Chapter 12. JAX-WS Web Services

Java API for XML Web Services (JAX-WS) is an API included in the Java Enterprise Edition (EE) platform, and is used to create Web Services. Web Services are applications designed to communicate with each other over a network, typically exchanging information in XML or other structured text formats. Web Services are platform-independent. A typical JAX-WS application uses a client/server model. The server component is called a Web Service Endpoint.

JAX-WS has a counterpart for smaller and simpler Web Services, which use a protocol called JAX-RS. JAX-RS is a protocol for Representational State Transfer, or REST. JAX-RS applications are typically light-weight, and rely only on the HTTP protocol itself for communication. JAX-WS makes it easier to support various Web Service oriented protocols, such as WS-Notification, WS-Addressing, WS-Policy, WS-Security, and WS-Trust. They communicate using a specialized XML languaged called Simple Object Access Protocol (SOAP), which defines a message architecture and message formats.

A JAX-WS Web Services also includes a machine-readable description of the operations it provides, written in Web Services Description Language (WSDL), which is a specialized XML document type.

A Web Service Endpoint consists of a class which implements WebService and WebMethod interfaces.

A Web Service Client consists of a client which depends upon several classes called stubs, which are generated from the WSDL definition. JBoss Enterprise Application Platform includes the tools to generate the classes from WSDL.

In a JAX-WS Web service, a formal contract is established to describe the interface that the Web Service offers. The contract is typically written in WSDL, but may be written in SOAP messages. The architecture of the Web Service typically addresses business requirements, such as transactions, security, messaging, and coordination. JBoss Enterprise Application Platform provides mechanisms for handling these business concerns.

Web Services Description Language (WSDL) is an XML-based language used to describe Web Services and how to access them. The Web Service itself is written in Java or another programming language. The WSDL definition consists of references to the interface, port definitions, and instructions for how other Web Services should interact with it over a network. Web Services communicate with each other using Simple Object Access Protocol (SOAP). This type of Web Service contrasts with RESTful Web Services, built using Representative State Transfer (REST) design principles. These RESTful Web Services do not require the use of WSDL or SOAP, but rely on the structure of the HTTP protocol itself to define how other services interact with them.

JBoss Enterprise Application Platform includes support for deploying JAX-WS Web Service endpoints. This support is provided by JBossWS. Configuration of the Web Services subsystem, such as endpoint configuration, handler chains, and handlers, is provided through the webservices subsystem.