如何在呈现页面之前获取线程响应

Question

I have an application which require File Operation , that need to be done as concurrently

1. If a user try to READ a file , other users cant perform WRITE operation
2. If a user try to WRITE to file , other user cant perform READ Operation

business logic applied :

Created Thread using Runnable Interface and added Synchronized READ Methods to read property file from remote location and put it into session /request object

• issue : while starting a new thread the response get finished (since thread is independent path of execution) .so the property values are not available

How to get the thread response before the page get displayed ? I heared that we can use Callable Interface , please share the best approach suited in this situation.

Answer 1

Making a thread in servlet in this way(initiate a Runnable and run it by JVM directly) is completely non-sense and not recommended for sake of memory leak, and unmanaged context.

It's completely nature you get undefined/nonstable states of request/session context by the new thread.

Since the thread gets started asynchronously, the servlet/server context continue its working and response to the client, and the request context is no more valid.

You may do it by a mutex, since the servlet context is multi-threaded by default, and you may not never and never run threads that way please, and if you do, you may do it by session context listeners to handle events and prevent any possible memory leak.

You may either wait(block) the response while the related context(file) is locked, which is not so logical. Or inform the user the requested file is being locked becasue of another read/write operation.
And of course you need a push like method(like websockets) or alternatives(check status by ajax or reloading) to check the latest related context status.

And the most logical way is, you need to do it in queue mode, and just make sure the part of the file need to be changed is valid with latest state.