dataportal.cs

C# 版本的一个三层商业架构

using System;
using System.Collections.Specialized;
using System.Reflection;
using System.Security.Principal;
using CSLA;
using CSLA.Resources;

namespace CSLA.Server
{
  /// <summary>
  /// Implements the server-side DataPortal as discussed
  /// in Chapter 5.
  /// </summary>
  public class DataPortal : MarshalByRefObject
  {

    #region Data Access

    /// <summary>
    /// Called by the client-side DataPortal to create a new object.
    /// </summary>
    /// <param name="Criteria">Object-specific criteria.</param>
    /// <param name="Principal">The user's principal object (if using CSLA .NET security).
    /// </param>
    /// <returns>A populated business object.</returns>
    public object Create(object criteria, DataPortalContext context)
    {
      object obj = null;

      try
      {
        SetContext(context);

        // create an instance of the business object
        obj = CreateBusinessObject(criteria);

        // tell the business object we're about to make a DataPortal_xyz call
        CallMethod(obj, "DataPortal_OnDataPortalInvoke", new DataPortalEventArgs(context));

        // tell the business object to fetch its data
        CallMethod(obj, "DataPortal_Create", criteria);

        // tell the business object the DataPortal_xyz call is complete
        CallMethod(obj, "DataPortal_OnDataPortalInvokeComplete", new DataPortalEventArgs(context));

        // return the populated business object as a result
        if(context.IsRemotePortal)
          Serialization.SerializationNotification.OnSerializing(obj);

        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        return result;
      }
      catch(Exception ex)
      {
        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        throw new DataPortalException("DataPortal.Create " + Strings.GetResourceString("FailedOnServer"), ex, result);
      }
    }

    /// <summary>
    /// Called by the client-side DataProtal to retrieve an object.
    /// </summary>
    /// <param name="Criteria">Object-specific criteria.</param>
    /// <param name="Principal">The user's principal object (if using CSLA .NET security).
    /// </param>
    /// <returns>A populated business object.</returns>
    public object Fetch(object criteria, DataPortalContext context)
    {
      object obj = null;

      try
      {
        SetContext(context);

        // create an instance of the business object
        obj = CreateBusinessObject(criteria);

        // tell the business object we're about to make a DataPortal_xyz call
        CallMethod(obj, "DataPortal_OnDataPortalInvoke", new DataPortalEventArgs(context));

        // tell the business object to fetch its data
        CallMethod(obj, "DataPortal_Fetch", criteria);

        // tell the business object the DataPortal_xyz call is complete
        CallMethod(obj, "DataPortal_OnDataPortalInvokeComplete", new DataPortalEventArgs(context));

        // return the populated business object as a result
        if(context.IsRemotePortal)
          Serialization.SerializationNotification.OnSerializing(obj);

        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        return result;
      }
      catch(Exception ex)
      {
        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        throw new DataPortalException("DataPortal.Fetch " + Strings.GetResourceString("FailedOnServer"), ex, result);
      }
    }

    /// <summary>
    /// Called by the client-side DataPortal to update an object.
    /// </summary>
    /// <param name="obj">A reference to the object being updated.</param>
    /// <param name="Principal">The user's principal object (if using CSLA .NET security).
    /// </param>
    /// <returns>A reference to the newly updated object.</returns>
    public object Update(object obj, DataPortalContext context)
    {
      try
      {
        SetContext(context);

        if(context.IsRemotePortal)
          Serialization.SerializationNotification.OnDeserialized(obj);

        // tell the business object we're about to make a DataPortal_xyz call
        CallMethod(obj, "DataPortal_OnDataPortalInvoke", new DataPortalEventArgs(context));

        // tell the business object to update itself
        CallMethod(obj, "DataPortal_Update");

        // tell the business object the DataPortal_xyz call is complete
        CallMethod(obj, "DataPortal_OnDataPortalInvokeComplete", new DataPortalEventArgs(context));

        if(context.IsRemotePortal)
          Serialization.SerializationNotification.OnSerializing(obj);

        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        return result;
      }
      catch(Exception ex)
      {
        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        throw new DataPortalException("DataPortal.Update " + Strings.GetResourceString("FailedOnServer"), ex, result);
      }
    }

    /// <summary>
    /// Called by the client-side DataPortal to delete an object.
    /// </summary>
    /// <param name="Criteria">Object-specific criteria.</param>
    /// <param name="Principal">The user's principal object (if using CSLA .NET security).
    /// </param>
    public object Delete(object criteria, DataPortalContext context)
    {
      object obj = null;

      try
      {
        SetContext(context);

