Reading Notes：Enterprise JavaBeans, 3.0 Chapter 1. Introduction
Reading? Notes：Enterprise JavaBeans, 3.0 Chapter 1. Introduction
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1.1. Server-Side Components
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In business systems, object-oriented languages are used to improve development of GUIs, to simplify access to data, and to encapsulate the business logic.
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SOAP 1.1
Simple Object Access Protocol (SOAP) is an XML grammar, developed by Microsoft, IBM, and others, that is currently under the auspices of the W3C. It's an application protocol used in both RPC and asynchronous messaging. SOAP is very flexible and extensible and, unlike its predecessors (DCE RPC, CORBA IIOP, Java RMI-JRMP, and DCOM), it's been endorsed and adopted by just about every major vendor. (If you're not familiar with XML, see Java and XML or XML in a Nutshell, both from O'Reilly.)
WSDL 1.1
The Web Service Description Language (WSDL) is another XML grammar, developed by Microsoft and IBM under the auspices of the W3C. It is an XML-based Interface Definition Language (IDL) that can be used to describe web services, including the kind of message format expected, the Internet protocol used, and the Internet address of the web service.
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Web services are truly platform-independent. Although Java RMI and CORBA IIOP also claim to be platform-independent, in fact these older technologies require their own platforms.
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Web services, on the other hand, are not tied to a specific platform like the JVM or to a technology infrastructure like CORBA because they focus on the protocols used to exchange messages SOAP and WSDL and not on the implementation that supports those protocols. In other words, you can build web services on any platform using any programming language any way you please.
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EJB 3.0 allows enterprise beans to be exposed as web services so that their methods can be invoked by other J2EE applications as well as applications written in other programming languages on a variety of platforms. Web services in EJB 3.0 support both RPC-style and document-style messaging.
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