Initially, after reading books on the subject, I firmly believed that the algorithm for working with a database from a servlet is as follows: create a connection -> connect to the database -> form a request -> send the request to the database -> get the query results -> process them -> close connection -> OK.

Now, with a better understanding of the practical side, I realized that nobody does it that way, and everything happens through a connection pool according to the following algorithm:

initialize the servlet -> create a connection pool -> a request comes from a user -> take a free connection from the pool -> form a request -> send the request to the database -> get the query results -> process them -> return the connection back to the pool -> ok.

Now I have this problem: We have 100 users, they are divided into 10 groups, each group has it's own username and password to connect to the database. Moreover, each group may have different rights to the database. How am I supposed to use a connection pool in this situation? If I understand correctly, a pool is nothing more than just a group of similar connections with a single login and password. And here I have 10 pairs of username / password. It looks like I cannot use the pool in this situation. What should I do?