Few days ago, during our regular code review, one of my colleagues raised a question what would happen – and if it’s even possible – when a CDI Observer (so a method with parameter annotated @Observes) would be invoked multiple times at the same time for different event instances. In other words, after producing few events, is it possible that the following method will be processed by more than one thread at the same time:...
Java EE 7 has been recently accepted by the Executive Committee. This means that soon we should have Java EE 7 application servers available on the market. One of the specifications that constitutes Java EE 7 is JMS 2.0. Some interesting improvements were introduced since version 1.1. JMS has a lot of weird stuff like: Connection#createSession(boolean transacted, int acknowledgeMode) method. First method argument (transacted) defines if the session should be transacted....
Despite the fact that EJB inheritance sometimes uses Java inheritance – they’re not always the same. Just as you could read in my previous post, EJB doesn’t have to implement any interface to expose a business interface. The other way around is also true – just because EJB is implementing some interface or extending other EJB doesn’t mean it exposes all or any of its views. Let’s say we want to have some basic EJB exposing remote business interface....
This post will talk about possible ways of defining EJB views using annotations (I’ll just mention about using EJB Deployment Descriptor at the end.) I’ll focus on the most current EJB 3.1 views omitting legacy local, remote and home interfaces. Therefore, we can choose between: remote business interface view, local business interface view, no-interface view. I won’t discuss functional differences between those views but rather focus on possible ways of defining them....
Let’s start with a short quiz. TxMergeBean is a SLSB that uses CMT and EntityManager. Assume the following local and remote business interfaces: public interface TxMergeCommon { void methodA(); void methodB(MeineEntity entity); } @Local public interface TxMergeLocal {} @Remote public interface TxMergeRemote {} and the following SLSB: @Stateless public class TxMergeBean implements TxMergeRemote, TxMergeLocal { @PersistenceContext private EntityManager em; @EJB private TxMergeLocal self; @Resource private SessionContext sctx; public void methodA() { MeineEntity entity = new MeineEntity("methodA"); em....
Being in EJB and JPA world using CMT (Container Managed Transactions) is very comfortable. Just define few annotations to demarcate transaction boundary (or use the defaults) and that’s it – no fiddling with manual begin, commit or rollback operations. One way to rollback your transaction is to throw non-application exception (or application exception with rollback = true) from your EJB’s business method. It seems simple: if during some operation there is a possibility that an exception will be thrown and you don’t want to rollback your tx than you should just catch this exception and you’re fine....
JPA specification defines few types of EntityManagers / Persistence Contexts. We can have: extended and transactional-scoped EntityManagers, container-managed or application-managed EntityManagers. JTA or resource-local EntityManager, Besides the above distinction, we also have two main contexts in which EntityManager / Persistence Context can exist – Java EE and Java SE. Not every option is available for Java EE and not every is possible in Java SE. In the rest of the post I refer to the Java EE environment....
This post describes some of the pitfalls when coping with intercommunication between different modules (EAR, WAR, EJB-JAR) deployed in the same Java EE 6 Application Server. The problem The problem is as follows: you have two modules (let’s take the EARs as an example) that are deployed in the same JVM / Application Server: App1.ear and App2.ear. App1.ear contains: service.jar; it’s an EJB-JAR with the business logic of the application, service-api....
In this post you can find often used Java EE 6 configuration files (along with their schema declarations to aid your IDE’s code assistant): CDI Name: beans.xml Version: 1.0 Content: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/beans_1_0.xsd"> </beans> JPA Name: persistence.xml Version: 2.0 Content: <?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0"> </persistence> Servlets, JSP, EL Name: web.xml Version: 3.0 Content: <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java....
Java EE 6 brings a lot new features. Among the others there is the concept of profiles. Java EE starts with the definition of two: Full and Web Profile. The idea is to create separate and more specialized set of services that better suits your job. E.g. if you only want to use Servlets, JSP and add some EJB’s – do you really need full-blown application server with JMS, JMX, CORBA, JAX-WS and a lot of other abbreviations?...