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Unless you have a specific reason to use an application-managed Entity Manager, we recommend using the Session Facade design pattern (discussed in 12.2.3) with CMT, and a container-managed Entity Manager.The EJB 3 incarnation of session beans are lightweight POJOs, which make life easier by not requiring the developer to manage the life-cycle of entity managers or transactions. You might have some applications, such as a Swing or SWT application, for which you’d prefer to use JPA outside the EJB 3 container.For instance, you should avoid dependency injection. If you’re planning to use JPA from a managed class like a servlet, you may be tempted to inject an instance of an Entity Manager by using the @Persistence Con-text annotation like this: If you use this and test your application, it will probably run successfully in your first few attempts.However, you’ll likely run into issues when more users try to access the servlet at the same time.You may not need the power or additional complexity of EJBs for every Java EE application, and therefore decide to forego session beans on occasion.For instance, you may choose to stick with POJOs and servlets to implement business logic, and include the entities directly in the web module (or WAR).You can make your entity classes available to your web module in one of two ways: ■ Place entity classes directly in WEB-l NF/classes.
As you know, we don’t typically recommend using an application-managed Entity Manager, but in some cases it’s your best choice.
In this tutorials, it provides many step by step examples and explanations on using Struts 1.x MVC framework. :) Let’s go through a quick start to understand about the Struts 1.x framework.
In Struts validator framework, it provides many generic methods (required, maxlength, minlength..) to validate the form components, it makes your validation code more standardize and easier to maintain.
Bear in mind that the JNDI lookup mechanism can be used in any nonmanaged or managed class.
To use a container-managed Entity Manager, you must first establish the references to the persistence unit using either the @Persistence Context annotation at the class level or the persistence-context-ref element in