@MappedCollection is not working properly for save flow

[ZhuravelStanislav]

There is an issue with id generation for @MappedCollection (save flow is affected), insert queries for inner entities with id=null generated as 0,1,3...(generated id equals to index of the element in the collection. Java 17, Myslq, spring-boot-starter-data-jdbc:2.5.5

[schauder]

Please provide a Minimimal Reproducable Example, preferable as a Github repository. Make sure to include the database, either as an in memory database or if that is not possible using Testcontainers.

[ZLStas]

Have a look here pls https://github.com/ZLStas/data-jdbc-issue/tree/master

[schauder]

By having a repository for B you are making it an aggregate. But. if you put a reference (via a collection) to B in A you are making it part of another part. This does not work.

If B is an aggregate root it should only be referenced by id.

If B is part of aggregate A it must not be referenced from any entity outside A.

See also https://spring.io/blog/2018/09/24/spring-data-jdbc-references-and-aggregates

[ZhuravelStanislav]

Thank you very much @schauder for the update, I believe I still need to master my knowledge about DDD, it is much clearer to me now, but I still struggle with one point, I have deleted repo for B, which actually makes A as an aggregate (case 2 "If B is part of aggregate A it must not be referenced from any entity outside A.") if I save A with two B inside, I have "Duplicate entry '1' for key 'PRIMARY'", I believe I am lacking some understanding where @MappedCollection should be used, could you pls clarify it to me, or it's actually a bug? see https://github.com/ZLStas/data-jdbc-issue/blob/example2/src/test/java/com/example/datajdbcissue/AServiceTest.java

[okjesse]

Thank you very much @schauder for the update, I believe I still need to master my knowledge about DDD, it is much clearer to me now, but I still struggle with one point, I have deleted repo for B, which actually makes A as an aggregate (case 2 "If B is part of aggregate A it must not be referenced from any entity outside A.") if I save A with two B inside, I have "Duplicate entry '1' for key 'PRIMARY'", I believe I am lacking some understanding where @MappedCollection should be used, could you pls clarify it to me, or it's actually a bug? see https://github.com/ZLStas/data-jdbc-issue/blob/example2/src/test/java/com/example/datajdbcissue/AServiceTest.java

hi,I found the same question,do you find the anwser or maybe this is a bug!

[schauder]

This turned into a discussion about correct usage. Those should be asked at Stack Overflow and be tagged with spring-data-jdbc. It also doesn't help that it is on a closed issue.
By using Stack Overflow, the community can assist and the questions and their answers can more easily be found using the search engine of your choice.

Please create a question on Stack Overflow and leave a link here. I'll promise to take a look.

[okjesse]

This turned into a discussion about correct usage. Those should be asked at Stack Overflow and be tagged with spring-data-jdbc. It also doesn't help that it is on a closed issue. By using Stack Overflow, the community can assist and the questions and their answers can more easily be found using the search engine of your choice.

Please create a question on Stack Overflow and leave a link here. I'll promise to take a look.

OK,Thank you~~