Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A Java EE application or a Java Platform, Enterprise Edition application is any deployable unit of Java EE functionality. This can be a single Java EE module or a group of modules packaged into an EAR file along with a Java EE application deployment descriptor. Java EE applications are typically engineered to be distributed across multiple computing tiers. Enterprise applications can consist of the following: EJB modules (packaged in JAR files); Web modules (packaged in WAR files);