Serguey Asael Shinder: Spring Batch gives the Mongo job repository a collection prefix
Spring Batch 6.1.0-M2 was announced on 24 September 2026 at https://spring.io/blog/2026/09/24/spring-batch-6, the second milestone of the 6.1 line and, by the team's own description, one that carries breaking changes on top of 6.1.0-M1.
Two changes are worth reading past the headline.
The MongoDB job repository takes a configurable collection prefix. Until now the JDBC repository had a table prefix and the Mongo one did not, so two applications pointed at the same database shared the same collections whether or not that was intended. The prefix defaults to BATCH_, which means nothing changes for an existing deployment, and setting it allows several applications to run against one MongoDB database or one environment to be kept apart from another.
The default conversion service is now built on Spring Framework's DefaultFormattingConversionService, reached through a new ConversionServiceFactory utility, in place of the hand-written converters that used to do the job. The announcement says job parameter formats are preserved; the previous date and time converters are deprecated in favour of the factory. Separately, the async processing APIs and local chunking have moved into spring-batch-core.
The part that matters on an upgrade
The prefix default is the interesting piece of design. BATCH_ is chosen so that no existing application notices the feature exists - the collections it already writes keep their names - while the capability that was missing becomes available to anyone who needs it. A new configuration option that changes behaviour by default would have made this milestone an incident for every Mongo user; one that changes nothing until set is a feature.
The conversion service change is the opposite shape and deserves a test rather than trust. Replacing hand-written converters with a general framework service preserves the documented formats, and the formats that were never documented are the ones to check: a job parameter that round-tripped through a bespoke converter may now travel through a different one with the same name and a different edge case. Deprecations name what to move to, which is ConversionServiceFactory.