/**
 * 支付渠道
 * .
 */
public abstract class Payment {
    //支付类型
    public abstract String getName();
    //查询余额
    protected abstract double queryBalance(String uid);
    //扣款支付
    public MsgResult pay(String uid, double amount) {
        if(queryBalance(uid) < amount){
            return new MsgResult(500,"支付失败","余额不足");
        }
        return new MsgResult(200,"支付成功","支付金额：" + amount);
    }
}

public class JDPay extends Payment {
    public String getName() {
        return "京东白条";
    }
    protected double queryBalance(String uid) {
        return 500;
    }
}

public class AliPay extends Payment {
    public String getName() {
        return "支付宝";
    }
    protected double queryBalance(String uid) {
        return 900;
    }
}

public class UnionPay extends Payment {
    public String getName() {
        return "银联支付";
    }
    protected double queryBalance(String uid) {
        return 120;
    }
}

public class WechatPay extends Payment {
    public String getName() {
        return "微信支付";
    }
    protected double queryBalance(String uid) {
        return 256;
    }
}

public class PayStrategy {
    public static final String ALI_PAY = "AliPay";
    public static final String JD_PAY = "JdPay";
    public static final String UNION_PAY = "UnionPay";
    public static final String WECHAT_PAY = "WechatPay";
    public static final String DEFAULT_PAY = ALI_PAY;
    private static Map<String, Payment> payStrategy = new HashMap<String, Payment>();
    static {
        payStrategy.put(ALI_PAY, new AliPay());
        payStrategy.put(WECHAT_PAY, new WechatPay());
        payStrategy.put(UNION_PAY, new UnionPay());
        payStrategy.put(JD_PAY, new JDPay());
    }
    public static Payment get(String payKey) {
        if (!payStrategy.containsKey(payKey)) {
            return payStrategy.get(DEFAULT_PAY);
        }
        return payStrategy.get(payKey);
    }
}

public class MsgResult {
    private int code;
    private Object data;
    private String msg;
    public MsgResult(int code, String msg, Object data) {
        this.code = code;
        this.data = data;
        this.msg = msg;
    }
    public String toString(){
        return ("支付状态：[" + code + "]," + msg + ",交易详情：" + data);
    }
}

public class PayStrategyTest {
    public static void main(String[] args) {
        //省略把商品添加到购物车，再从购物车下单
        //直接从点单开始
        Order order = new Order("1","20180311001000009",324.45);
        //开始支付，选择微信支付、支付宝、银联卡、京东白条、财付通
        //每个渠道它支付的具体算法是不一样的
        //基本算法固定的
        MsgResult pay = order.pay(PayStrategy.JD_PAY);
        //这个值是在支付的时候才决定用哪个值
//        System.out.println(order.pay(PayStrategy.ALI_PAY));
        System.out.println(pay);
        //java中的应用
//        Arrays.sort();
        //Resource
//        InstantiationStrategy
    }
}

compare()方法，就是一个策略抽象实现.
public class Arrays {
public static <T> void parallelSort(T[] a, int fromIndex, int toIndex,
Comparator<? super T> cmp) {
}
}

public interface Comparator<T> {
int compare(T o1, T o2);
}

public class DispatcherServlet extends HttpServlet {
    private List<Handler> handlerMapping = new ArrayList<Handler>();
    @Override
    public void init() throws ServletException {
        try {
            Class<?> memberControllerClass = MemberController.class;
            handlerMapping.add(new Handler()
                    .setController(memberControllerClass.newInstance())
                    .setMethod(memberControllerClass.getMethod("getMemberById", new Class[]{String.class}))
                    .setUrl("/web/getMemberById.json"));
        } catch (Exception e) {
        }
    }
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try {
            doDispatch(req, resp);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    private void doDispatch(HttpServletRequest request, HttpServletResponse response) throws IOException {
        //1、获取用户请求的url
        //   如果按照J2EE的标准、每个url对对应一个Serlvet，url由浏览器输入
        String uri = request.getRequestURI();
        //2、Servlet拿到url以后，要做权衡（要做判断，要做选择）
        //   根据用户请求的URL，去找到这个url对应的某一个java类的方法
        //3、通过拿到的URL去handlerMapping（我们把它认为是策略常量）
        Handler handle = null;
        for (Handler h : handlerMapping) {
            if (uri.equals(h.getUrl())) {
                handle = h;
                break;
            }
        }
        //4、将具体的任务分发给Method（通过反射去调用其对应的方法）
        Object object = null;
        try {
            object = handle.getMethod().invoke(handle.getController(), request.getParameter("mid"));
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        //5、获取到Method执行的结果，通过Response返回出去
        response.getWriter().write("");
    }
    class Handler {
        private Object controller;
        private Method method;
        private String url;
        public Object getController() {
            return controller;
        }
        public Handler setController(Object controller) {
            this.controller = controller;
            return this;
        }
        public Method getMethod() {
            return method;
        }
        public Handler setMethod(Method method) {
            this.method = method;
            return this;
        }
        public String getUrl() {
            return url;
        }
        public Handler setUrl(String url) {
            this.url = url;
            return this;
        }
    }
}