        // create an instance of the business object
        obj = CreateBusinessObject(criteria);

        // tell the business object we're about to make a DataPortal_xyz call
        CallMethod(obj, "DataPortal_OnDataPortalInvoke", new DataPortalEventArgs(context));

        // tell the business object to fetch its data
        CallMethod(obj, "DataPortal_Delete", criteria);

        // tell the business object the DataPortal_xyz call is complete
        CallMethod(obj, "DataPortal_OnDataPortalInvokeComplete", new DataPortalEventArgs(context));

        // return the populated business object as a result
        if(context.IsRemotePortal)
          Serialization.SerializationNotification.OnSerializing(obj);

        DataPortalResult result = new DataPortalResult(obj);
        ClearContext(context);
        return result;
      }
      catch(Exception ex)
      {
        DataPortalResult result = new DataPortalResult();
        ClearContext(context);
        throw new DataPortalException("DataPortal.Delete " + Strings.GetResourceString("FailedOnServer"), ex, result);
      }
    }

    #endregion

    #region Security

    private string AUTHENTICATION
    {
      get
      {
        return ConfigurationSettings.AppSettings["Authentication"];
      }
    }

    private void SetContext(DataPortalContext context)
    {
      // if the dataportal is not remote then
      // do nothing
      if(!context.IsRemotePortal) 
        return;

      // set the app context to the value we got from
      // the client
      CSLA.ApplicationContext.SetContext(context.ClientContext, context.GlobalContext);

      if(AUTHENTICATION == "Windows")
      {
        // when using integrated security, Principal must be Nothing
        // and we need to set our policy to use the Windows principal
        if(context.Principal == null)
        {
          AppDomain.CurrentDomain.SetPrincipalPolicy(
            PrincipalPolicy.WindowsPrincipal);
          return;
        }
        else
          throw new System.Security.SecurityException(
            Strings.GetResourceString("NoPrincipalAllowedException"));
      }
      else
      {
        System.Diagnostics.Debug.Assert(AUTHENTICATION.Length > 0, 
          "No AUTHENTICATION token found in config file");
      }

      // we expect Principal to be of type BusinessPrincipal, but
      // we can't enforce that since it causes a circular reference
      // with the business library so instead we must use type object
      // for the parameter, so here we do a check on the type of the
      // parameter
      IPrincipal _principal = (IPrincipal)context.Principal;
      if(_principal != null)
      {
        IIdentity _identity = _principal.Identity;
        if(_identity != null)
        {
          if(_identity.AuthenticationType == "CSLA")
          {
            // See if our current principal is different from the caller's principal 
            if(!ReferenceEquals(context.Principal, System.Threading.Thread.CurrentPrincipal))
            {
              // The caller had a different principal, so change ours to match the 
              // caller's, so all our objects use the caller's security. 
              System.Threading.Thread.CurrentPrincipal = _principal;
            }
          }
          else
            throw new System.Security.SecurityException(
              Strings.GetResourceString("BusinessPrincipalException") + _principal.ToString());
        }
      }
      else
        throw new System.Security.SecurityException(
          Strings.GetResourceString("BusinessPrincipalException") + " null");
    }

    private void ClearContext(DataPortalContext context)
    {
      // if the dataportal is not remote then
      // do nothing
      if(!context.IsRemotePortal)
        return;

      ApplicationContext.Clear();
    }

    #endregion

    #region Creating the business object

    private object CreateBusinessObject(object criteria)
    {
      Type businessType;

      if(criteria.GetType().IsSubclassOf(typeof(CriteriaBase)))
      {
        // get the type of the actual business object
        // from CriteriaBase (using the new scheme)
        businessType = ((CriteriaBase)criteria).ObjectType;
      }
      else
      {
        // get the type of the actual business object
        // based on the nested class scheme in the book
        businessType = criteria.GetType().DeclaringType;
      }

      // create an instance of the business object
      return Activator.CreateInstance(businessType, true);
    }

    #endregion

    #region Calling a method

    object CallMethod(object obj, string method, params object[] p)
    {
      // call a private method on the object
      MethodInfo info = GetMethod(obj.GetType(), method);
      object result;

      try
      {
        result = info.Invoke(obj, p);
      }
      catch(System.Exception e)
      {
        throw new CallMethodException(info.Name + " method call failed", e.InnerException);
      }
      return result;
    }

    MethodInfo GetMethod(Type objectType, string method)
    {
      return objectType.GetMethod(method,
        BindingFlags.FlattenHierarchy |
        BindingFlags.Instance |
        BindingFlags.Public |
        BindingFlags.NonPublic);
    }

    #endregion

  }
}