ArcGIS Server Implementation in the Web ADF

In this topic

• ArcGIS Server APIs
• ArcGIS Server APIs in the Web ADF
• Value objects
• Proxy objects
• Using ArcGIS Server Proxy and Value objects in the Web ADF
• Working with the Web ADF Map control
• Managing server context

ArcGIS Server APIs

• ArcGIS Server ArcObjects API
• ArcGIS Server Simple Object Access Protocol (SOAP) API

ArcGIS Server APIs in the Web ADF

 

Value objects

Proxy objects

• ArcGIS Server Proxy and Value objects—Each ArcGIS Server service type maintains a separate and distinct WSDL that describes how to work with the service via SOAP. The Web service proxy works with the ArcGIS Server Web service in a stateless manner. It is up to the developer to manage state on the client, known as a shallowly stateful application. On the client, the ArcGIS Server Web service proxy manages SOAP serialization and deserialization for you. On the Web server, the ArcGIS Server Web service manages server context for you, via a .NET Hypertext Transfer Protocol (HTTP) handler or Java servlet. From the Web service perspective, all communication is stateless; therefore, it creates server context when processing an HTTP request and releases context when the HTTP response is sent to the client. 
  
  ArcGIS Server Value objects can be used with an ArcGIS Server server object, but the communication is more complex since COM proxies are now required. The WSDL does not define a DCOM proxy to work with a server object directly, as a result, the developer will need to manage the communication process. If a server object implements the IRequestHandler interface, use the HandleStringRequest method to send and receive SOAP requests and responses. The developer will be responsible for initiating the connection and serialization and deserialization SOAP. If Value objects are used, manage their serialization and deserialization. The Web ADF provides a DCOM proxy and set of supporting classes to do this. See the following illustration:
  
  

Using ArcGIS Server Proxy and Value objects in the Web ADF

Working with the Web ADF Map control

Managing server context

• Server context is released explicitly during the session—This option is not frequently used because server context is usually needed for the duration of the user session. Releasing context is a simple one line operation. The servercontext variable is a type of ESRI.ArcGIS.Server.IServerContext. See the following code example:

servercontext.ReleaseContext();

protected void Session_End(Object sender, EventArgs e)
{
    IServerContext context;
    for (int i = 0; i < Session.Count; i++)
    {
        context = Session[i] as IServerContext;
        if (context != null)
        {
            context.ReleaseContext();
        }
    }
    Session.RemoveAll();
}

• Server context is released when the Web browser is closed or the user navigates from the page—In ASP.NET 2.0, the callback framework can be leveraged to provide a more intuitive and performing solution for releasing server context. To implement this solution, handle the onunload event of the form on the Web page to generate a callback to the Web application. The callback iterates through the existing ArcGIS Server map resources and explicitly releases context for non-pooled services.

See Also: