Usage of REST API for migration of defects from an external system

[RAMANIGANTH_VELUR]

We are currently working on migration of defect from an external application to JIRA 7.0. We understand preferred way to import the defects is using JIM. However, we are analyzing the option using REST API to create all the issues that are to be migrated, as JIM introduces manual intervention and the requirement is to have a one click migration. WIth this context we have below questions

While importing issue using JIM, the utility provides the creation of users in JIRA as part of the data import to the user picker fields. REST API expects the user to be available, active and having appropriate permission in the project. Do we have any workaround to mimic the functionality of JIM in REST API while creating the issue.?

Similar concerns are for fields with select options, components and versions. Do we have any suggestion to create those entries on the fly while creating issue using REST API?

[Nic Brough -Adaptavist-]

The REST API does not have the administrative functions for updating fields, like JIM does.  To use REST to do this, you've got to have all the supporting data in place before you can import. 

[RAMANIGANTH_VELUR]

Thanks Nic for your immediate response. I have seen the same behavior with JIRA CLI (BoB Swift). Is my understanding correct that the CLI tool also works in the same way as REST API.? 

[Nic Brough -Adaptavist-]

Not quite the same way, but it does use REST.  It has an add-on component that allows for more calls than plain REST allows.

[RAMANIGANTH_VELUR]

Thanks a lot Nic. We are going ahead with JIM for data, attachments and link imports.