Getting started with the J2EE Web Service

Introduction
WSA is designed to work in concert with the j2's Configuration file. The j2's Configuration file is either based on the Connected Device Configuration (CDC) or the Connected Limited Device Configuration (CLDC 1.0 or CLDC 1.1 ). Remote Call API a complete subset of J2SE-Based Java API for XML-Based RPC (JAX-RPC 1.1) that contains some Remote Method Invocation (RMI) classes, to meet JAX-RPC dependencies. The XML parsing API is based on a complete subset of Simple API for XML and v2 (SAX2.
WSA aims to integrate basic support for Web service calling and XML parsing into the runtime environment of the device, in this way, developers do not have to embed such a feature in each application-it is a waste of resources in devices with limited resources such as mobile phones and personal digital assistants.
Core specifications
Web Services Interoperability Organization (WS-I) promotes core specifications and application layer protocols for defining Web Services, and they are subject to World Wide Web Consortium (W3C) and Organization for the Advancement of Structured Information Standards (OASIS) guidance. The four key criteria define how to create, deploy, discover, and use Web services:
Web service standard description
Simple Object Access Protocol (SOAP) 1.1 defines transmission and data encoding
Web Services Definition Language (WSDL) 1.1 defines how to describe remote Services
Universal Description, Discovery, & Integration (UDDI) 2.0 defines how to discover remote services
Extensible Markup Language (XML) 1.0 and XML Schema define Extensible Markup Language (XML) and XML Schema)
These main specifications are often very extensive, and Web Service developers have found it difficult to achieve full interoperability. To address the differences in the standard interpretation, the WS-I has defined a set of consistency rules called WS-I Basic Profile, version 1.0. JSR 172 complies with the Basic Profile ).
Web services on the j2-based Platform
JSR 172 specifies the standardized client technology that allows the use of remote services in a typical Web service architecture by the j2_application, as shown in Figure 1:
Figure 1 J2EE Web service in a typical Web Service Architecture
At the top, the Web service architecture has three elements:
A network-aware application that resides on a WSA wireless device. This application includes JSR 172 stubs that use the JSR 172 Runtime Library to communicate with the network. The role of the stub and the Runtime Library is described below.
Wireless networks and the Internet, as well as the corresponding communication and data encoding protocols, including binary, HTTP, and SOAP/XML.