Introduccion web services

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Introduction

THE realm of Web services—software components that are programmatically
accessible over standard Internet protocols—is expanding rapidly due to the growing need for application-to-application communication and interoperability. Web services expose a standard interface that is platform and technology independent. By conforming to accepted industry-widestandards, Web services provide a means of communication among software applications running on different platforms and written in different application development languages and that present dynamic context-driven information to the user. Since its successful introduction in 1999, the J2EE platform has become an integrated standard for implementing and deploying portable and distributed enterpriseapplications. One significant factor contributing to this success is that the J2EE platform has been designed through an open process, the Java Community Process (JCP). This open process has engaged a range of enterprise computing vendors to ensure that the platform meets the widest possible spectrum of enterprise application requirements. As a result, the J2EE platform addresses the core issues thatimpede organizations’ efforts to maintain a competitive pace in the information economy. Organizations have recognized this and quickly adopted the J2EE platform standard. The J2EE platform has evolved further to accommodate the growing popularity and use of Web services. The platform has added support for Web servicespecific components and technologies. The Web services standards ensureinteroperability across platforms and programming languages. Also portability— the ability to migrate applications from one platform to another—is just as important. Significantly, the J2EE platform adds portability to Web services. By combining portability and interoperability, the J2EE platform is a compelling platform
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for developing distributed systems. These new J2EE components andtechnologies meet the requirements of most enterprises: These technologies allow enterprises to expose their existing applications as Web services and to develop and implement new Web services. This Web-service evolution of the J2EE platform has been achieved with the same open process as before involving leading enterprise computing vendors. It has ensured that the J2EE platform is the platform of choicefor developing and deploying portable and interoperable Web services and enterprise applications. Let’s look at some of the reasons why this is so. The J2EE platform has added its Web services features to a platform that has already standardized development and deployment of portable enterprise applications. With these new features, the J2EE platform offers enterprises the following benefits: •Enables existing enterprise applications to be extended as Web services in a manner that is standard, easy, portable, and interoperable • Helps extend the reach of existing and new enterprise applications to a new set of clients beyond the already wide variety of clients supported by the earlier J2EE platforms • Enables using commercially proven, robust technologies (such as enterprise beancomponents, servlets, and so forth) as the backbone for developing new services • Helps existing enterprise information systems (EISs) to be integrated to end users in a portable way This book is about developing robust, effective Web services on the JavaTM 2 Platform, Enterprise Edition (J2EETM), version 1.4 or later. The book not only describes the technologies used for Web services, but also presentsguidelines for using these technologies to design and develop Web services. Many of these guidelines have been formulated from our own Web service development experience, and, as such, we have illustrated the guidelines with real examples when possible. This first chapter sets the groundwork for the book—it gives you a look at some of the key concepts underlying the architectural details of Web...