Componentes .net

Example .NET Remoting
Johann Oberleitner Zürich 2007

Goal:
◦ Develop a Sample Application for .NET ◦ Let the application use .NET Remoting

.NET Remoting
Comparable to Java RMI
◦ more flexible ◦ more extensible

Example
AppDomain (on one host)

ICalculator

Client

CalculatorImpl

Example
public interface ICalculator { int Add(int a, int b); // a+b int Sub(int a, int b); //a-c } public class CalculatorImpl: ICalculator { int Add(int a, int b) { return a+b; } int Sub(int a, int b) { return a-b; } }

Make Example Remoteable
AppDomain (on one host) AppDomain (on other host)

ICalculator

Client

CalculatorImpl

Example
public Client { ICalculator calculator; public void Init() { calculator = new CalculatorImpl(); } public void Testcalcs() { int a=3, b=5;Console.Out.WriteLine("{0}+{1}={2}",a, b, calculator.Add(a,b)); } }

Make Calculator Example Remote
public class CalculatorImpl: MarshalByRefObject, ICalculator { … // unchanged }

Make Example Remoteable
Server requires application that
◦ Registers available Remoteable classes
Only done once per server

Client registration
Client needs to get informed of services
◦ Once per client ◦Programmatically or via configuration file

◦ Stays in memory
Eg. Waits until user hits a key on server machine

Example - Server
public class Server { static void Main(string[] args) { HttpChannel myChannel = new HttpChannel(3333); ChannelServices.RegisterChannel (myChannel); RemotingConfiguration.RegisterWellKnownServiceType( typeof(CalculatorImpl), "MyCalculator",WellKnownObjectMode.Singleton); System.Console.WriteLine("Press Enter to exit!"); System.Console.ReadLine(); } }

Example - Client
public class Client { static void Main(string[] args) { HttpChannel myChannel = new HttpChannel(0); ChannelServices.RegisterChannel (myChannel); WellKnownClientTypeEntry remoteType = new WellKnownClientTypeEntry( typeof(CalculatorImpl), "http://localhost:4000/MyCalculator"); … // as before} }

Alternatives for Server
Instead of programmatic registering
◦ Loading registration from a Remoting Configuration file (XML) ◦ Can also be done at the client

.NET Application Domains
Application Domain like a logical process
◦ cannot access directly data (objects) in another application domain

.NET Remoting has to be used for communication across application domains
Same hostDifferent host

Instead of Waiting for a key
◦ Implement Calculator as a Windows Service started at system startup-time ◦ .NET Remoting Services may be hosted in Internet Information Server (IIS)
Restricted to HTTP transformation model

◦ Relevant when object references are transfered

.NET Contexts
◦ Similar to Application Domain but at smaller granularity ◦ Objects extendsContextBoundObject ◦ Special treatment when context is entered/left on calls

.NET Remoting
Microsoft's technology for distributed object communication in .NET
◦ ◦ ◦ ◦ Very flexible Very extensible No relation to COM/DCOM(!) Simple

.NET Remoting Object Types - Server activated
Singleton
◦ No more than one instance can be active
Implicitly created on first client call

◦ Can maintain state betweenmethod calls ◦ Multiple clients may be supported via multithreading ◦ Lifetime management

Single-Call
◦ New instance for every invocation of a method call ◦ After method call instance will be recycled ◦ No state may be maintained between calls
Stateless programming model improves scalability

◦ In theory load balancing possible

.NET Remoting Object Types - Client activatedClient-Activated
◦ Instance is created by client ◦ Instance reference is maintained by client
Client maintains a proxy Each instance is Referred to by a unique URI Server runs still on server

Object Lifetime
Lifetime management of .NET remoting objects based on leases
◦ Lease time (default 5minutes) expires
Object gets garbage collected

◦ When client makes a call lease gets increased (default...