Introduction to Web Services.ppt

1、Introduction to Web Services,Yossi Amir Itzik Kasovitch,Agenda,Motivation History Web service model Web service components A walkthrough examples,Motivation,The ability to program the Web. Example: Consider an Excel spreadsheet that summarizes your whole financial picture : stocks, bank accounts, lo

2、ans, etc. If some of this information is available through XML Web services, Excel can update it and present the update information to the user.,Web Service definition,A simple definition:“a Web Service is an application component accessible over open protocols”.,History,Web services evolved from pr

3、evious technologies that served the same purpose such as RPC, ORPC (DCOM, CORBA and JAVA RMI). Web Services were intended to solve three main problems: Interoperability Firewall traversal Complexity,Interoperability,Earlier distributed systems suffered from interoperability issues because each vendo

4、r implemented its own on-wire format for distributed object messaging. Development of DCOM apps strictly bound to Windows Operating system. Development of RMI bound to Java programming language.,Firewall traversal,Collaboration across corporations was an issue because distributed systems such as COR

5、BA and DCOM used non-standard ports. Web Services use HTTP as a transport protocol and most of the firewalls allow access though port 80 (HTTP), leading to easier and dynamic collaboration.,Complexity,Web Services is a developer-friendly service system. Most of the above-mentioned technologies such

6、as RMI, COM, and CORBA involve a whole learning curve. New technologies and languages have to be learnt to implement these services.,Web Service definition revisited,A more precise definition: an application component that: Communicates via open protocols (HTTP, SMTP, etc.) Processes XML messages fr

7、amed using SOAP Describes its messages using XML Schema Provides an endpoint description using WSDL Can be discovered using UDDI,Web Services Components,XML eXtensible Markup Language A uniform data representation and exchange mechanism. SOAP Simple Object Access Protocol A standard way for communic

8、ation. UDDI Universal Description, Discovery and Integration specification A mechanism to register and locate WS based application. WSDL Web Services Description Language A standard meta language to described the services offered.,Example A simple Web Service,A buyer (which might be a simple client)

9、 is ordering goods from a seller service. The buyer finds the seller service by searching the UDDI directory. The seller service is a Web Service whose interface is defined using Web Services Description Language (WSDL). The buyer is invoking the order method on the seller service using Simple Objec

10、t Access Protocol (SOAP) and the WSDL definition for the seller service. The buyer knows what to expect in the SOAP reply message because this is defined in the WSDL definition for the seller service.,The Web Service Model,The Web Services architecture is based upon the interactions between three ro

11、les: Service provider Service registry Service requestor The interactions involve the: Publish operations Find operation Bind operations.,The Web Service Model (cont),The Web Services model follows the publish, find, and bind paradigm. 1. publish 2. find3. bind/invoke,Web Service Registry,Web Servic

12、e Provider,Web Service Client,XML,XML stands for EXtensible Markup Language. XML is a markup language much like HTML. XML was designed to describe data. XML tags are not predefined. You must define your own tags. The prefect choice for enabling cross-platform data communication in Web Services.,XML

13、vs HTML,An HTML example:,XML vs HTML,This will be displayed as:HTML specifies how the document is to be displayed, and not what information is contained in the document. Hard for machine to extract the embedded information. Relatively easy for human.,XML vs HTML,Now look at the following:In this cas

14、e: The information contained is being marked, but not for displaying. Readable by both human and machines.,SOAP,SOAP originally stood for “Simple Object Access Protocol“ . Web Services expose useful functionality to Web users through a standard Web protocol called SOAP. Soap is an XML vocabulary sta

15、ndard to enable programs on separate computers to interact across any network. SOAP is a simple markup language for describing messages between applications. Soap uses mainly HTTP as a transport protocol. That is, HTTP message contains a SOAP message as its payload section.,SOAP Characteristics,SOAP

16、 has three major characteristics: Extensibility security and WS-routing are among the extensions under development. Neutrality - SOAP can be used over any transport protocol such as HTTP, SMTP or even TCP. Independent - SOAP allows for any programming model .,SOAP Building Blocks,A SOAP message is a

17、n ordinary XML document containing the following elements: A required Envelope element that identifies the XML document as a SOAP message. An optional Header element that contains header information. A required Body element that contains call and response information. An optional Fault element that

