You have injected the EntityManager via parameter $em. This is generally not recommended as it might get closed and become unusable. Instead, it is recommended to inject the ManagerRegistry and retrieve the EntityManager via getManager() each time you need it.
The EntityManager might become unusable for example if a transaction is
rolled back and it gets closed. Let’s assume that somewhere in your application,
or in a third-party library, there is code such as the following:
functionsomeFunction(ManagerRegistry$registry){$em=$registry->getManager();$em->getConnection()->beginTransaction();try{// Do something.$em->getConnection()->commit();}catch(\Exception$ex){$em->getConnection()->rollback();$em->close();throw$ex;}}
If that code throws an exception and the EntityManager is closed. Any other
code which depends on the same instance of the EntityManager during this
request will fail.
On the other hand, if you instead inject the ManagerRegistry, the getManager()
method guarantees that you will always get a usable manager instance.
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The
EntityManagermight become unusable for example if a transaction is rolled back and it gets closed. Let’s assume that somewhere in your application, or in a third-party library, there is code such as the following:If that code throws an exception and the
EntityManageris closed. Any other code which depends on the same instance of theEntityManagerduring this request will fail.On the other hand, if you instead inject the
ManagerRegistry, thegetManager()method guarantees that you will always get a usable manager instance.