การสร างเว บเซอร ว สโดยใช Microsoft.NET

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Britney Horton
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1 การสร างเว บเซอร ว สโดยใช Microsoft.NET อ.ดร. กานดา ร ณนะพงศา ภาคว ชาว ศวกรรมคอมพ วเตอร คณะว ศวกรรมคอมพ วเตอร มหาว ทยาล ยขอนแก น บทน า.NET เป นเคร องม อท เราสามารถน ามาใช ในการสร างและเร ยกเว บเซอร ว สได โดยง าย ข อด ของ.NET ม หลายประการอย างเช น ใช ง าย สามารถน ามาสร างเว บเซอร ว สท งแบบ RPC style และ document style โดยท document style จะเป น default style ของเว บเซอร ว สท.NET สร างข น ผ ท เร ยกเว บ เซอร ว สท.NET สร างสามารถท จะเร ยก.NET ในแบบ synchronous style หร อ asynchronous style ซ งถ าเป นแบบ asynchronous style ผ เร ยกใช เซอร ว สก สามารถจะท างานอ นได ในขณะรอผลของเว บเซอร ว ส ท เร ยกไป The.NET Web Service Architecture Microsoft s implementation of web service is designed to make it just as easy to invoke a remote web service as to call a method on a local class. To achieve this, the.net Framework provides tools that hide the often-tedious details of standards like SOAP and WSDL. The process works like this (note that the steps in italic steps 1, 3, 5, and 8 are the only steps that are performed manually): 1. You design a web service as a.net class with attributes that identify it as a web service with exposed functions 2..NET automatically creates a WSDL document that describes how a client must communicate with the web service 3. A client finds your web service and decides to use it. The client adds it as a web reference to a Visual Studio.NET project (or runs the WSDL.exe utility) 4..NET automatically inspects the WSDL document and generates a proxy class that allows the client to communicate with the web service transparently 5. The client calls one of the methods of your web service class. From the client s perspective, it seems no different that calling a method in any other class, but in reality, the client is interacting with the proxy class, not the web service 6. Behind the scenes, the proxy class converts the supplied parameters to a SOAP message and sends it to the web service 7. A short time later, the proxy class receives a SOAP reply, converts it to the appropriate data type, and returns it to the client as an ordinary.net data type 8. The client uses the returned information 1

Creating Hello, World with Visual Studio.NET To create a new web service, fire up Visual Studio.NET and click File New Project on the main Visual Studio.NET menu bar.

2 Creating Hello, World with Visual Studio.NET To create a new web service, fire up Visual Studio.NET and click File New Project on the main Visual Studio.NET menu bar. Then, there should be New Project window pop up. Then, you choose ASP.NET Web Service After selecting this option to create a new project, you ll see the screen in Figure 1. Figure 1: Creating a new Visual Studio project Exploring the solution and project The contents of your new project are displayed in the Solution Explorer window which should appear on the right side of the VS.NET IDE, as shown in Figure 2. 2

Figure 2: The Visual Studio.NET Solution Explorer If the Solution Explorer is not visible, you can open it by selecting Solution Explorer from the View menu. VS.

3 Figure 2: The Visual Studio.NET Solution Explorer If the Solution Explorer is not visible, you can open it by selecting Solution Explorer from the View menu. VS.NET also automatically creates several assembly references and files, which are also displayed in the Solution Explorer, as shown in Figure 2. In this example, VS.NET has included System, System.Data, System.Web, System.Web.Services, and System.XML namespaces The four other files that appear in Figure 2 are AssemblyInfo.cs, Global.asax, Service1.asmx and Web.config AssemblyInfo.cs An information file that provides the compiler with metadata (name, version, etc.) about the assemblies in the project Global.asax Customizable to handle application-level events (e.g., application_onstart). Web.config An XML file containing configuration information for the application Exploring the.asmx file and service design view The most important file in our example is the sample service page named Service1.asmx. If you open the page by double-cliing it, VS.NET displays a blank design page in its main window. You can view the source code of your service by right-clicking on the Service1.asmx file in Solution Explorer and selecting View 3

4 Code. At this point, you ll also want to rename the Service1.asmx file to something more appropriate to the project. You can do this by right-clicking the file in Solution Explorer and selecting Rename from the menu. Change the name to the HelloService.asmx You should uncomment the codes in the HelloWorld(). The contents of the source file HelloWorld.asmx.cs should be similar to that produced in Figure 3. Figure 3: VS.NET HelloWorldService codes Testing the Service If you open a browser and type in the URL You ll see the IE test page as shown in Figure 4. 4

5 Figure4: HelloWorldService page Then you click HelloWorld. Then you should see the page as shown in Figure 4. Then, you should go to the will see the page as shown in Figure 5. Figure 5: HelloWorldService Test Page 5

