Choosing a Web Services Provider

Before you begin developing your web service, you need to decide how you’re going host it. You have several choices: ASP.NET and .NET Remoting are the easiest ones to choose, and I’ll be focusing on ASP.NET in these examples, because it’s the option that gives you the most flexibility.

If you choose to serve your web services with ASP.NET, you need to be sure you have a web server capable of serving ASP.NET pages. IIS, the web server that ships with all Windows NT and Windows Server installations, will do just fine. However, if you’re running on Windows XP personal workstation, you don’t have a web server.Describing Web Services

Using the Cassini Personal Web Server

Although you could write your own ASP.NET host with the .NET Framework, Microsoft has developed a sample web server called Cassini, to demonstrate the .NET Framework’s web hosting capabilities. Cassini is written in C#, and comes with source code. You can download it from http://www.asp.net/Projects/Cassini/Download/.

After running cassini.exe to install Cassini, you can start it by double-clicking on the CassiniWebServer.exe icon. This will bring up the start screen shown in Figure 10-1.

You can enter the application directory (where your ASP.NET and HTML files are stored), the port the server will run on, and the virtual root (the path that URLs will be relative to) in the screen. Then click the Start button to start the server. Figure 10-2 shows some possible settings for the Cassini web server.

Alternately, you can start Cassini by typing the following command on the command line to start the server on port 80, mapping the URL http://localhost/dotNextAndXml/ to the directory named dotNetAndXml on your PC’s C drive:

CassiniWebServer C:dotNetAndXml 80 /dotNetAndXml

The Cassini web server will then start up and allow you to launch a web browser to the URL of the virtual root.

You can choose to run the web server on any port, as long as that port is not already being served by another TCP/IP server. Port 80 is the standard HTTP port, so if you have another web server running already, you might try running Cassini on port 8080 instead.

Now that you have the Cassini server running, you can launch a browser to see what’s being served. Click on the link titled “Click To Browse” to launch Internet Explorer and take a look around.

Cassini start screen
Figure 10-1. Cassini start screen
Cassini Web Server settings
Figure 10-2. Cassini Web Server settings

A web service is described with a WSDL file. The following elements are involved in a WSDL document:

definitions

This is the root element of a WSDL document.

types

This optional element can be used to define the data types which are used to describe the messages exchanged by this service.

message

This element is used to describe the messages exchanged by this service. The message element may have any number of part sub-elements, each of which can represent an individual parameter to the message. In general, there will be two message elements for each combination of method and transport; one for the request and one for the response.

portType

This element is used to define a set of abstract operations. An abstract operation represents a single round-trip query and response, and gives it a name which will be used in the binding element. In general, there will be one portType element for each transport.

binding

This element is used to connect an abstract operation to its message and transport. Transports can include SOAP, HTTP GET, and HTTP POST. In general, there will be one binding element for each transport.

service

This element is used to map each portType to its binding, including a URL used to access the service.

documentation

This element is used to contain additional, human-readable information about the service. It may appear anywhere in the WSDL document, has a mixed content model, and may contain any number of any other element (xs:any in XML Schema).

import

This element is used to allow a WSDL document to include the contents of another.

Now I’ll build a relatively simple WSDL document, which describes an inventory query service which I’ll introduce a little later. The XML prolog and document element are fairly uneventful, except for the large number of namespaces. The namespaces will be used for various purposes later in the document:

<?xml version="1.0" encoding="utf-8"?>
<definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" 
  xmlns:s="http://www.w3.org/2001/XMLSchema" 
  xmlns:s0="http://angushardware.com" 
  xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" 
  xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/" 
  xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" 
  targetNamespace="http://angushardware.com" 
  xmlns="http://schemas.xmlsoap.org/wsdl/">

The types element defines three elements using XML Schema: GetNumberInStock, GetNumberInStockResponse, and int. These elements will all be scoped in the target namespace, http://angushardware.com. The first two are complex types which define the parameters and return values of the messages, and the last one is equivalent to the predefined xs:int type:

<types>
  <s:schema elementFormDefault="qualified" 
     targetNamespace="http://angushardware.com">
    <s:element name="GetNumberInStock">
      <s:complexType>
        <s:sequence>
          <s:element minOccurs="0" maxOccurs="1" name="productCode" type="s:string" />
        </s:sequence>
      </s:complexType>
    </s:element>
    <s:element name="GetNumberInStockResponse">
      <s:complexType>
        <s:sequence>
          <s:element minOccurs="1" maxOccurs="1" name="GetNumberInStockResult" type="s:int" />
        </s:sequence>
      </s:complexType>
    </s:element>
    <s:element name="int" type="s:int" />
  </s:schema>
</types>

