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Learn to teach you the basis of XML Web Service

Print View , by: iSee ,Total views: 6 ,Word Count: 2331 ,Date: Mon, 20 Apr 2009 Time: 2:33 AM


What is xml Web Service?

xml Web Service is a distributed computing on the Internet's basic building block. Open standards, as well as to users and applications of communication and collaboration between the concerns gave rise to such an environment, in this environment, xml Web Service as a platform for application integration. Applications through the use of a number of different sources of XML Web Service from the structure, these services will work together, regardless of where they are located or how to achieve it.

The number of XML Web Service to build the company, how many might have been the definition of XML Web Service. However, the definition of almost all have in common the following:

1. XML Web Service via a standard Web protocol to the Web user to provide useful functions. In most cases using the SOAP protocol.

2. XML Web Service can be very detailed description of its interface, which allows users to create a client application to communicate with them. This description is usually included in the referred to as Web Service Description Language (WSDL) document the XML document.

3. XML Web Service has been registered, so potential users can easily find these services, it is found through the universal, description, and Integration (UDDI) to complete.

XML Web Service architecture, one of the main advantages are: to allow different platforms in different languages to a variety of procedures, standards-based way to communicate with each other. Understanding of the industry once the user may say: "Wait a moment, CORBA and DCE before did not have the same commitment? This is What is the difference between them?" The most important difference is that: SOAP than before The method is much simpler, and therefore compatible with standard SOAP, but also much smaller obstacles. The last statistics, the list has already included 79. As you predicted, the majority of large software companies to achieve the provision of SOAP, but there are many realization of the program are set by individual developers to create and maintain. Program in terms of the relative before, XML Web Service, another major advantage of using the standard Web protocol - XML, HTTP and TCP / IP. Many companies have already established Web infrastructure, while safeguarding their employees also have the appropriate knowledge and experience. Therefore, the introduction of XML Web Service with the introduction of the previous technology, the cost is much lower.

XML Web Service we will be defined as: the adoption of SOAP in Web services provided by the software, use the WSDL description file, and UDDI to register. In that case, you may want to ask: "Using XML Web Service can do?" The first XML Web Service is usually can be easily incorporated into the source of information for applications, such as stock prices, weather forecasts, sports results and so on. We can easily think of, you can build an entire category of applications to the analysis and summary information of concern, and provide this information in various ways; for example, you can use Microsoft? Excel spreadsheets to aggregate financial information of all - the stock, 401K bank deposits, loans and so on. If the XML Web Service can access this information, Excel will be able to update continuously. Some of this information is free of charge, while others may require subscriptions to access the corresponding services. Most of this information can now be found on the Web, but XML Web Service allows access to programming more simple and more reliable.

XML Web Service to provide existing applications, you can build a new, more powerful applications and use XML Web Service as a building block. For example, users can develop a purchasing application to automatically access from the prices of different suppliers of information, so that users can choose the supplier, to submit orders, and then tracking the transport of goods until the receipt of the goods. And application providers in addition to provide Web services, can also use the XML Web Service to check customer's credit, collection of payment, and shipping companies and cargo clearance.

The future, some of the most interesting the support of XML Web Service applications can also use the Web to complete the current task can not be completed. For example, the calendar service is Microsoft. NET My Services project is about to support one of the services. If your dentist and mechanics through the XML Web Service to provide its schedule, you can network with their appointments; If you'd like, they can also directly in the calendar on your day-to-day cleaning and maintenance of the agreed date. It is not difficult to imagine, as long as they can on the Web program, you can create hundreds of applications.

SOAP

Soap is the XML Web Service communication protocol. When SOAP is described as a communication protocol, the majority of people will think of DCOM or CORBA, and would have asked "SOAP how to activate the object?" Or "SOAP namespace to use what kind of service?" And so on. Although the SOAP program could be included to achieve the above-mentioned content, but not their SOAP standard provisions. SOAP a standard for the definition of the XML message format - it is necessary to regulate in part. Included in a SOAP element and the structure of the XML above is correct SOAP message. This is not very simple?

Other parts of the SOAP specification describes how to process the data expressed as XML, and how to use SOAP for Remote Procedure Call (RPC). Some of these options for the realization of the normative form of RPC applications, which will issue the client a SOAP message (including callable function, and the need to send parameters to the function), and then the server will return the results contain information function. At present, the majority of the realization of the program SOAP support RPC applications, which is used as the development of COM or CORBA application programmers are familiar with the form of RPC. SOAP also supports document application forms, in such applications, SOAP message is an XML document packaging. SOAP document application form is very flexible, many new XML Web Service will use to build this feature difficult to use RPC services.

