.

[cfontes]

Could you provide some examples of the messages you used?

[dtdesign]

@cfontes The request was PUT http://127.0.0.1:9200/my_index/_mapping/my_type, message body had a length of 0.

[rjernst]

Found the problem and fixed. Thanks for the report!