Java web based search engine?

Question

Java

Dear toasters, hello. I need your help.
It is necessary to make an application: Text files are loaded into the system, the user enters a search query - a task is set for execution in the system: a search is carried out in all uploaded files, each line is selected from each document in which the search phrase occurs and a final document is formed in which: all found strings, indicating the document in which they were found.
I don't know how to upload files to the file system and search them. I have a very poor idea of ​​how to wrap all this in a servlet, and even more so, I have almost no idea how to use multithreading.
How to do it please tell me

Answer 1

It is necessary not to load into the file system, but into Full text search engine, ElasticSearch or Sphinx