Creating Complex Web Services

Now that you have completed the mandatory Hello World introduction to Web services, the next step is to get serious by developing a Web service that potentially could be used in a real-world application. The Web service in this case provides a LookUpCustomer webMethod that retrieves the customer information (Listing 9.2). This service, for instance, can be utilized by a Customer Relationship Management (CRM) application, pulling the customer information from a back-office Enterprise Resource Planning (ERP) application (see Figure 9.5).

Figure 9.5. XML data structure returned by the business Web service.

A couple of interesting features are highlighted next:

• Web services can be used to return both primitive types and complex types. In this scenario you have a custom data type represented by the Customer class, which is an aggregation of strings ( name , id) and a list of orders for that particular customer.

• Note the use of XmlAttribute and XmlElement serialization attributes attached with the properties of the Customer class. These are used by the .NET Framework to create a platform and a language “independent, XML-serialized representation of the Customer object.

• It uses SoapException to generate SOAP faults when the CustomerId input parameter is not specified.

Listing 9.2 Real-world Web Service

 <%@ Webservice class="hks.BusinessService" language="C#"%> using System; using System.Xml; using System.Xml.Serialization; using System.Web; using System.Web.Services; using System.Web.Services.Protocols; using System.Collections; namespace hks {    [WebService(Namespace="http://www.hiteshseth.com/WebServices")]    public class BusinessService    {       [WebMethod(Description="LookUp Customer, Complex Business Service")]       public Customer LookUpCustomer(String customerId) {         try         {          return Customer.LookUp(customerId);         }         catch (Exception Ex)         {          throw new SoapException(                              Ex.Message,SoapException.ClientFaultCode,"");         }       }    }    public class Customer    {       private String _name;       private String _id;       private ArrayList _orders;       public String Name       {          get          {             return _name;          }          set          {             _name = value;          }       }       [XmlAttribute("id")]       public String Id       {          get          {             return _id;          }          set          {             _id = value;          }       }       [XmlElement("Order",Type = typeof(Order))]       public ArrayList Orders       {          get          {             return _orders;          }          set          {             _orders = value;          }       }       public static Customer LookUp(String customerId) {          if (customerId==null  customerId.Equals(""))          {             throw new Exception("CustomerId Not Specified");          }          // Actual implementation will probably lookup from a database          Customer c = new Customer();          c.Id = customerId;          c.Name = "ABC Chemicals";          ArrayList orders = new ArrayList();          orders.Add(new Order(customerId,"ABC123",50));          orders.Add(new Order(customerId,"ABC456",100));          orders.Add(new Order(customerId,"ABC789",150));          c.Orders = orders;          return c;       }    }    public class Order {       public Order()       {}       private String _customerId;       public String CustomerId       {          get          {             return _customerId;          }          set          {             _customerId = value;          }       }       private String _item;       public String Item       {          get          {             return _item;          }          set          {             _item = value;          }       }       private int _price;       public int Price       {          get          {             return _price;          }          set          {             _price = value;          }       }       public Order(String customerId, String item, int price) {          _customerId = customerId;          _item = item;          _price = price;       }    } }