WROX - C# Web Services - Building Web Services with ASP.NET and.NET Remoting.pdf - ASP.NET - pawellop2m

Programmer to Programmer TM

Building Web Services with

.NET Remoting and ASP.NET

Ashish Banerjee, Aravind Corera, Zach Greenvoss, Andrew Krowczyk,

Christian Nagel, Chris Peiris, Thiru Thangarathinam, Brad Maiani

Web Services

Summary of Contents

Introduction

Section One – Getting Started

Chapter 1: What is a Web Service?

Chapter 2: Web Service Protocols

Chapter 3: Web Services and the .NET Framework

Section Two – ASP.NET Web Services

Chapter 4: Building an ASP.NET Web Service

Chapter 5: Consuming ASP.NET Web Services

105

Section Three – .NET Remoting

129

Chapter 6: .NET Remoting Architecture

131

Chapter 7: Web Services Anywhere

175

Chapter 8: Building a Web Service with .NET Remoting

201

Chapter 9: Building a .NET Remoting Client

231

Section Four – Advanced Topics

253

Chapter 10: Universal Description, Discovery and Integration (UDDI)

255

Chapter 11: .NET Security and Cryptography

275

Chapter 12: Web Services As Application Plug-Ins

333

Section Five – Case Studies

367

Case Study 1: ASP.NET

369

Case Study 2: P2P .NET Remoting

423

Section Six –Appendix

493

Appendix A: .NET Remoting Object Model

495

Index

581

.NET Remoting Architecture

In the last few chapters, we have seen how ASP.NET web services can be created and used. ASP.NET

web services require the ASP.NET runtime as hosting environment. Using .NET Remoting directly, we

can host a web service in any application we want. .NET Remoting allows much more flexibility

because different transport protocols may be used, we can get a performance increase with different

formatting options, and it's possible to host the server in different application types.

The next four chapters will deal with .NET Remoting. In this chapter, we will look at the architecture of

.NET Remoting, and go into detail in the following areas:

❑

What is .NET Remoting?

❑

.NET Remoting Fundamentals

❑

Object Types

❑

Activation

❑

Marshaling

❑

Asynchronous Remoting

❑

Call Contexts

The next chapter will show different application types, transport protocols, and formatting options, and

Chapters 8 and 9 will show an example of using .NET Remoting. Let's begin the chapter with a look at

.NET Remoting.

As with the previous chapters, the code for the examples in this chapter can be downloaded from

http://www.wrox.com .

Chapter 6

What is .NET Remoting?

.NET Remoting is the replacement for DCOM. As we have seen in the last chapters, ASP.NET web services

are an easy-to use-technology to call services across a network. ASP.NET web services can be used as a

communication link with different technologies, for example to have a COM or a Java client talk to web

services developed with ASP.NET. As good as this technology is, however, it is not fast and flexible enough

for some business requirements in intranet solutions, and ASP.NET web services requires the ASP.NET

runtime. With .NET Remoting we get Web Services Anywhere that can run in every application type.

Web Services Anywhere

The term "Web Services Anywhere" means that web services can not only be used in any application, but

any application can offer web services. ASP.NET web services require the IIS to run; web services that make

use of .NET Remoting can run in any application type: console applications, Windows Forms applications,

Windows services, and so on. These web services can use any transport with any payload encoding .

In the next chapter we will talk about when and how to use .NET Remoting with different transports

(TCP and HTTP) and about different payload encoding mechanisms (SOAP and binary).

CLR Object Remoting

The next part of .NET Remoting that we need to be aware of is CLR Object Remoting. With CLR

Object Remoting we can call objects across the network, as if they were being called locally.

With CLR Object Remoting we have:

❑

Distributed Identities – Remote objects can have a distributed identity. If we pass a reference

to a remote object, we will always access the same object using this reference.

❑

Activation – Remote objects can be activated using the new operator. Of course, there are

other ways to activate remote objects, as we will see later.

❑

Lease-Based Lifetime – How long should the object be activated on the server? At what time

can we assume that the client no longer needs the remote object? DCOM uses a ping

mechanism that is not scalable to internet solutions. .NET Remoting takes a different

approach with a lease-based lifetime that is scalable.

❑

Call Context – With the SOAP header, additional information can be passed with every

method call that is not passed as an argument.

We will cover all of these CLR Object Remoting features in detail later on in this chapter.

.NET Remoting Fundamentals

The methods that will be called from the client are implemented in a remote object class. In the figure

opposite we can see an instance of this class as the Remote Object. Because this remote object runs inside a

process that is different from the client process – usually also on a different system – the client can't call it

directly. Instead the client uses a proxy . For the client, the proxy looks like the real object with the same

public methods. When the methods of the proxy are called, messages will be created. These are serialized

using a formatter class, and are sent into a client channel . The client channel communicates with the server

part of the channel to transfer the message across the network. The server channel uses a formatter to

deserialize the message, so that the methods can be dispatched to the remote object :

132

.NET Remoting Architecture

Client Process

Server Process

Proxy

Remote Object

Formatter

Client Channel

Sever Channel

In the simplest case, we have to create a remote object class and instantiate a channel for a .NET

Remoting application. The formatter and the proxy will be supplied automatically. The architecture is

very flexible in that different formatters and channels can be used. We cover the use of the TCP and

HTTP channels, and the SOAP and binary formatters in the next chapter.

In the next section we'll start with the simplest case to develop a remoting object, server, and client. In

this section we will not go into the details of the remoting architecture, as we will cover this later after

we've finished a simple client and server.

Remote Object

A remote object is implemented in a class that derives from System.MarshalByRefObject .

MarshalByRefObject defines methods for lifetime services that will be described later when we use

the leasing features. A remote object is confined to the application domain where it is created. As we

already know, a client doesn't call the methods directly; instead a proxy object is used to invoke

methods on the remote object. Every public method that we define in the remote object class is

available to be called from clients.

What is an application domain ? Before .NET, processes were used as a security boundary so that one

process couldn't crash another process because it used private virtual memory. With the help of the

managed environment of .NET, the code of an application can be checked, and there's no way to crash the

process. To reduce the overhead with different processes, the concept of an application domain was

introduced with .NET. Multiple applications can run in the same process without influencing each other

if they are called within different application domains. If one of these applications throws an exception

that isn't handled, only the application domain is terminated, and not the complete process. To invoke a

method in an object running in a different application domain, .NET remoting must be used.

The following code sample shows a simple remote object class, and the code for this simple example can be

found in the SimpleTest folder of the code download for this chapter, which is available from

http://www.wrox.com . The method Hello() is declared public to make it available for a remoting client:

// MyRemoteObject.cs

using System;

namespace Wrox.Samples

{

133

WROX - C# Web Services - Building Web Services with ASP.NET and.NET Remoting.pdf

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: