Design Mode: Singleton mode and Design Mode

Design Mode: Singleton mode and Design Mode

1. Class Diagram

Instance Diagram

2. Create a project

....................................

3. Create a weekly report class LoadBalancer: A Load balancer class that acts as a singleton. In a real environment, this class is very complex, including a large number of initialization work and business methods. Considering the readability and comprehensibility of the Code, only some core Code related to the mode is listed here.

Using System;

Using System. Collections;

Using System. Threading;

Namespace SingletonSample

{

Class LoadBalancer

{

// Private Static member variable to store unique instances

Private static LoadBalancer instance = null;

// Server set

Private ArrayList serverList = null;

 

// Private constructor

Private LoadBalancer ()

{

ServerList = new ArrayList ();

}

// Public static member method, returns a unique instance

Public static LoadBalancer GetLoadBalancer ()

{

If (instance = null)

{

Instance = new LoadBalancer ();

}

Return instance;

}

// Add servers

Public void AddServer (string server)

{

ServerList. Add (server );

}

// Delete the server

Public void RemoveServer (string server)

{

ServerList. Remove (server );

}

// Use the Random class to randomly retrieve the server

Public string GetServer ()

{

Random random = new Random ();

Thread. Sleep (10); // a moderate Thread wait can ensure that the random number is not the last result.

Int I = random. Next (serverList. Count );

Return serverList [I]. ToString ();

}

}

}

4. Create a Singleton class:

Using System;

Using System. Collections. Generic;

Using System. Linq;

Using System. Text;

Namespace SingletonSample

{

Public class Singleton

{

Private static Singleton _ singleton = null; // defines a private static member variable-a unique instance object

 

/// <Summary>

/// Define private constructor to prevent external instantiation

/// </Summary>

Private Singleton ()

{

}

/// <Summary>

/// Define the public unique orientation (factory) method, return to the unique instance of the system, and create your own

/// </Summary>

/// <Returns> </returns>

Public static Singleton GetInstance ()

{

If (_ singleton = null)

_ Singleton = new Singleton (); // if it is null, instantiate itself

Return _ singleton;

}

}

}

 

5. Program: client test class

Using System;

Namespace SingletonSample

{

Class Program

{

Static void Main (string [] args)

{

# Region test Singleton to check whether the same instance is used

Singleton singleton1 = Singleton. GetInstance (); // create a Singleton object 1

Singleton singleton2 = Singleton. GetInstance (); // create a Singleton object 1

If (singleton1 = singleton2)

{

Console. WriteLine ("singleton1 and singleton2 are the same instance. ");

}

Else

{

Console. WriteLine ("singleton1 and singleton2 are: not the same instance. ");

}

Console. Read ();

# Endregion

# Region case

// Create four LoadBalancer objects

LoadBalancer balancer1, balancer2, balancer3, balancer4;

Balancer1 = LoadBalancer. GetLoadBalancer ();

Balancer2 = LoadBalancer. GetLoadBalancer ();

Balancer3 = LoadBalancer. GetLoadBalancer ();

Balancer4 = LoadBalancer. GetLoadBalancer ();

// Determine whether the Server Load balancer is the same

If (balancer1 = balancer2 & balancer2 = balancer3 & balancer3 = balancer4)

{

Console. WriteLine ("Server Load balancer is unique! ");

}

// Add servers

Balancer1.AddServer ("Server 1 ");

Balancer1.AddServer ("Server 2 ");

Balancer1.AddServer ("Server 3 ");

Balancer1.AddServer ("Server 4 ");

// Simulate the distribution of client requests. If the output result is all the same server, you can enlarge the I as needed, for example, changing it to "I <100"

Int num = 10;

For (int I = 0; I <num; I ++)

{

String server = balancer1.GetServer ();

Console. WriteLine ("Distribute request to server:" + server );

}

Console. Read ();

# Endregion

}

}

}