4.3.1. DataManager vs. EntityManager

Both DataManager and EntityManager can be used for CRUD operations on entities. There are the following differences between these interfaces:

DataManager EntityManager

DataManager is available on both middle and client tiers.

EntityManager is available only on the middle tier.

DataManager is a singleton bean. It can be injected or obtained via AppBeans.get().

You should obtain a reference to EntityManager through the Persistence interface.

DataManager defines a few high-level methods for working with detached entities: load(), loadList(), reload(), commit().

EntityManager mostly resembles the standard javax.persistence.EntityManager.

DataManager in fact delegates to DataStore implementations, so the DataManager features listed below apply only to the most common case when you work with entities located in a relational database:

DataManager EntityManager

DataManager always starts new transactions internally.

You have to open a transaction before working with EntityManager.

DataManager loads partial entities according to views. There are a few exceptions, see details here.

EntityManager loads all local attributes. If a view is specified, it affects only reference attributes. See details here.

DataManager executes only JPQL queries. Besides, it has separate methods for loading entities: load(), loadList(); and scalar values and aggregates: loadValues().

EntityManager can run any JPQL or native (SQL) queries.

DataManager checks security restrictions when invoked on the client tier.

EntityManager does not impose security restrictions.

When you work with data on the client tier, you have only one option - DataManager. On the middleware, use EntityManager when you need to implement some atomic logic inside a transaction or if the EntityManager interface is better suited to the task. Otherwise, on the middleware you can use both.

If you need to overcome restrictions of DataManager when working on the client tier, create your own service and use EntityManager to work with data. In the service, you can check permissions using the Security interface and return data to the client in the form of persistent or non-persistent entities or arbitrary values.