First, you have to understand how the beans are created and handled on the server. For stateless session beans the server can maintain a variable amount of instances in a pool. Each time a client requests such a stateless bean (e.g. through a method) a random instance is chosen to serve that request. That means … Read more
Stateless Session Beans (SLSB) are not tied to one client and there is no guarantee for one client to get the same instance with each method invocation (some containers may create and destroy beans with each method invocation session, this is an implementation-specific decision, but instances are typically pooled – and I don’t mention clustered … Read more
It is currently indeed a bit confusing as there are now multiple component models in Java EE. They are CDI, EJB3 and JSF Managed Beans. CDI is the new kid on the block. CDI beans feature dependency injection, scoping and an event bus. CDI beans are the most flexible with respect to injection and scoping. … Read more
List is an interface. Interfaces cannot be instantiated. Only concrete types can be instantiated. You probably want to use an ArrayList, which is an implementation of the List interface. List<Product> products = new ArrayList<Product>();
Yes, you can freely mix both CDI and EJB and achieve some great results. It sounds like you are using @WebService and @Schedule, which are good reasons for adding EJB to the mix. There’s a lot of confusion out there, so here is some general information on EJB and CDI as they relate to each … Read more
Some projects have all data twice. Once as domain objects, and once as data transfer objects. This duplication has a huge cost, so the architecture needs to get a huge benefit from this separation to be worth it.
Why really use them? (Why not just stick to POJO?) IF you need a component that accesses the database, or accesses other connectivity/ directory resources, or is accessed from multiple clients, or is intended as a SOA service, EJBs today are usually “bigger, stronger, faster (or at least more scalable) and simpler” than POJOs. They … Read more
The @EJB is used to inject EJB’s only and is available for quite some time now. @Inject can inject any managed bean and is a part of the new CDI specification (since Java EE 6). In simple cases you can simply change @EJB to @Inject. In more advanced cases (e.g. when you heavily depend on … Read more
(Updated Feb 2022) First of all, “Java EE” has since Sep 2019 been renamed to “Jakarta EE“, starting with version 8. Historically, there was also the term “J2EE” which covered versions 1.2 until 1.4. The term “Java EE” covered versions 5 until 8. See also Jakarta EE, History on Wikipedia. Is Jakarta EE just a … Read more
I’m very new to Java EE and I’m trying to understand the concept of Local interfaces and Remote interfaces. In the initial versions of the EJB specification, EJBs were “assumed” to be remote components and the only way to invoke them was to make a remote call, using RMI semantics and all the overhead it … Read more