First of all, “J2EE” is an obsolete abbreviation, it is now simply called “Java Enterprise Edition” or Java EE. Contrary to the servlet container (e.g. Tomcat), “full” Java EE application servers contain also an EJB container. EJB are Enterprise Java Beans and you can read a lot about them for example here (chapter IV). EJBs … Read more
EJBs are built on top of RMI. Both imply Java clients and beans. If your clients need to be written in something else (e.g., .NET, PHP, etc.) go with web services or something else that speaks a platform-agnostic wire protocol, like HTTP or XML over HTTP or SOAP. If you choose RMI, you don’t need … Read more
I am not sure this is supposed to work. So either: Option 1: Use the injection provider SPI Implement a provider that will do the lookup and inject the EJB. See: @EJB injection. Example for com.sun.jersey:jersey-server:1.17 : import com.sun.jersey.core.spi.component.ComponentContext; import com.sun.jersey.core.spi.component.ComponentScope; import com.sun.jersey.spi.inject.Injectable; import com.sun.jersey.spi.inject.InjectableProvider; import javax.ejb.EJB; import javax.naming.Context; import javax.naming.InitialContext; import javax.ws.rs.ext.Provider; import java.lang.reflect.Type; … Read more
The rules are (from memory): Bean has a @LocalBean annotation -> bean has a no-interface view Bean has a @Local annotation -> bean has a local view Bean has a @Remote annotation -> bean has a remote view Bean has no view annotations, but directly implements an interface which has a @Local annotation -> bean … Read more
Remote client view When your EJB and its clients will be in a distributed environment – meaning EJBs and clients will reside on separate Java virtual machines. Example : EJBs hosted on a WebSphere Application Server and Servlets that consume EJB APIs hosted on a Tomcat server. Local client view Only when it is guaranteed … Read more
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