定义通过让不只一个对象处理同一请求从而避免请求发送者和接受者的一一绑定。所有接受者形成处理链，沿着处理链传递请求直到某个对象处理该请求。
使用频度:
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中低
UML 类图
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参与者
该模式参与的类或对象
- ConcreteHandler(具体处理器，如董事，副主席，主席)
- 如果该处理器能处理该请求则处理，否则传递到后继处理器
C# 实例代码
// Chain of Responsibility pattern -- Structural example
using System;
namespace DoFactory.GangOfFour.Chain.Structural
{
///
/// MainApp startup class for Structural
/// Chain of Responsibility Design Pattern.
///
class MainApp
{
///
/// Entry point into console application.
///
static void Main()
{
// Setup Chain of Responsibility
Handler h1 = new ConcreteHandler1();
Handler h2 = new ConcreteHandler2();
Handler h3 = new ConcreteHandler3();
h1.SetSuccessor(h2);
h2.SetSuccessor(h3);
// Generate and process request
int[] requests = { 2, 5, 14, 22, 18, 3, 27, 20 };
foreach (int request in requests)
{
h1.HandleRequest(request);
}
// Wait for user
Console.ReadKey();
}
}
///
/// The 'Handler' abstract class
///
abstract class Handler
{
protected Handler successor;
public void SetSuccessor(Handler successor)
{
this.successor = successor;
}
public abstract void HandleRequest(int request);
}
///
/// The 'ConcreteHandler1' class
///
class ConcreteHandler1 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 0 && request < 10)
{
Console.WriteLine("{0} handled request {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
///
/// The 'ConcreteHandler2' class
///
class ConcreteHandler2 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 10 && request < 20)
{
Console.WriteLine("{0} handled request {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
///
/// The 'ConcreteHandler3' class
///
class ConcreteHandler3 : Handler
{
public override void HandleRequest(int request)
{
if (request >= 20 && request < 30)
{
Console.WriteLine("{0} handled request {1}",
this.GetType().Name, request);
}
else if (successor != null)
{
successor.HandleRequest(request);
}
}
}
}
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输出:
ConcreteHandler1 handled request 2
ConcreteHandler1 handled request 5
ConcreteHandler2 handled request 14
ConcreteHandler3 handled request 22
ConcreteHandler2 handled request 18
ConcreteHandler1 handled request 3
ConcreteHandler3 handled request 27
ConcreteHandler3 handled request 20
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