6 Invoking the Web Method You can invoke the web method using the ID by opening a web browser and navigating to the service s URL. You will see a page listing the service s operation, by clicking a button labeled Invoke In voking the example service provides the results shown in Figure 6. Figure 6: HelloWorldService output You know that web services are a means of commuting between servers using XMl, so it should come as no surprise that the output of our service nothing more than an XML document. The WebService Attribute One of the features missing from our HelloWorld web service is information about what it does. To tell a client about the functionality by our service, we need some mechanisms for documenting it..net provides System.Web.Services.WebServiceAttribute which you can use to let clients know where to find information about a web service. The WebService attribute has two properties: Namespace Sets the XML namespace for the service Description Adds a text/html description of the service that becomes part of the service description (WSDL document) In another example, we will use the Namespace and Description properties of the WebService attribute to document a web service named DNSLookupService, which takes a hostname as a string argument and uses a class called Dns from the System.Net namespaces to resolve and return the associated IP address. 6

Listing1. DNS LookupService Codes using System; using System.Collections; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Web; using System.Web.Services; using System.

7 Listing1. DNS LookupService Codes using System; using System.Collections; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Web; using System.Web.Services; using System.Net; namespace DNSLookupService [WebService(Namespace=" Description="<b>A web service which performs Domain Name Lookups.</b>")] public class DNSLookupService : System.Web.Services.WebService [WebMethod] public string getipforhostname(string strhostname) IPHostEntry hostinfo = Dns.GetHostByName(strHostname); return hostinfo.addresslist[0].tostring(); As you can see, HTML tags are permitted in the service description, making the resulting IE test page appear as shown in Figure 7. Figure 7: Adding a service description 7

8 Consuming Web Services The.NET web service consumer model makes use of client proxies,.net types that encapsulate for a client the process of making SOAP calls to the web service. A proxy class for a given service is typically created from its WSDL document. Once that proxy class has been created, all you need to do is reference it in your project as your would any other assembly or COM object. All calls to the web service are then handled through an instance of the proxy object, which takes are of the SOAP conversation with the server. The process is shown in Figure 8. Figure 8: Calling a web service through a proxy class The process shown in Figure 8 begins when the consumer application on the client instantiates an instance of the proxy object and performs method calls, passing it native.net types and classes as it would with any other class. The proxy object then converts the native.net type to an XML format and performs the remote method call to the web method on the server using SOAP. The SOAP message is transmitted over HTTP, received by the web server, and then dispatched to the appropriate ASP.Net web service. The web service then converts the SOAP message into a native type, performs the necessary processing, and returns the results to the proxy, again converted into an XML/SOAP format. The proxy deserializes the SOAP message to a.net type and 8

9 returns this type as the result of the initial method call. By operating in this fashion, the proxy DLL hides all of the implementation details of the underlying calls. The process described here is idealized to some extent because it assumes that there are no interoperability issues between the client and server. In reality, this is often not the case, because different SOAP implementations such as Apache Axis and SOAP::Lite have minor differences in the way they implement the SOAP specification. In some cases, this has led to interoperability problems between different implementations Creating a Client Proxy VS.NET makes the process of accessing a web service easy. Web service access is done through a proxy stub that is automatically created for you by the Add Web Reference feature of the VS.NET IDE. Add Web Reference feature. This automation makes working with web services through proxies as straightforward as working with other local assemblies Using VS.NET To illustrate proxy creation, let s create a new project in VS.NET. For this example, we ll use the C# Console Application template to create a new project that makes use of our DNSLookupService. VS.NET automatically includes the skeleton code and references necessary to compile a basic console application. You can add web reference by right click the project name and then choose Add Web Reference. Then choose the service that you want to use. If you can add web reference successfully, you should see the solution explorer as shown in Figure 9. Figure 9: The web reference in the Solution Explorer 9

Now that reference has been added, we have access to it in our code as we would any other local assembly or COM object. Listing2 uses DNSLookupService to look up IP addresses for hostnames.

10 Now that reference has been added, we have access to it in our code as we would any other local assembly or COM object. Listing2 uses DNSLookupService to look up IP addresses for hostnames. Listing2 DNSConsumerApp Codes using System; namespace DNSConsumerApp class Consumer [STAThread] static void Main(string[] args) localhost.dnslookupservice objdns = new localhost.dnslookupservice(); string stripaddress = ""; stripaddress = objdns.getipforhostname(args[0]); Console.WriteLine("Hostname: " + args[0] + " IP Address: " + stripaddress); You can compile DNSConsumerApp and run it from the command line by typing: DNSConsumerApp campus.en.kku.ac.th Figure 10 displays its output. Reference: Alex Ferranra and Matthew MacDonald, Programming.NET Web Servcies, O REILLY,

The contents of this document are directly taken from the EPiServer SDK. Please see the SDK for further technical information about EPiServer.

Web Services Product version: 4.50 Document version: 1.0 Document creation date: 04-05-2005 Purpose The contents of this document are directly taken from the EPiServer SDK. Please see the SDK for further