Codenotes for Web Services in Java and .Net - Softcover

Brill, Gregory

Softcover

ISBN 10: 0812966392 ISBN 13: 9780812966398

Verlag: Random House Inc, 2002

Inhaltsangabe

CodeNotes provides the most succinct, accurate, and speedy way for a developer to ramp up on a new technology or language. Unlike other programming books, CodeNotes drills down to the core aspects of a technology, focusing on the key elements needed in order to understand it quickly and implement it immediately. It is a unique resource for developers, filling the gap between comprehensive manuals and pocket references.

CodeNotes for Web Services in Java and .NET examines the core specifications and technologies required for building SOAP-based web services in both Java and .NET. Not only will you find descriptions of SOAP, WSDL, and UDDI; you will also see how to use each of these specifications with Java and .NET. In addition, you will find specific sections on cross-language and cross-platform compatibility between web services.
This edition of CodeNotes includes:

• A global overview of this technology and explanation of what problems it can be used to solve
• Real-world examples
• “How and Why” sections that provide hints, tricks, workarounds, and tips on what should be taken advantage of or avoided
• Instructions and classroom-style tutorials throughout from expert trainers and software developers

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Every CodeNotes title is written and reviewed by a team of commercial software developers and technology experts. See “About the Authors” at the front of the book for more information.

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Chapter 1

INTRODUCTION

What Are Web Services?

If you search the Internet, you will find an astounding variety of answers to the question "What is a web service?" The only common consensus is that web services share the following characteristics:

1. Web services use XML-based standards. As you will see in this book, web services are built on numerous APIs, standards, and protocols. Almost all of these systems use XML as a core component.

2. Web services use the Internet. In truth, most web services use standard Internet protocols, including HTTP and TCP/IP. However, web service technologies can also be deployed over messaging systems and other transport protocols.

3. Web services are platform- and language-neutral. You can build and deploy web services on almost any platform, using almost any language. Assuming you use the same version(s) of the same standard(s), a client developed in Java could easily use a web service developed in C# and hosted on Microsoft's Internet Information Services.

The next obvious question is "How can I use web services?" The answer to this question varies, depending on your specific need:

1. Linking legacy systems. If you work in a large corporation, you may want to take advantage of web services to provide cross-language and cross-platform compatibility. Why spend the time and money to rewrite your perfectly functional COBOL system in Java when you can develop a web service layer that allows your COBOL system to communicate with your new Java web portal?

2. Business to Business (B2B). The long-standing dream of simple, workable B2B communication can take a giant step forward with web services. Because web services work on open protocols, using XML you can develop B2B systems that actually work. No longer do you have to struggle with shared platforms or open large holes in your corporate firewall. Simply create straightforward web services that let your B2B partner build his own client using his own technology choices. Each side maintains control of the important pieces (technology choice, infrastructure, security, etc.), but both sides share a common, easy-to-understand set of services.

3. Service-based software. Web services open the door for many different types of service-based software. In the future, you may find small shell client programs that connect to a wide variety of web services on a subscription basis. The companies that host the web services can monitor your connections and charge you for each use. This approach may help prevent the ever-increasing bloat in common software packages.

A TYPICAL WEB SERVICE

A typical web service involves three distinct components. First, you need a contract that defines the service. Second, you need a producer, or host, for the service. Finally, you need a consumer, or client, to use, or consume, the service.

The Contract

The web service contract defines the name of the service, the service's input and output parameters, and how to communicate with the service. With some APIs the contract may also include information related to publication and discovery. In any case, the contract is always an XML document that follows a rigidly defined XML Schema (or dTD in some cases). The contract does not specify which software you have to use for either the server or client, nor does it specify security or transactional control.

The Producer

The producer generates the web service and hosts it. In most cases, the producer is a combination of a small-footprint web server with additional back end systems. The back end can be anything from a few simple stand-alone programs all the way up to enterprise systems using EJB. The real power of web services is that the contract isolates the producer from the client. The producer can use almost any back end system to host the service and provide the functionality, provided that the system can handle the appropriate web service standards.

The Consumer

The consumer, or client, finds the appropriate contract, connects to the producer, and uses the web service. In most cases, the client code is fairly simple and involves a few API calls. As with the producer, the consumer can use any technology that understands the web service API. The client program can be 100 percent pure Java even if the producer is using C# and IIS (or Apache and Perl for that matter).

The Roadmap

CodeNotes for Web Services is divided into seven chapters:

1. Introduction: The remainder of this chapter provides a short history of distributed computing and web services. We will also introduce you to the various standards, vendors, and technologies involved in building, promoting, and consuming web services. You may skip ahead to Chapter 3 if you want to see web services in action.

2. Installation: Throughout this book you will find web service examples built in a variety of languages and deployed on a variety of platforms, ranging from .NET and IIS, to Java and Apache. The installation chapter will show you the software and hardware requirements for building and supporting web services in each of these environments. Throughout this chapter you will find many CodeNotes pointers to more detailed installation instructions.

3. Simple Web Services: Chapter 3 consists of some simple web services built in various languages and implementations. This chapter is specifically designed to show you how easy web services are to build and to illustrate the basic web service framework. Once you have worked through this chapter, you will be better able to understand and appreciate the details of the various standards and systems in the remaining chapters.

4. SOAP and WSDL: The Simple Object Access Protocol, or SOAP, has emerged as a clear favorite among the various vendors pushing web services. SOAP is a pure XML-based standard for building and supporting web services. The Web Services Description Language, or WSDL, complements SOAP by providing a concise method for describing a web service. In this chapter, we will examine the details of both the SOAP and WSDL grammars.

5. Web Services in Java: In this chapter, we will take a detailed look at how web services can be developed using the Apache 2.2 SOAP API for Java. This chapter essentially builds on the examples in Chapter 3 and highlights the details specific to the Java implementation of SOAP and WSDL.

6. Web Services in .NET: In Chapter 6, we will look at how the .NET platform, and VS.NET in particular, can be used to build and use web services. This chapter also builds on the examples in Chapter 3 and highlights the details specific to web services in VB.NET and C#, built on VS.NET and IIS.

7. UDDI: The Universal Description, Discovery, and Integra-tion standard is both an XML-based directory service and a language-neutral specification for a web-based API to access the service. With regard to web services, the UDDI repository is the preferred place for storing WSDL documents and "publishing" your services to other businesses and the general public. In Chapter 7, we will examine the UDDI XML grammar, the API, and how you can use UDDI with web services.

In addition to these chapters, you can also find a short survey of several public web services at aWS010003.

Why Web Services: A History Lesson

Before you can understand why the concept of web services is so popular in computing literature, you must understand something of the history of distributed computing. In this section, we will take a quick look at the key technologies that have shaped distributed computing over the past ten years. These technologies and systems set the stage for web services and form the background against which web services will be measured.

DISTRIBUTED COMPUTING RPC,...

Details zur Ausgabe

• Verlag: Random House Inc
• Erscheinungsdatum: 2002
• Sprache: Englisch
• ISBN 10: 0812966392
• ISBN 13: 9780812966398
• Einband: Taschenbuch
• Anzahl der Seiten: 240
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar