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How to deal with thread in background processing java spring boot?

I want to download file after query but the time is too long, so my company said I should let the process in background.
For that I create thread when user call method, it will generate file and send to email of customer.
But the problem is about my thread, I also test function for sendemaildownload (it also includes the function which I use to query), I'm quite sure this problem from the way I create the thread.
This is what it says to me when I'm logging the error on creating the thread:
Exception in thread "Nathan-Transportation1" java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
Is there any way to fix it? I want to understand why it happend when I create my thread pool.

Try using #Async annotation.
For more information see here

This error message indicates that you are attempting to access request-scoped data (for example, request attributes) outside of the context of an HTTP request.
You can try the following solutions to this problem:
To expose the current request and make it accessible to your code,
use a RequestContextListener or RequestContextFilter.
To execute tasks in a background thread, use Spring's TaskExecutor interface, which will handle the necessary context management for you.
Here are some links that may be of interest to you:
RequestContextListener
RequestContextFilter
TaskExecutor

Using spring session scope without session

I have web application where I defined session scoped UserDetail. The problem is that I also have some Quartz jobs that should use UserDetail bean. When job is run I get:
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'scopedTarget.userDetails': Scope 'session' is not active for the current thread; consider defining a scoped proxy for this bean if you intend to refer to it from a singleton; nested exception is java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
Inside job I need to inject some "technical user" details. Is it possible to properly handle situation when session is not present? Maybe any conditional injection?
EDIT 1
To clarify. I dont want to have session in my job service. This job modifies data and some audit log based on user data is saved to database. Normally user data comes from session but in job I need to provide some "static" technical user data. Any ideas?

Quartz does not know anything about "sessions", so if you want your background job to know the user that submitted the job, you have to pass that information to the job, likely in the DataMap of the trigger.

How does a Shiro enabled web application handle CacheExceptions

I have a question about handling org.apache.shiro.cache.CacheException.
What is shiro's responsibility when a cache exception occurs? This RTE ripples through the whole stack, but I'm unclear where it is handled and in what manner.
Can a shiro enabled web application recover?
Is the cache manager reinitialised?
Do I have to restart the application when a cache exception occurs?
For example, a timeout exception or a failed to connect to node exception occurs on cache.get(key). What's the expected outcome apart from bubble to the stop and die?
Thanks

I have checked all usages of CacheException and the only thing shiro does is throw it. It never gets catched let alone handled.
So the only expected outcome is to "bubble to the stop and die".
What you can do about it is have a servlet filter in front of shiro that catches this exception, then get a hold of the CacheManager instance (how you do that depends on your setup) and call cacheManager.getCache().clear() so the cache is reset.

Could not initialize proxy - no Session

I've got an error that looks like this:
Could not initialize proxy - no Session
I'm working with java, hibernate and spring. This error comes up when trying to generate a PDF document, and I'm following the next steps to generate it on the fly and store in the database.
I sent a request to the app through a POST method. This generates the PDF on the fly and shows to the user.
Just after that request I send another, but through an ajax a request. This will generate the same PDF but will save it in the DB.
The error shows that a query could not be executed due to "could not initialize proxy - no Session" error.
Is there something that am I doing wrong, calling the same methods twice from the same user session? Could it be that the session is closed before both requests have finished?
Hope someone can help me to understand what is happening.

Your problem is that the hibernate Session lives only for one request. It opens in the start of the request and closes at the end. You guessed the answer: Hibernate session is closed before both requests are finished.
Exactly what is happening? Your entity objects live during both requests. How? They are stored in the HTTP session (which is a different thing called session) You don't give much information about the framework you are using, so I can't give you more details, but it is certain that the framework you are using somehow keeps your entities in the HTTP session. This is how the framework makes it easy for you to work with the same objects for more than one requests.
When the processing of the second request starts, the code is trying to access some entity (usually an element of a collection) that is lazily initialized by hibernate. The entity is not attached to a hibernate session, and so hibernate can't initialize the hibernate proxy before reading it. You should open a session and re-attach your entity to it at the beginning of the ajax request processing.
EDIT:
I will try to give a brief explanation of what is happening behind the scene. All java web frameworks have one or more servlets that handle the requests. The servlet handles each request (HttpRequest) by creating a new thread that will finally produce the response (HttpResponse). The method that processes each request is executed inside this thread.
At the beginning of the request processing your application should allocate the resources that it needs for processing (Transaction, Hibernate session etc). At the end of the processing cycle these resources are released (Transaction is committed, hibernate session is closed, JDBC connections are released etc). Lifecycle of these resources could be managed by your framework, or could be done by your code.
In order to support application state in a stateless protocol as HTTP, we have the HttpSession object. We (or the frameworks) put on HttpSession the information that remains relevant between different request cycles of the same client.
During the processing of the first request hibernate reads (lazily) an entity from the database. Due to lazy initialization some parts of this object's structure are hibernate proxy objects. These objects are associated with the hibernate session that created them.
The framework finds the entity from the previous request in the HttpSession object when you try to process the second request. Then it is trying to access a property from a child entity that was lazily initialized and now is a hibernate proxy object. The hibernate proxy object is an imitation of the real object that will ask its hibernate session to fill it with information from the database when someone tries to access one of its properties. This what your hibernate proxy is trying to do. But its session was closed at the end of the previous request processing, so now it doesn't have a hibernate session to use in order to be hydrated (filled with real info).
Note that it is possible that you have already opened a hibernate session at the beginning of the second request, but it isn't aware of the entity that contains the proxy object because this entity was read by a different hibernate sesion. You should re-attach the entity to the new hibernate session.
There is a lot of discussion about how to re-attach a detached entity, but the simplest approach right now is session.update(entity).
Hope it helps.

How to manage authenticated status in EJB3?

There is a task of managing desktop client session status:
Ensure only single client is "connected".
Force client logout - kill session.
Kill client session on timeout due to inactivity.
Server-side is JBoss and EJB3. How to achieve such task?

You can use Singleton Pattern here, once initialized, deny subsequent requests thereafter in synchronized method by using delegate to access interfaces (local/remote).
Maintain you own idle-timer & start it at event occurence either mouse/key for your window.
On timeout, you can de-reference the initialized objects & redirect to login.

Method annotated with #Remove allows to kill EJB3 session.
We can ensure uniqueness of session by adding it to static (or other unique) container and check for existence before returning it for the new client. If existing session found, we throw an exception for the user.
So, this answers my questions, I think.