Bài giảng Công nghệ lập trình tiên tiến: Chương 5 trình bày các kiến thức về lập trình trong .Net Remoting như đặc điểm, công dụng, câu lệnh, cú pháp,... Đây là tài liệu dành cho sinh viên ngành Công nghệ thông tin.
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Nội dung Text: Bài giảng Công nghệ lập trình tiên tiến: Chương 5 - ĐH Công nghệ Đồng Nai
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
.NET
Remoting
1
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Net Remoting Definition:
• Application which is located in another
application domain or process can
communicate with another by using .Net
Remoting.
• Net Remoting allows processes to share
the objects. It can call the method and can
access the properties of an objects that
are:
2
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Ø
Hosted in different application domain
with in the same process or
Ø
Different process executing on same
computer or
Ø
Different computers connected by LAN
or
Ø
Different computer distributed over world
wide
3
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Modern applications are no longer stand-alone
applications. - Provides a solution for
communication between
application domains
.NET Remoting:
4
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
You known Application Domain ?:
Application domain is the collection of
classes, which isolate these from other
applications. The application in one
application domain could not access the
application in other application domain
(without using Remoting)
5
- 2 Object type
DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Remotable • It can be accessed outside its
Object application domain.
Ø
CLR objects cannot, by default, be
used outside their AppDomain
- No way to copy them
Non - No way to reference them
Remotable Ø
Exception occurs when you try to
Object pass an object reference to a different
domain
Ø
SO: It can not be accessed outside
its own application domain.
6
- Remotable Object:
DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Ø
Can request that instances of a class be
accessible outside original AppDomain
– Client get a copy of the object
– Client get a reference (proxy) to the
original object
Ø
When an object is Remotable?
The object should inherit the class
System.MarshalByRefObject
Ø
Two Types of Remotable Objects are there
– Marshal by Value
– Marshal by Reference
*More detail later 7
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Object Serialization:
Conversion of an object (instance) into a data
stream of bytes, Serialization is a method of
persisting objects for storage in a database, to
various media, or during marshaling—the
process of moving an object to a new
application domain, context, process, or
system. Serialization is performed by the
Common Language Runtime (CLR).
8
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
MarshalByRef objects:
Ø
When the object's class derives, directly or
indirectly, from MarshalByRefObject, the
runtime creates a proxy to the object
[Serializable]
class Foo : System.MarshalByRefObject
{
. . .
}
Ø
Clients in foreign AppDomains receive
proxy
Ø
How does a client specify what proxy?
9
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Serializable objects:
Ø
When runtime can make a copy of the object,
an object can marshal-by-value to other
AppDomains
– Add SerializableAttribute
– Or implement the ISerializable interface
[Serializable]
Class Far {
. . .
}
10
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Remoting in general :
q
Clients must connect to servers
Ø
Server needs to publish an object
• I listen on this TCP channel and that HTTP
channel
• I have a service called "MathService"
• When client connects to MathService using
a supported channel, give the client [ a | this ]
Calculator instance
Ø
Clients need to specify the desired object
• Connect to the "MathService" on server
"LightningFast" using protocol HTTP on port 80
11
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
ASP.NET Web services (WS)
vs
.NET Remoting (NR)
See next slide…
12
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
1. WS: only be accessed over HTTP; NR
various protocols like TCP, HTTP etc.
2. WS stateless environment, NR state
management
3. WS more reliable than .NET Remoting.
4. WS are easy to create and use, NR are
complex to be created.
5. WS across platforms, NR requires client
to be built using .NET
6. WS support datatypes defined in the XSD
type system while .NET remoting provides
support for rich type system using binary
communication.
13
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
.Net Remoting components
Ø
A remotable object.
Ø
A host application.
– listen to requests for the hosted
remotable object.
Ø
A client application.
– requests for the remotable object.
14
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
How Does .NET Remoting Works?
Ø
In the client
– create a new remotable object
=>creates a proxy object
– When client call method => call method on
proxy=> server=> return to proxy => client
15
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Proxy
Ø
To avoid conjunction in networking. It
contains reference to all methods and
properties of object. There are two type of
proxy.
– Transparent proxy (There is no physical
existence, Created by IISserver)
– Real Proxy (Physical Existence)
16
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Ø
Remoting makes an object in server
available to code in client => marshalling
Ø
2 ways to marshal an object
– Marshal by value
• the server creates a copy of the object
passes the copy to the client
– Marshal by reference
• the client creates a proxy for the object
and then uses the proxy to access the
object
17
- Marshal by reference
DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Ø
2 types
– Server-Activated Objetcs (SAO)
– Client-Activated Objects (CAO)
Ø
Client-Activated Object:
– Server side object creation is handled by client application.
– An instance of object is created, when the client calls the new
operator.
Ø
Server-Activated Object:
– The object is created, when the client actually invoke a
method on proxy.
– Single Call (stateless)
• This object handles one and only one request coming from
client.
– Singleton
• This can be used to retain the state across multiple
method calls. 18
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
SAO - CAO
Ø
Server-Activated
• lifetime is controlled by server
• Use when there are clients sharing the same server
object
• It’s a one-to-many relationship between the server
object and clients
– Singleton – SingleCall Is called: WellKnow object
Ø
Client-Activated Objects
• lifetime is controlled by the client
• Use when multiple server instances of the same kind
need to be run on the server at the same time
• one-to-one relationship between each server object
and its corresponding client
19
- DONG NAI UNIVERSITY OF TECHNOLOGY
HO CHI MINH UNIVERSITY OF INDUSTRY
Client-activated objects
Client-activated objects. Each
client gets an independent
object for its use. Like the
classic client-server model,
clients can still share objects.
20
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