Make the documentation about the customization of spring data mongodb converters more prominent

[hadjiski]

Make the documentation about the customization of spring data mongodb converters more prominent

[wilkinsona]

Unfortunately, it isn't practical to provide examples for every bean that's auto-configured showing how it can be overridden as it would make the documentation overly verbose. Instead, we prefer to take advantage of the fact that Spring Boot is open source and that you can use the condition evaluation report that see what is being auto-configured and why.

If you start an app that uses Spring Data MongoDB with --debug, you'll see something similar to the following in the output:

============================
CONDITIONS EVALUATION REPORT
============================


Positive matches:
-----------------

…

MongoDataConfiguration#mongoCustomConversions matched:
      - @ConditionalOnMissingBean (types: org.springframework.data.mongodb.core.convert.MongoCustomConversions; SearchStrategy: all) did not find any beans (OnBeanCondition)

From this you can learn that mongoCustomConversions was auto-configured because there was no existing MongoCustomConversions bean in the context. This means that it will back off if you define your own. You can also look at the problem from those other side and start with the auto-configuration classes that are listed in the appendix.

The benefit of this approach is that it is generally applicable to any auto-configuration. Thanks anyway for the suggestion but we feel that our current approach is more practical approach as it doesn't require individual examples in the reference documentation for every single different bean that Spring Boot can auto-configure.