深入Java设计模式之责任链模式

责任链模式原理

如果有多个对象都有机会处理请求，责任链可使请求的发送者和接收者解耦，请求沿着责任链传递，直到有一个对象处理了它为止。

责任链模式优缺点

优点：  将请求的发送者和接收者解耦，使多个对象都有机会处理这个请求  可以简化对象，因为它无须知道链的结构  可以动态地增加或删减处理请求的链结构

缺点：  请求从链的开头进行遍历，对性能有一定的损耗  并不保证请求一定被处理 

适用场合

 有多个对象可以处理一个请求  不明确接收者的情况  有序、无序链，线型、树形、环形链

责任链模式和状态模式主要区别

 责任链模式注重请求的传递  状态模式注重对象状态的转换

责任链模式示例代码

购买请求决策项目介绍

 场景：财务审批  
 1.小组领导接到的审批 小于5000小组领导审批,否则执行2
 2.部门领导接到的审批 大于5000 且小于10000部门领导审批,否则执行3
 3.副主席接到的审批     大于10000且小于50000副主席审批,否则执行4
 4.主席接到的审批         大于50000主席审批,否则执行1

考虑扩展性 思考如何设计

package com.lzhsite.technology.designPattern.chainms;


public class MainTest {

	public static void main(String[] args) {
		
		Client mClient = new Client();
		Approver GroupLeader = new GroupApprover("Tom");
		Approver VicePresident = new VicePresidentApprover("Kate");
		Approver DepartmentLeader = new DepartmentApprover("Jerry");
		Approver President = new PresidentApprover("Bush");
		
		GroupLeader.SetSuccessor(DepartmentLeader);
		DepartmentLeader.SetSuccessor(VicePresident);
		VicePresident.SetSuccessor(President);
		President.SetSuccessor(GroupLeader);
		
		VicePresident.ProcessRequest(mClient.sendRequst(1, 100, 40));
		VicePresident.ProcessRequest(mClient.sendRequst(2, 200, 40));
		VicePresident.ProcessRequest(mClient.sendRequst(3, 300, 40));
		VicePresident.ProcessRequest(mClient.sendRequst(4, 400, 140));
		
	}


}

package com.lzhsite.technology.designPattern.chainms;

public abstract class Approver {
	 Approver successor;
	 String Name;
	public Approver(String Name)
	{
		this.Name=Name;
	}
	public abstract void ProcessRequest( PurchaseRequest request);
	public void SetSuccessor(Approver successor) {
		// TODO Auto-generated method stub
		this.successor=successor;
	}
}

package com.lzhsite.technology.designPattern.chainms;
/**
 * 组内领导审批
 * @author lzhcode
 *
 */
public class GroupApprover extends Approver {

	public GroupApprover(String Name) {
		super(Name+" GroupLeader");
		// TODO Auto-generated constructor stub
		
	}

	@Override
	public void ProcessRequest(PurchaseRequest request) {
		// TODO Auto-generated method stub

		if (request.GetSum() < 5000) {
			System.out.println("**This request " + request.GetID()
					+ " will be handled by "
					+ this.Name + " **");
		} else {
			successor.ProcessRequest(request);
		}
	}

}

package com.lzhsite.technology.designPattern.chainms;
/**
 * 部门领导审批
 * @author lzhcode
 *
 */
public class DepartmentApprover extends Approver {

	public DepartmentApprover(String Name) {
		super(Name + " DepartmentLeader");

	}

	@Override
	public void ProcessRequest(PurchaseRequest request) {
		// TODO Auto-generated method stub

		if ((5000 <= request.GetSum()) && (request.GetSum() < 10000)) {
			System.out.println("**This request " + request.GetID()
					+ " will be handled by " + this.Name + " **");
		} else {
			successor.ProcessRequest(request);
		}

	}

}

package com.lzhsite.technology.designPattern.chainms;
/**
 * 副总经理审批
 * @author lzhcode
 *
 */
public class VicePresidentApprover extends Approver {

	public VicePresidentApprover(String Name) {
		super(Name + " Vice President");
	}

	@Override
	public void ProcessRequest(PurchaseRequest request) {
		// TODO Auto-generated method stub
		if ((10000 <= request.GetSum()) && (request.GetSum() < 50000)) {
			System.out.println("**This request " + request.GetID()
					+ " will be handled by " + this.Name + " **");
		} else {
			successor.ProcessRequest(request);
		}
	}

}

package com.lzhsite.technology.designPattern.chainms;
/**
 * 副总经理审批
 * @author lzhcode
 *
 */
public class VicePresidentApprover extends Approver {

	public VicePresidentApprover(String Name) {
		super(Name + " Vice President");
	}

	@Override
	public void ProcessRequest(PurchaseRequest request) {
		// TODO Auto-generated method stub
		if ((10000 <= request.GetSum()) && (request.GetSum() < 50000)) {
			System.out.println("**This request " + request.GetID()
					+ " will be handled by " + this.Name + " **");
		} else {
			successor.ProcessRequest(request);
		}
	}

}

package com.lzhsite.technology.designPattern.chainms;

public class Client {

	public Client() {

	}

	public PurchaseRequest sendRequst(int Type, int Number, float Price) {
		return new PurchaseRequest(Type, Number, Price);
	}

}

package com.lzhsite.technology.designPattern.chainms;

public class PurchaseRequest {
	private int Type = 0;
	private int Number = 0;
	private float Price = 0;
	private int ID = 0;

	public PurchaseRequest(int Type, int Number, float Price) {
		this.Type = Type;
		this.Number = Number;
		this.Price = Price;
	}

	public int GetType() {
		return Type;
	}

	public float GetSum() {
		return Number * Price;
	}

	public int GetID() {
		return (int) (Math.random() * 1000);
	}
}