总纲

• 设计原则：遵循迪米特
• 常用场景：一个请求的处理需要多个对象当中的一个或几个协作处理
• 使用概率：15%
• 复杂度：中
• 变化点：处理链的长度与次序
• 选择关键点：对于每一次请求是否每个处理的对象都需要一次处理机会
• 逆鳞：无
• 定义：为了避免请求的发送者和接收者之间的耦合关系，使多个接受对象都有机会处理请求。将这些对象连成一条链，并沿着这条链传递该请求，直到有一个对象处理它为止

责任链模式

 //订单类（相当于request，其实就是封装一个请求）
    public class Order {

        private int x;
        private int y;
        private Map<String, Integer> order;

        public Order(int x, int y, Map<String, Integer> order) {
            super();
            this.x = x;
            this.y = y;
            this.order = order;
        }

        public int getX() {
            return x;
        }

        public void setX(int x) {
            this.x = x;
        }

        public int getY() {
            return y;
        }

        public void setY(int y) {
            this.y = y;
        }

        public Map<String, Integer> getOrder() {
            return order;
        }

        public void setOrder(Map<String, Integer> order) {
            this.order = order;
        }

    }

    //分店接口（相当于Hanlder）
    public interface Subbranch {

        void setSuccessor(Subbranch subbranch);

        boolean handleOrder(Order order);

    }

    //麦当劳分店
    public class McSubbranch implements Subbranch{

        private final static int MIN_DISTANCE = 500;//假设是500米以内送餐

        private static int count;//类计数

        private final int number;//分店号

        private int x;//分店的横坐标，用于判断距离

        private int y;//分店的纵坐标，用于判断距离

        private Map<String, Integer> menu;//菜单

        private Subbranch nextSubbranch;//下一家分店

        public McSubbranch(int x, int y, Map<String, Integer> menu) {
            super();
            this.x = x;
            this.y = y;
            this.menu = menu;
            number = ++count;
        }
        //设置下一家分店
        public void setSuccessor(Subbranch subbranch) {
            this.nextSubbranch = subbranch;
        }
        //按照职责链处理订单
        public boolean handleOrder(Order order){
            //如果距离小于500米并且订单中的食物不缺货，则订单成功，否则失败
            if (CommonUtils.getDistance(order.getX(), order.getY(), this.x, this.y) < MIN_DISTANCE && !CommonUtils.outOfStock(menu, order.getOrder())) {
                for (String name : order.getOrder().keySet()) {
                    menu.put(name, menu.get(name) - order.getOrder().get(name));
                }
                System.out.println("订餐成功，接受订单的分店是：" + this);
                return true;
            }
            if (nextSubbranch == null) {
                return false;
            }
            return nextSubbranch.handleOrder(order);
        }

        public Map<String, Integer> getMenu() {
            return Collections.unmodifiableMap(menu);
        }

        public Subbranch getNextSubbranch() {
            return nextSubbranch;
        }

        public String toString() {
            return "麦当劳分店第" + number + "个";
        }


    }

    public class Client {

        public static void main(String[] args) {
            //假设初始菜单都是以下这些东西
            Map<String, Integer> menu = new HashMap<String, Integer>();
            menu.put("汉堡", 5);
            menu.put("薯条", 5);
            menu.put("可乐", 5);
            menu.put("雪碧", 5);
            //假设有5个分店
            Subbranch mcSubbranch1 = new McSubbranch(0, 0, new HashMap<String, Integer>(menu));
            Subbranch mcSubbranch2 = new McSubbranch(100, 120, new HashMap<String, Integer>(menu));
            Subbranch mcSubbranch3 = new McSubbranch(-100, -120, new HashMap<String, Integer>(menu));
            Subbranch mcSubbranch4 = new McSubbranch(1000, 20, new HashMap<String, Integer>(menu));
            Subbranch mcSubbranch5 = new McSubbranch(-500, 0, new HashMap<String, Integer>(menu));

            //以下设置职责链
            mcSubbranch4.setSuccessor(mcSubbranch5);
            mcSubbranch3.setSuccessor(mcSubbranch4);
            mcSubbranch2.setSuccessor(mcSubbranch3);
            mcSubbranch1.setSuccessor(mcSubbranch2);
            //小左开始订餐，假设小左的坐标是900,20 
            Map<String, Integer> order = new HashMap<String, Integer>();
            order.put("汉堡", 2);
            order.put("可乐", 1);
            order.put("薯条", 1);

            print(mcSubbranch1);
            System.out.println("------------------------------------------");

            //小左开始订餐，直接找mcSubbranch1的这一家分店订餐即可
            mcSubbranch1.handleOrder(new Order(900, 20, order));

            System.out.println("------------------------------------------");
            print(mcSubbranch1);
        }

        public static void print(Subbranch subbranch){
            if (subbranch == null ) {
                return;
            }
            do {
                if (subbranch instanceof McSubbranch) {
                    System.out.println("[" + subbranch + "]的菜单:" + ((McSubbranch) subbranch).getMenu());
                }
            } while ((subbranch = ((McSubbranch) subbranch).getNextSubbranch()) != null);
        }

    }