Spring data JPA consumes all the connection objects

I have a scenario where in data is uploaded from excel sheet to mysql db. I am using spring data jpa. And the service calls the entities recursively after stuffing them with data taken from excel sheet to save in db. This creates "unable to acquire jdbc connections" after a certain load.

I tried with @Transactional to know advantage. Then I am thinking of using EntityManager manually in code and control transaction boundary so that all recursive save calls of entities happen within one transaction and thereby one connection object. I just wanted to check would it be a nice idea or is there any other approach I should take which is more performant. Needless to say anyhow I have to do it through entities.

My answer is completely based on the assumption that the way of implementing the requirement is faulty as there isn't any code shared in the question.

By your approach, yes you will run out of the connection as the entity population would surely be much faster than persisting that entity in the database and since you are doing it recursively your application will run out connections at one point of time if the amount of the data is very high, numbers are certainly a factor here.

The other approach I would prefer is that you can prepare your entities(Assuming all the data is for a common entity class) and store in a collection, once it is ready you can persist all of it in one transaction using saveAll() method.
If the data is not for common entities you can create multiple lists of different entities and initiate the DB operations after processing the excel sheet.