Enterprise JavaBeans, Fourth Edition

The Document Headerand Schema Declarations

An XML document may start with a tag that specifies the version of XML in use:

<?xml version="1.0" encoding="UTF-8"?>

This tag identifies the document as an XML document that adheres to Version 1.0 of the XML specification and uses the UTF-8 character encoding. EJB vendors usually support this character encoding.

In EJB 2.1, the element following the XML header (the <ejb-jar> element) is the root element of the deployment descriptor. This element declares the document’s XML namespace and the location of the XML schema that can be used to validate its contents. A complete <ejb-jar> element looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar xmlns="http://java.sun.com/xml/ns/j2ee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
               http://java.sun.com/xml/ns/j2ee/ejb-jar_2_1.xsd"
      version="2.1">
...
</ejb-jar>

In EJB 2.0, a DOCTYPE element follows the document header and specifies the DTD that defines the document’s contents:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise
               JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
...
</ejb-jar>

In both EJB 2.1 and 2.0, the schema definition provides a URL from which you (or, more importantly, tools processing the deployment descriptor) can download the schema used to validate the XML document; this means that the EJB server deploying the bean can download the ...