| A striking feature of J2EE is that Sun has done a wonderful job of providing middleware services that are part of the standard platform, but at the same time, it has left room for third-party middleware vendors to add value. These middleware services include transactional and messaging middleware services and distributed object services, all in support of Java-enabled distributed application development. The J2EE platform is made up of the J2EE deployment specification, a set of Internet Engineering Task Force (IETF) standards, and a set of CORBA standards. The middleware built into J2EE includes EJB, Java IDL, JDBC, JMS, Java Transaction API (JTA), Java Transaction Service (JTS), and RMI-IIOP. Although each of these middleware mechanisms is important, the most critical features are contained in the transactional component middleware, where EJB adds the most value; in JMS, which provides asynchronous messaging capabilities; and in RMI-IIOP, which provides synchronous object-to-object method sharing. XML and Java J2EE provides support for XML through the Java API for XML Processing (JAXP), which provides the ability to verify, create, access, and manipulate XML documents from Java applications. To manipulate an XML document, the document must first be parsed, validated, and made available through an API, including Document Object Model (DOM) and Simple API for XML (SAX). JAXP supports both APIs. Moreover, the ability to use XSLT framework (see Chapter 11) on the Transformation API for XML (TrAX) is also included in JAXP. Of course, Java and XML are always evolving, and Sun's Java Community program continues to define many XML-related specifications, including: The Java API for XML Messaging (JAXM) enables developers to send and receive XML messages based on the Simple Object Access Protocol (SOAP) with an attachments specification, and contains profiles for ebXML and SOAP-RP. The Java API for XML Processing enables developers to process XML documents by providing support for the XML processing standards SAX, DOM, and XSLT. The Java API for XML Registries (JAXR) provides a uniform and standard Java API for interacting with XML registries such as UDDI and ebXML Registry/Repository. The Java API for XML-based RPC (JAX-RPC) enables Java technology developers to build Web applications and Web services that incorporate XML-based RPC functionality according to the SOAP 1.1 specification. By using JAX-RPC, Java developers can rapidly achieve Web services interoperability based on widely adopted standards and protocols.[1]
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[1] Java XML Pack.
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