Finally SOAP specification defines an optional part of the HTTP message contains the SOAP message style. This HTTP binding is important because almost all the current os (and many of the previous OS) support HTTP. Although the HTTP binding is optional, but almost all SOAP support the realization of the program HTTP binding, because it is the only standard protocol SOAP. For this reason, people often mistakenly believe that SOAP must use HTTP. In fact, some programs also support the achievement of MSMQ, MQ Series, SMTP, or TCP / IP transmission, but because HTTP is very common, almost all current XML Web Service will use it. Since the HTTP protocol is the Web's core, most organizations are in support of network infrastructure, HTTP, and employees already know how to manage it. Now, has been established for the HTTP security, surveillance, and load-balancing infrastructure.

Start using SOAP, the most likely to confuse the SOAP specification and the many differences between the achievement of the program. Most users do not use SOAP to prepare SOAP messages directly but use the SOAP toolkit to create and analysis of SOAP messages. These kits usually function call from a language into a SOAP message. For example, Microsoft SOAP Toolkit 2.0 to COM function call is converted to SOAP, and Apache Toolkit to java function call is converted to SOAP. The type of function call parameters and support data types with each realization of the program SOAP vary, it is applied to the function of a tool kit may not be applicable to other tool kits. This is not the limit SOAP, but by the use of specific restrictions on the realization of the program.

So far, SOAP features of the most eye-catching is that it can be in many different software and hardware platforms. This means that SOAP can be used to link internal and external Enterprise systems. The past has tried to put forward a number of ways of system integration can be used for general-purpose communication protocol, but they are not the same as the SOAP widely recognized. Why? Because compared to many of our earlier agreement, SOAP is more compact and easier to achieve. For example, DCE and CORBA's a period of several years to achieve, it released only a few programs to achieve. SOAP can use the existing XML parser and HTTP libraries to complete the majority of hard work, so the realization of the program SOAP in a few months to complete. That is why now more than 70 SOAP reasons for the achievement of the program. Of course, SOAP does not have the DCE or all of the features of CORBA, although the function of reduction, but because of its greatly reduced complexity and therefore more easily applied SOAP.

The popularity of HTTP and SOAP and so simple you can almost call them from any environment, XML Web Service has therefore become the basis of the ideal.

How secure?

Typically, the usersSOAP first SOAP issue is how to solve the security issues. In its early stages of development, SOAP was seen as the agreement is based on HTTP, so that the security of HTTP for SOAP enough. After all, there are thousands of Web applications security in the use of HTTP, so it really has been enough for SOAP. Therefore, the assumption that the current SOAP security standards are transmission problems, and not as a security issue.

When extended to a more generic SOAP protocol, and run on the large number of transmission, the security issue becomes highlighted. For example, HTTP provides a number of ways to SOAP calls to authenticate users, but when routing messages from HTTP to SMTP transmission, how does the spread of the identity? SOAP protocol as a building block design, so it is fortunate , has been the norm for SOAP-based Web services to provide additional security protection. WS-Security specification (in English) the definition of a complete set of encryption systems, and WS-License specification (in English) the definition of the corresponding technology, in order to guarantee the identity of the caller ID, and to ensure that only authorized users can use Web services.

WSDL

WSDL (Web Services Description Language) that the Web Service Description Language. In this paper, we consider that the WSDL file is a XML document, used to describe a set of SOAP message and how to exchange these messages. In other words, WSDL for SOAP role of IDL as CORBA or COM for the role. WSDL is the XML document as a result, it is easy to read and edit; but the majority of cases, it is generated by the software and use.

To view the WSDL of the value, can be assumed that you want to call from your business partners to provide a method of SOAP. You can ask to provide some examples of SOAP messages, and then prepare your application to generate and use information and examples of similar, but it is very prone to error. For example, you may see a 2837 customer ID, and assuming that it is an integer, whereas actually it is a string. WSDL through the clear message that the law specified the request must contain the content and style in response to the news.

WSDL document used to describe the message format of the representation to the standard XML-based architecture, which means that it has nothing to do with the programming language, and standards-based, so that can be applied to different platforms, different programming languages to access the XML Web Service interface. In addition to the contents of that message, WSDL also defines the location of services, as well as the communication protocol used to communicate with the service. In other words, WSDL document defines the use of XML Web Service to prepare the entire contents of the required procedures. There are several tools can read the WSDL file and generate XML Web Service with the necessary communication code. Some of the most powerful tools available in Microsoft Visual Studio?. NET found.

At present, many SOAP toolkits include programming interfaces from the existing tools to generate WSDL documents


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