Which project manager or task manager is best for integrating with a java application?

Question

Java

What do you want?
There is an application written in java, I want to be able to deploy a task scheduler (something like jira) on my server, which would provide a fairly rich API that allows the application to manage the life cycle of tasks and exchange data, namely

• create tasks
  
• change task status
  
• assign tasks
  
• be able to import users from the application
  
• notification of users about changes in the status of tasks by email
  
• it is desirable to have a protocol for exchanging messages between the application and the manager
  

Requirements

• open source / the ability to buy the source code / good customization (in general, you really need the ability to customize the task manager for yourself)
  
• the ability to install on your hosting
  
• ability to create nested tasks
  
• it is desirable to be able to independently set a list of attributes for created tasks (as, for example, in jira, you can specify a list of attributes that characterize the task for a task, indicate which of them will be mandatory, specify the types of values ​​​​for these attributes)
  
• more or less developed own web interface with a built-in editor and other delights of modern life
  
• role-based security (separation of users by roles with different access levels)
  
• analytics
  
• maybe you need something else that is now eluding my eyes))
  

Actually, now I am considering redmine as the main candidate , however, I cannot yet accurately assess how smoothly it will integrate with the application. Perhaps readers have experience and you are ready to share it, for which I will be very grateful.
Jira comes to mind as the second contender, which we use in the software development process, however, we use jira as a service, of course, there is no experience of interacting with this task manager from the application. And for the functionality for which the task manager is supposed to be used (a kind of service for issuing tasks to users serving business processes modeled by the application), you need to deploy it on your own hosting. Although, as I understand it, jira is a java application, unlike redmine, written in ruby, and perhaps there are already good solutions for jira that allow it to be smoothly linked with another java application.
In general, please share your thoughts on this, what is better to choose (naturally, not only from the above), and how best to integrate it with a java application.

Answer 1

Jira or YouTrack

Answer 2

By the way, redmine also has a good rest api
, but it still confuses me that it is a ruby ​​application, and we are not very familiar with ruby ​​((