EJB J2EE and XML Web Services Expertise Developer s Guide to Building XML based Web Services with the Java 2 Platform Enterprise Edition J2EE By James Kao June 2001 Prepared for Sun Microsystems Inc Developer s Guide to Building XML based Web Services with the Java 2 Enterprise Edition 2001 The Middleware Company http www middleware company com Page 1 Table of Contents I Executive Summary 3 II Introduction 3 III Overview 3 IV Client Tier Connectivity 5 Business Partner Connectivity 6 Thin Client Connectivity 14 Thick Client Connectivity 15 V Implementing Web Services 15 Data Translation and Transformation 15 Shared Context 16 Business Layer 16 VI Performing Back End Integration 18 Database Connectivity 19 Legacy System Connectivity 19 Business Partner Connectivity 19 VIII Conclusion 21 Developer s Guide to Building XML based Web Services with the Java 2 Enterprise Edition 2001 The Middleware Company http www middleware company com Page 2 I Executive Summary Web services using XML standards is a new paradigm in the way B2B collaborations are modeled It provides a conceptual and architectural foundation which can be implemented using a variety of platforms and products Today developers can use the Java 2 Enterprise Edition J2EE to build XML based web services They can leverage existing J2EE technologies to build a complete and fully interoperable web service that complies with XML standards Without radical reengineering and without rebuilding a proven J2EE system developers can construct complex and powerful web services applications II Introduction A web service is an application that accepts requests from other systems across the Internet or an Intranet mediated by lightweight vendor neutral communications technologies These communications technologies allow any network enabled systems to interact As technologies mature a web service will encompass additional special functionality geared towards performing multiparty B2B collaboration Web services are evolving and beginning to operate in an extremely intelligent and dynamic way These smart web services will understand the context of each request and produce dynamic results based on each specific situation The services will adapt their processes based on the user s identity preferences location and reason for the request Multiple services will be combined on the fly collaborating to produce a unique customized solution The mechanics of this collaboration will be completely transparent to the consumer who will experience only the collective benefit delivered by the end result The XML standards which a web services system is built upon allows for an implementation neutral approach to performing business collaborations There are many possible implementations developers can use including a variety of products platforms and standards By using a standards based approach developers can build a system that provides maximum interoperability for their web services This white paper describes the portable Java and XML technology approach for implementing a web services architecture It explains each of the key web services technologies and how they fit together You will gain a better understanding of the concepts that underlie a XML web services architecture and how they fit together with J2EE We begin with a 30 000 foot birds eye view of how to build web services using J2EE This section will give you a high level understanding of the building blocks of a web services system We will elaborate on each functional area later in this white paper III Overview Traditionally there have been many barriers to two or more businesses collaborating in electronic transactions Widely disparate systems security issues and incompatible data formats have made largescale B2B integration the sole domain of large businesses and their large partners Web services will change the field of play and allow collaboration to occur between businesses of all sizes significantly reducing the development and maintenance costs of building business webs There are three major challenges in building a web service that participates in a business web 1 Build client tier connectivity to allow applets applications business partners web browsers and PDAs connect and make use of a web service 2 Implement the web service including any workflow logic data transformation logic business logic and data access logic This is the functionality behind the web service that performs work on behalf of the clients 3 Connect to back end systems which may include one or more databases existing enterprise information systems business partners that publish their own web services and a shared context repository for user information shared across many systems Developer s Guide to Building XML based Web Services with the Java 2 Enterprise Edition 2001 The Middleware Company http www middleware company com Page 3 You can achieve these three goals in building web services by using the Java 2 Platform Enterprise Edition J2EE While J2EE has historically been used to build traditional packaged applications userinterface driven deployments and other enterprise class systems it is also a viable web services platform The web services development model with J2EE relies on the following two standard technologies XML technologies The use of XML standards is very important in the overall scheme of the web services universe XML is a data format that represents data in a serialized form that can be transported over the network from one endpoint to another These various XML standards are primarily wire level protocols with a few exceptions along with specified processes designed to support a particular semantic behavior Java technologies Developers use J2EE APIs to author business and presentation logic access XML documents and perform XML operations Reliance on proven Java technology is important because it allows developers to leverage existing infrastructure to achieve a whole new level of functionality Developers continue to embrace the J2EE paradigm of using standard APIs with many possible implementations to create systems built from best of breed components Today developers have the APIs necessary to build a web service using J2EE A critical component of this is the Java API for XML Parsing JAXP which we will describe later The future will bring a few new JAX APIs mainly for dealing with the XML data formats and services These future JAX API s will allow for greater ease and speed in development Figure 1