What is WSIT?
Sun is working closely with Microsoft to ensure interoperability of web services enterprise technologies such as message optimization, reliable messaging, and security. The initial release of WSIT is a product of this joint effort. WSIT is an implementation of a number of open web services specifications to support enterprise features. In addition to message optimization, reliable messaging, and security,WSIT includes a bootstrapping and configuration technology. Figure 1–1 shows the underlying services that were implemented for each technology.

Starting with the core XML support currently built into the Java platform, WSIT uses or extends existing features and adds new support for interoperable web services. See the following sections for an overview of each feature:

• Bootstrapping and Configuration (page 3)
• Message Optimization Technology (page 4)
• Reliable Messaging Technology (page 5)
• Security Technology (page 6)

Java EE Application Model

The Java EE application model begins with the Java programming language and the Java virtual machine. The proven portability, security, and developer productivity they provide forms the basis of the application model. Java EE is designed to support applications that implement enterprise services for customers, employees, suppliers, partners, and others who make demands on or contributions to the enterprise. Such applications are inherently complex, potentially accessing data from a variety of sources and distributing applications to a variety of clients.

Distributed Multitiered Applications

The Java EE platform uses a distributed multitiered application model for enterprise applications. Application logic is divided into components according to function, and the various application components that make up a Java EE application are installed on different machines depending on the tier in the multitiered Java EE environment to which the application component belongs. Figure 1–1 shows two multitiered Java EE applications divided into the tiers described in the following list. The Java EE application parts shown in Figure 1–1 are presented in Java EE Components (page 4).

Building Web Services with JAX-WS

JAX-WS stands for Java API for XML Web Services. JAX-WS is a technology for building web services and clients that communicate using XML. JAX-WS allows developers to write message-oriented as well as RPC-oriented web services. In JAX-WS, a remote procedure call is represented by an XML-based protocol such as SOAP. The SOAP specification defines the envelope structure, encoding rules, and conventions for representing remote procedure calls and responses. These calls and responses are transmitted as SOAP messages (XML files) over HTTP.

Although SOAP messages are complex, the JAX-WS API hides this complexity from the application developer. On the server side, the developer specifies the remote procedures by defining methods in an interface written in the Java programming language. The developer also codes one or more classes that implement those methods. Client programs are also easy to code. A client creates a proxy (a local object representing the service) and then simply invokes methods on the proxy. With JAX-WS, the developer does not generate or parse SOAP messages. It is the JAX-WS runtime system that converts the API calls and responses to and from SOAP messages.