The two messages are defined here. GetNumberInStockSoapIn is a SOAP version of the GetNumberinStock request message, and GetNumberInStockSoapOut is a SOAP version of the GetNumberInStockResponse response message:

<message name="GetNumberInStockSoapIn">
  <part name="parameters" element="s0:GetNumberInStock" />
</message>
<message name="GetNumberInStockSoapOut">
  <part name="parameters" element="s0:GetNumberInStockResponse" />
</message>

This web service only supports a single operation, GetNumberInStock, so there is only one portType element. This element maps the GetNumberInStock operation to its SOAP input and output messages:

<portType name="InventoryQuerySoap">
  <operation name="GetNumberInStock">
    <input message="s0:GetNumberInStockSoapIn" />
    <output message="s0:GetNumberInStockSoapOut" />
  </operation>
</portType>

The binding element associates the InventoryQuerySoap portType with the SOAP transport, and defines the GetNumberInStock operation as a SOAP message:

<binding name="InventoryQuerySoap" type="s0:InventoryQuerySoap">
  <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document" />
  <operation name="GetNumberInStock">
    <soap:operation soapAction="http://angushardware.com/GetNumberInStock" style="document" />
    <input>
      <soap:body use="literal" />
    </input>
    <output>
      <soap:body use="literal" />
    </output>
  </operation>
</binding>

The service element describes the InventoryQuery service as being located at the URL http://127.0.0.1/dotNetAndXml/InventoryQuery.asmx, using the InventoryQuerySoap binding:

<service name="InventoryQuery">
  <port name="InventoryQuerySoap" binding="s0:InventoryQuerySoap">
    <soap:address location="http://127.0.0.1/dotNetAndXml/InventoryQuery.asmx" />
  </port>
</service>

Finally, as in all XML documents, the root element has to be closed:

</definitions>

That’s it, the InventoryQuery web service is now fully described.

Example 10-1 shows the complete WSDL document I built. It’s not a very complicated schema, but its contents can be confusing. Don’t worry, though; you’ll very rarely have to create it by hand. You’ll see in a moment how the .NET Framework creates one for you on demand.

Example 10-1. WSDL document for InventoryQuery service
<?xml version="1.0" encoding="utf-8"?>
<definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" 
xmlns:s="http://www.w3.org/2001/XMLSchema" 
xmlns:s0="http://angushardware.com" 
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" 
xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/" 
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" 
targetNamespace="http://angushardware.com" 
  xmlns="http://schemas.xmlsoap.org/wsdl/">
  <types>
    <s:schema elementFormDefault="qualified" targetNamespace="http://angushardware.com">
      <s:element name="GetNumberInStock">
        <s:complexType>
          <s:sequence>
            <s:element minOccurs="0" maxOccurs="1" name="productCode" type="s:string" />
          </s:sequence>
        </s:complexType>
      </s:element>
      <s:element name="GetNumberInStockResponse">
        <s:complexType>
          <s:sequence>
            <s:element minOccurs="1" maxOccurs="1" name="GetNumberInStockResult" 
             type="s:int" />
          </s:sequence>
        </s:complexType>
      </s:element>
      <s:element name="int" type="s:int" />
    </s:schema>
  </types>
  <message name="GetNumberInStockSoapIn">
    <part name="parameters" element="s0:GetNumberInStock" />
  </message>
  <message name="GetNumberInStockSoapOut">
    <part name="parameters" element="s0:GetNumberInStockResponse" />
  </message>
  <portType name="InventoryQuerySoap">
    <operation name="GetNumberInStock">
      <input message="s0:GetNumberInStockSoapIn" />
      <output message="s0:GetNumberInStockSoapOut" />
    </operation>
  </portType>
  <binding name="InventoryQuerySoap" type="s0:InventoryQuerySoap">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document" />
    <operation name="GetNumberInStock">
      <soap:operation soapAction="http://angushardware.com/GetNumberInStock" style="document" />
      <input>
        <soap:body use="literal" />
      </input>
      <output>
        <soap:body use="literal" />
      </output>
    </operation>
  </binding>
  <service name="InventoryQuery">
    <port name="InventoryQuerySoap" binding="s0:InventoryQuerySoap">
      <soap:address location="http://127.0.0.1/dotNetAndXml/InventoryQuery.asmx" />
    </port>
  </service>
</definitions>

Tip

The WSDL specification supported by .NET, currently at Version 1.1, is available at http://www.w3.org/TR/wsdl. It is technically a W3C Note, which means that it is only a submission to the W3C, and not an official recommendation or standard.

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
3.143.247.125