Add documentation on how to specify associations on the creation/modification of entities in a single HTTP invokation [DATAREST-1036]

[spring-projects-issues]

Aaron Loes opened DATAREST-1036 and commented

There is supposedly a means of creating an entity and associations with other entities in a single HTTP call. However, there are no examples of how to do this in the documentation or any of the linked guides.

In an old bug report (DATAREST-327), i was informed that this could be done by providing the url of the entity to be associated as the value of the field for single references and in a list for multiple association for the purposes of situations where there are non-optional relationships to other resources. That bug report is old and its likely that the method of specifying associations during entity creation has since changed.

Please add documentation that shows examples of how to structure the payload to include associations to already created entities or respond if this is no longer a feature of SD Rest.

Thank you

---

No further details from DATAREST-1036

[spring-projects-issues]

Aaron Loes commented

i should specify that i did try what was suggested in that bug comment and an error was thrown stating that the system "could not construct instance of <my class>: no String-argument constructor/factory method to deserialize from String value (<uri to entity to associate>)

It looks like this was also specified as a means on stackoverflow here (http://stackoverflow.com/a/26426909) so it must have worked at some point.

Using version 2.6.1 of SD Rest

[spring-projects-issues]

Aaron Loes commented

i figured out why i was getting the error. I still think the documentation should at least comment on how this is done. Or even possibly the guide for showing how to use the API with CURL

[ruthst00]

@odrotbohm, upvoting because I checked the examples offered under spring-data-rest and spring-data-examples and don't see any that provide sample code for how to create an entity and associations with other entities in a single HTTP call.

That said, there are several Stack Overflow articles (e.g., here and here) that provide examples, however with varying degrees of success. I'm not sure if these have been tested and they are probably out of date.

One could argue that creating a parent record first, then a child record (or the other way around) with two HTTP calls is a reasonable workaround, but if the Spring Data Rest framework supports creating both records with one call, then why not offer an example for how to do this correctly and save folks a little time?

I believe a "multi-entity association" example should be added to spring-data-examples and updated with subsequent releases of Spring Data Rest. Once that's complete, I believe this issue can be closed. I don't believe the fix for this issue belongs in this repo.

[ruthst00]

@odrotbohm, I submitted a PR here for a sample app that attempts to address this request. Can you please review? Once that PR is approved and merged, this issue can be closed.