读《研磨设计模式》-代码笔记-职责链模式-Chain Of Responsibility

声明：
本文只为方便我个人查阅和理解，详细的分析以及源代码请移步 原作者的博客http://chjavach.iteye.com/

/**
 * 业务逻辑：项目经理只能处理500以下的费用申请，部门经理是1000，总经理不设限。简单起见，只同意“Tom”的申请
 * bylijinnan
 */
abstract class Handler {
	/* 持有一个同类型的引用。有点像链表。网上也有职责链和链表的分析
	 * 目前我理解两者的不同是：
	 * 1.职责链是变动的，组建职责链时可动态组合
	 * 2.链表只有一个入口，但职责链可从中间某点开始，跳过一些点
	 */
	protected Handler successor;
	
	public void setSuccessor(Handler successor) {
		this.successor = successor;
	}
	
	//可根据实际情况是否传递参数
	public abstract String handleRequest(String user, double fee);

}


//项目经理
class ProjectManager extends Handler {

	public String handleRequest(String user, double fee) {
		String result = "";
		if (fee < 500) {
			if ("Tom".equals(user)) {
				result = "ProjectManager approved. User = " + user + ", fee = " + fee;
			} else {
				result = "ProjectManager rejected. User = " + user + ", fee = " + fee;
			}
		} else {
			if (this.successor != null) {
				result = this.successor.handleRequest(user, fee);
			}
		}
		return result;
	}
	
}


//部门经理
class DivisionManager extends Handler {
	
	public String handleRequest(String user, double fee) {
		String result = "";
		if (fee < 1000) {
			if ("Tom".equals(user)) {
				result = "DivisionManager approved. User = " + user + ", fee = " + fee;
			} else {
				result = "DivisionManager rejected. User = " + user + ", fee = " + fee;
			}
		} else {
			if (this.successor != null) {
				result = this.successor.handleRequest(user, fee);
			}
		}
		return result;
	}
	
}


//总经理
class GeneralManager extends Handler {
	
	public String handleRequest(String user, double fee) {
		String result = "";
		if ("Tom".equals(user)) {
			result = "GeneralManager approved. User = " + user + ", fee = " + fee;
		} else {
			result = "GeneralManager rejected. User = " + user + ", fee = " + fee;
		}
		
		/*//我们定义总经理是这个流程的最后一环，因此就不再传递了
		if (this.successor != null) {
			result = this.successor.handleRequest(user, fee);
		}
		*/
		return result;
	}
	
}


/**
 * 扩展一：如果要新增另一个费用的审批流程呢？
 * 当然可以这样写，在Handler里面新增一个处理流程的方法：
 *	public abstract String handleAnotherRequest(String user, double whateverFee);
 * 书上介绍了另一个更易于扩展的方法，如下
 */

abstract class Handlerr {
	
	protected Handlerr successor;
	
	public void setSuccessor(Handlerr successor) {
		this.successor = successor;
	}
	
	/**
	 * 子类应该重写本方法来实现具体的业务逻辑
	 * @param requestModel	 申请业务数据类型 包括申请人、申请金额、费用类型
	 * @return	处理结果。为兼容不同的返回类型(String or boolean)，返回类型设为Object--我觉得这样不好，容易造成混乱
	 */
	public Object handleRequest(RequestModel requestModel) {
		Object result = null;
		if (successor != null) {
			result = this.successor.handleRequest(requestModel);
		} else {
			System.out.println("没有后续处理或者暂时不支持后续处理");
		}
		return result;
	}
}


//项目经理1.处理OneRequestModel的申请
class ProjectManagerr extends Handlerr {
	
	public Object handleRequest(RequestModel requestModel) {
		Object result = null;
		//假设只处理类型为OneRequestModel的申请
		if (requestModel.getRequestType() == OneRequestModel.TYPE_ONE) {
			result = this.handleTypeOneRequest(requestModel);
		} else {
			result = super.handleRequest(requestModel);
		}
		return result;
	}
	
	private Object handleTypeOneRequest(RequestModel requestModel) {
		String result = null;
		//这里面的业务逻辑跟之前的ProjectManager是一样的
		if (requestModel.getFee() < 500) {
			if ("Tom".equals(requestModel.getUser())) {
				result = "ProjectManager approved. RequestModel = " + requestModel;
			} else {
				result = "ProjectManager rejected. RequestModel = " + requestModel;
			}
		} else {
			if (this.successor != null) {
				return this.successor.handleRequest(requestModel);
			}
		}
		return result;
	}
}


//项目经理2.处理AnotherRequestModel的申请
class ProjectManagerr2 extends ProjectManagerr {
	
	public Object handleRequest(RequestModel requestModel) {
		Object result = false;
		//假设只处理类型为AnotherRequestModel的申请
		if (requestModel.getRequestType() == AnotherRequestModel.TYPE_ANOTHER) {
			result = this.handleTypeAnotherRequest(requestModel);
		} else {
			result = super.handleRequest(requestModel);
		}
		return result;
	}
	
	private Object handleTypeAnotherRequest(RequestModel requestModel) {
		boolean result = false;
		//这里面的业务逻辑跟之前的ProjectManager是一样的
		if (requestModel.getFee() < 500) {
			if ("Tom".equals(requestModel.getUser())) {
				result = true;
				System.out.println("ProjectManager2 approved. RequestModel = " + requestModel);
			} else {
				result = false;
				System.out.println("ProjectManager2 rejected. RequestModel = " + requestModel);
			}
		} else {
			if (this.successor != null) {
				return this.successor.handleRequest(requestModel);
			}
		}
		return result;
	}
}


