Wednesday, November 28, 2007

Throwing custom Web Service Exception from Web Service

Suppose in a real scenario an exception is generated in the Data access or any other layer of our application and we want to show a custom message then we can use SoapException class in System.Web.Services.Protocols which will do the trick for us.

This is sample DAO class which has a method getEmpData which throws an exception

1    public class DAO
2 {
3 public DAO()
4 {
5 //
6 // TODO: Add constructor logic here
7 //

8 }
9
10 public static string getEmpData(int id)
11 {
12 throw new Exception("Method not supported");
13
14 }
15 }
The following is a sample Webservice with the webmethod in the same project which used the above DAO class
1    using System;
2 using System.Web;
3 using System.Web.Services;
4 using System.Web.Services.Protocols;
5
6 [WebService(Namespace = "http://tempuri.org/")]
7 [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
8 public class Service : System.Web.Services.WebService
9 {
10 public Service () {
11
12 //Uncomment the following line if using designed components
13 //InitializeComponent();

14 }
15
16 [WebMethod]
17 public string HelloWorld() {
18 try
19 {
20 return DAO.getEmpData(9);
21 }
22 catch (Exception ex)
23 {
24 throw new SoapException(ex.Message, SoapException.ServerFaultCode, Context.Request.Url.AbsoluteUri);
25 // return;
26 }
27 }
28
29 }
30

line 20 getEmpData pf the DAO class is called. The exception thrown is catched in the webmethod of the webservice in line 22, In this fasion you can bubble up the exception from any layer (even if it is a custom exception ) and handle that in the webmethod, it is better that you handle the soapException in webmethod, (if you want it to be present in any other class you will have to import System.Web.Services.Protocols namespace).

In this manner you can handle any Exception and pass the custom error messages to the client rather than the default error messages.

Some important properties of SoapException class (http://msdn2.microsoft.com/en-us/library/system.web.services.protocols.soapexception.aspx)

  • Message : The Message property of the original exception.
  • Code: ServerFaultCode.
  • Actor:The URL of the XML Web service method.
  • Detail:a null reference (Nothing in Visual Basic), but an empty detail element is present in the fault element.

After this i created a sample web application and called the Webmethod which throws the SoapException at line 2

     1  localhost.Service myser = new localhost.Service();
2 myser.HelloWorld();

Here at line 2 i got the custom error message passed from the DAO layer of the web service.
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