Enterprise JavaBeans, Fourth Edition

Chapter 18. XML Deployment Descriptors

This chapter teaches you how to write XML deployment descriptors for your beans. You may never need to write a deployment descriptor by hand: most vendors of integrated development tools and EJB servers provide tools for creating the descriptor automatically. Even if you have such a tool available, however, you must be familiar with deployment descriptors: the ability to read a deployment descriptor is an essential skill. This chapter does not attempt to teach you how to read or write correct XML. There are many books on the subject: XML Pocket Reference by Bob Eckstein (O’Reilly) is a good quick reference; XML in a Nutshell, by Elliotte Rusty Harold and W. Scott Means (O’Reilly), provides a more detailed treatment.

Very briefly, XML looks like HTML, but with different tag names and attributes inside the tags. You won’t see <h1> and <p> inside a deployment descriptor; instead, you’ll see tags like <ejb-jar>. But if you’re familiar with the structure of HTML, you’re most of the way towards reading XML. The tag names and attribute names for an XML document are defined by a special document called an XML Schema Definition (XSD). (EJB 2.0 used an older kind of definition document called a Document Type Definition (DTD)). An XSD or DTD defines the tags and attributes that can be used in a deployment descriptor, as well; the XSDs for deployment descriptors in EJB 2.1 and the DTDs for EJB 2.0 are available online at http://java.sun.com/xml/ns/j2ee/ejb-jar_2_1.xsd ...