JAVA设计模式之责任链模式

责任链模式：是一种对象的行为模式。在责任链模式里，很多对象由每一个对象对其下家的引用而连接起来形成一条链。请求在这个链上传递，直到链上的某一个对象决定处理此请求。发出这个请求的客户端并不知道链上的哪一个对象最终处理这个请求，这使得系统可以在不影响客户端的情况下动态地重新组织和分配责任。

简单例子：

public class Request 
{
    private String name;
    private String reason;
    private int duration;

    public String getName() 
    {
        return name;
    }
    
    public void setName(String name) 
    {
        this.name = name;
    }
    
    public String getReason() 
    {
        return reason;
    }
    
    public void setReason(String reason)
    {
        this.reason = reason;
    }

    public int getDuration() 
    {
        return duration;
    }

    public void setDuration(int duration) 
    {
        this.duration = duration;
    }
}

public abstract class Handler 
{
    protected Handler successor;

    public void setSuccessor(Handler successor)
    {
        this.successor = successor;
    }

    public abstract void handle(Request request);
}

public class Supvisor extends Handler
{
    @Override
    public void handle(Request request) 
    {
        if(request.getDuration() <= 1)
        {
            System.out.println("Supvisor will handle this request.");
        }
        else
        {
            System.out.println("Supvisor submits this request to ProjectManager.");
            successor.handle(request);
        }
    }
}

public class ProjectManager extends Handler
{
    @Override
    public void handle(Request request) 
    {
        if(request.getDuration() <= 5)
        {
            System.out.println("ProjectManager will handle this request.");
        }
        else
        {
            System.out.println("ProjectManager submits this request to DepartmentManager.");
            successor.handle(request);
        }
    }
}

public class DepartmentManager extends Handler
{
    @Override
    public void handle(Request request) 
    {
        System.out.println("Although busy, DepartmentManager must handle this request.");
    }
}

public class Test 
{
    public static void main(String[] args)
    {
        Request req = new Request();
        req.setName("hxy");
        req.setReason("have a fever");
        req.setDuration(7);
        
        Handler dm = new DepartmentManager();
        Handler pm = new ProjectManager();
        pm.setSuccessor(dm);
        Handler sup = new Supvisor();
        sup.setSuccessor(pm);
        
        sup.handle(req);
    }
}