Automatically create review sub-tasks and assign to other users?

My team is setting up a JIRA Server. We do code reviews on new features and bug fixes, and I was wondering if there is a way that we could automatically set up JIRA to generate two subtasks and assign those to reviewers when transitioning to a review state. I have done Java development in the past, so would this be something I could create a plug in to do? Or would I need to buy an existing app from the marketplace?

You can certainly do this with a number of existing apps, such as JMWE (with the Create Issue(s) post-function), ScriptRunner (with a scripted post-function), JSU, etc.