class RequestModel {
	
	private String user;		//申请人
	private double fee;		//费用
	private int requestType;		//费用类型
	
	public RequestModel(String user, double fee, int requestType) {
		this.user = user;
		this.fee = fee;
		this.requestType = requestType;
	}
	

	public String getUser() {
		return user;
	}

	public double getFee() {
		return fee;
	}

	public int getRequestType() {
		return requestType;
	}
	
	public void setUser(String user) {
		this.user = user;
	}


	public void setFee(double fee) {
		this.fee = fee;
	}


	public void setRequestType(int requestType) {
		this.requestType = requestType;
	}

	public String toString() {
		return "user = " + this.user + ",fee = " + this.fee + ",requestType = " + this.requestType;
	}
}


class OneRequestModel extends RequestModel {

	public static int TYPE_ONE  = 1;
	
	public OneRequestModel(String user, double fee, int requestType) {
		super(user, fee, TYPE_ONE);
	}
	
}


class AnotherRequestModel extends RequestModel {
	
	public static int TYPE_ANOTHER  = 2;
	
	public AnotherRequestModel(String user, double fee, int requestType) {
		super(user, fee, TYPE_ANOTHER);
	}
	
}

/**
 * 扩展二：功能链。比较典型的应用是Java Web开发里面的filter
 * 业务逻辑：保存销售信息。保存之前要进行权限检查和数据检查
 */

class GoodsSaleBO {
	
	/**
	 * 保存商品销售信息
	 * @param user	销售人员
	 * @param customer	客户
	 * @param saleModel
	 * @return true-保存成功 false-保存失败
	 */
	public boolean save(String user, String customer, SaleModel saleModel) {
		//构建功能链
		PrivilegeCheckSaleHandler privilegeCheckSaleHandler = new PrivilegeCheckSaleHandler();
		DataCheckSaleHandler dataCheckSaleHandler = new DataCheckSaleHandler();
		DataSaveSaleHandler dataSaveSaleHandler = new DataSaveSaleHandler();
		privilegeCheckSaleHandler.setSuccessor(dataCheckSaleHandler);
		dataCheckSaleHandler.setSuccessor(dataSaveSaleHandler);
		
		return privilegeCheckSaleHandler.save(user, customer, saleModel);
	}
}


abstract class SaleHandler {
	
	protected SaleHandler successor;
	
	public void setSuccessor(SaleHandler successor) {
		this.successor = successor;
	}
	
	public abstract boolean save(String user, String customer, SaleModel saleModel);
}


//权限检查
class PrivilegeCheckSaleHandler  extends SaleHandler {
	
	public boolean save(String user, String customer, SaleModel saleModel) {
		if ("Tom".equals(user)) {
			return this.successor.save(user, customer, saleModel);
		} else {
			System.out.println("对不起，" + user + "，您没有保存销售信息的权限");
			return false;
		}
	}
}


//数据检查
class DataCheckSaleHandler extends SaleHandler {

	public boolean save(String user, String customer, SaleModel saleModel) {
		if (emptyStr(user)) {
			System.out.println("操作人不能为空");
			return false;
		}
		if (emptyStr(customer)) {
			System.out.println("客户不能为空");
			return false;
		}
		if (saleModel == null || emptyStr(saleModel.getGoods()) || 0 == saleModel.getSoldNum()) {
			System.out.println("SaleModel数据有误");
			return false;
		}
		return this.successor.save(user, customer, saleModel);
	}
	
	private boolean emptyStr(String str) {
		return str == null || str.trim().length() == 0;
	}
	
}


//真正保存的操作
class DataSaveSaleHandler extends SaleHandler {

	public boolean save(String user, String customer, SaleModel saleModel) {
		System.out.println(user + "保存了如下信息：客户--" + customer + "，销售数据-- " + saleModel);
		return true;
	}
	
}



class SaleModel {
	
	private String goods;		//商品名称
	private int soldNum;		//销售数量
	
	public String getGoods() {
		return goods;
	}
	public void setGoods(String goods) {
		this.goods = goods;
	}
	public int getSoldNum() {
		return soldNum;
	}
	public void setSoldNum(int soldNum) {
		this.soldNum = soldNum;
	}
	public String toString() {
		return "goods = " + this.goods + ",soldNum = " + this.soldNum;
	}
}



/**
 * 这个类是用来测试的
 */
public class ChainOfResponsibilityPattern {

	public static void main(String[] args) {
		//测试费用（一种费用）申请
		ProjectManager projectManager = new ProjectManager();
		DivisionManager divisionManager = new DivisionManager();
		GeneralManager generalManager = new GeneralManager();
		projectManager.setSuccessor(divisionManager);
		divisionManager.setSuccessor(generalManager);
		
		System.out.println(projectManager.handleRequest("Tom", 499));
		System.out.println(projectManager.handleRequest("Tom", 999));
		System.out.println(projectManager.handleRequest("Tom", 1999));
		
		System.out.println(projectManager.handleRequest("James", 499));
		System.out.println(projectManager.handleRequest("James", 999));
		System.out.println(projectManager.handleRequest("James", 1999));
		
		//测试“功能链”：保存销售信息
		SaleModel saleModel = new SaleModel();
		saleModel.setGoods("iphone5");
		saleModel.setSoldNum(10);
		GoodsSaleBO goodsSaleBO = new GoodsSaleBO();
		goodsSaleBO.save("Tom", "Mr.Lee", saleModel);
		goodsSaleBO.save("Jack", "Mr.Lee", saleModel);
		
	}

}