Note: I'm not actually sure whether this is intentional or not. If it is, I didn't see any mention of it, but it feels like something that should explicitly be mentioned in the Spring Batch 6 migration guide. The docs do mention changes to the Job Parameter APIs, but they don't seem to indicate that these changes will affect persisted data.

DefaultJobKeyGenerator was refactored here: 86dh@2d9bbae#diff-6e38cfa7139610dfc635ee6285d477356902cd01916529efa2fbca15ab6b1b01

The refactor changes the format of generated job keys, breaking backward compatibility with keys stored in the job repository database for existing job instances.

Old format: key={value=..., type=..., identifying=...}
New format: JobParameter{name='...', value=..., type=..., identifying=...}

Jobs with the same parameters will generate different keys, potentially preventing applications on Spring Batch 6 from finding existing job executions.