It seems there is no support for configuring hdp:job with multiple mappers.
Going over JobFactoryBean.java I didn't observe any support for that.
There are cases where one job contains multiple mappers attached to single reducer. Usually it is done using hadoop MultipleInputs class when configuring a job using java.
This would be great to have this configuration ability available also from spring. It would be extremely beneficial also to spring-hadoop test module.