18、provides information about errors that occurred while processing the message.,SOAP Request,SOAP Response,SOAP Security,SOAP uses HTTP as a transport protocol and hence can use HTTP security mainly HTTP over SSL. But, since SOAP can run over a number of application protocols (such as SMTP) security h

19、ad to be considered. The WS-Security specification defines a complete encryption system.,WSDL,WSDL stands for Web Services Description Language. WSDL is an XML vocabulary for describing Web services. It allows developers to describe Web Services and their capabilities, in a standard manner. WSDL spe

20、cifies what a request message must contain and what the response message will look like in unambiguous notation. In other words, it is a contract between the XML Web service and the client who wishes to use this service. In addition to describing message contents, WSDL defines where the service is a

21、vailable and what communications protocol is used to talk to the service.,The WSDL Document Structure,A WSDL document is just a simple XML document. It defines a web service using these major elements: port type - The operations performed by the web service. message - The messages used by the web se

22、rvice. types - The data types used by the web service. binding - The communication protocols used by the web service.,WSDL Document,UDDI,UDDI stands for Universal Description, Discovery and Integration. UDDI is a directory for storing information about web services , like yellow pages. UDDI is a dir

23、ectory of web service interfaces described by WSDL.,Resources,http:/ http:/ http:/ http:/ Many more on the web,Examples,Using a Web Service Creating a new Web Service,Step by Step using a web service,Inside Visual Studio .NET Choose File New Project. Choose Visual C# Projects (or Visual Basic Projec

24、ts if you prefer this language).,3. Choose ASP.NET Web Application as your template,Step by Step using a web service,Inside the Location text box enter the name of your project after the prefix :http:/localhost/YourProjectName Press OK. This makes The Internet Information Services installed on your

25、computer create a new directory on the default path: C:InetpubwwwrootFirstExample,Step by Step using a web service,You can open IIS by typing compmgmt.msc s in the run command and then choosing Services And Application Internet Information Services. Inside this node you can choose Web Sites node and

26、 then Default Web Site to see all the web sites on your computer.,Step by Step using a web service,Step by Step using a web service,In the new project you opened in VS.NET Move to the Solution Explorer. Right Click on the References folder and Choose Add Web References. This Opens the Add Web Refere

27、nce Dialog Box.,Step by Step using a web service,Type the Web Service URL and Press Go. It takes a couple of seconds to find the Web services and finally all its methods appear in the list box. The Web Reference name is shown in the Dialog Box. Press Add Reference to complete the process.,Step by St

28、ep using a web service,Step by Step using a web service,Add a new Web Form.,Step by Step using a web service,Add the following Controls to the Web Form,Step by Step using a web service,Double Click on the button and insert this code to its OnClick event handler.,Step by Step using a web service,Set

29、the Web Form as the Start Page. Build and Run the Program. Try to use the Web Application.,Step By Step Creating a Web Service,In this Step I will create a new Web Service and write a Simple Program that uses it. The program will perform various operations on an array. The client program will be a s

30、imple dialog box that activates those opeartions.,Step By Step Creating a Web Service,Create a new Visual C# project with the name RemoteArray. The following screen appears.,Step By Step Creating a Web Service,To see the code Press on the following hyperlink.,Step By Step Creating a Web Service,Righ

31、t Click on the References folder and choose add Reference. Insert the System.Windows.Forms.dll option in to this folder.,Step By Step Creating a Web Service,Step By Step Creating a Web Service,Step By Step Creating a Web Service,Insert the following code to the .asmx file youve created.,Step By Step

32、 Creating a Web Service,Step By Step Creating a Web Service,Step By Step Creating a Web Service,Press Ctrl +F5 to Run the Web service.,Step By Step Using Remote Array,Add a new project to RemoteArray Solution,Step By Step Using Remote Array,Choose Windows Application from the templates. Add a web re

33、ference for the Remote Array Web Service. Remember that its inside an asmx file.,Step By Step Using Remote Array,Step By Step Using Remote Array,Add the following elements to the Form,Step By Step Using Remote Array,Create a private RemoteArray object and a private int array object to the Form. Inse

34、rt this code after the Initialize component part.,Step By Step Using Remote Array,Insert the following code to controls handler,Step By Step Using Remote Array,Set the Windows Application project as the Startup,Step By Step Using Remote Array,Compile and run the application. This is an example that an XML Web application can be used over Windows and not only with ASP.NET,Introduction to Web Services,The End,