文章目录
- 创建design-demo项目
- 创建OrderController
- 创建OrderService
- 创建OrderServiceImpl
- 创建AbstractAuditLogProcessor
- 创建AuditLog
- 创建LoginLogProcessor
- 创建OrderLogProcessor
- 创建PayLogProcessor
- 创建Order
- 创建OrderState
- 创建OrderStateChangeAction
- 创建OrderStateMachineConfig
- 创建OrderStateListener
- 创建StrategyFacade
- 创建AddFuncFactory
- 创建PayFactory
- 创建StrategyFactory
- 创建AddFuncDecorator
- 创建AbstractAddFuncDecorator
- 创建StrategyEnum
- 校验是否正常工作
创建design-demo项目
项目代码:https://gitee.com/java_wxid/java_wxid/tree/master/demo/design-demo 项目结构如下(示例):
创建OrderController
代码如下(示例):
package com.example.designdemo.controller;
import com.example.designdemo.order.pojo.Order;
import com.example.designdemo.pay.pojo.PayBody;
import com.example.designdemo.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description: 订单管理,这里简单写写,主要是设计模式,别抠细节
*/
@RestController
public class OrderController {
@Autowired
private OrderService orderService;
@GetMapping("mkOrder")
public Order createOrder(@RequestParam Integer oid) {
return orderService.createOrder(oid);
}
@PostMapping("/pay")
public Order payOrder(@RequestBody PayBody payBody){
return orderService.pay(payBody);
}
@GetMapping("/send")
public Order send(@RequestParam Integer oid) {
return orderService.send(oid);
}
@GetMapping("/receive")
public Order receive(@RequestParam Integer oid) {
return orderService.receive(oid);
}
}
创建OrderService
代码如下(示例):
package com.example.designdemo.service;
import com.example.designdemo.order.pojo.Order;
import com.example.designdemo.pay.pojo.PayBody;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 9:28
* @Description:
*/
public interface OrderService {
Order createOrder(Integer oid);
Order pay(PayBody payBody);
Order send(Integer oid);
Order receive(Integer oid);
}
创建OrderServiceImpl
代码如下(示例):
package com.example.designdemo.service.impl;
import com.example.designdemo.order.auditlog.OrderLogProcessor;
import com.example.designdemo.order.auditlog.PayLogProcessor;
import com.example.designdemo.order.pojo.Order;
import com.example.designdemo.order.pojo.OrderState;
import com.example.designdemo.order.pojo.OrderStateChangeAction;
import com.example.designdemo.pay.facade.StrategyFacade;
import com.example.designdemo.pay.pojo.PayBody;
import com.example.designdemo.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.persist.StateMachinePersister;
import org.springframework.stereotype.Service;
import java.util.ArrayList;
import java.util.List;
/**• @Author: zhiwei Liao
• @Date: 2022/9/26 21:29
• @Description:
*/
@Service
public class OrderServiceImpl implements OrderService {
@Autowired
private StateMachine<OrderState, OrderStateChangeAction> orderStateMachine;
@Autowired
private StateMachinePersister<OrderState, OrderStateChangeAction, Order> stateMachinePersister;
@Autowired
private PayLogProcessor payLogProcessor;
@Autowired
private OrderLogProcessor orderLogProcessor;
//模拟一个存储
private List orders = new ArrayList<>();
public Order createOrder(Integer oid) {
Order order = new Order();
order.setOrderState(OrderState.ORDER_WAIT_PAY);
order.setOrderId(oid);
// 创建的order是不是得入库啊?如果不入库,下次访问的时候,是不是找不到了啊。
orders.add(order); // 模拟存储到 db
orderLogProcessor.processAuditLog(“acccount”, “createOrder”, oid.toString());
return order;
}
// 将来我们删除或者增加或者修改任何关于付款的模块,无需改动service。
//不会对调用层产生任何代码的改动。
// 调用层使用我们的pay 模块,无需关系实现的逻辑,只需要将入参传给我们的pay模块即可。
public Order pay(PayBody payBody) {
// 书写我们的付款逻辑
boolean flag = false;
flag = StrategyFacade.pay(payBody);
if(flag) {
Order order = (Order) orders.get(0); // 模拟查询db代码
payLogProcessor.processAuditLog(payBody.getAccount(), “pay”, order.getOrderId().toString());
Message message = MessageBuilder
.withPayload(OrderStateChangeAction.PAY_ORDER).setHeader(“order”, order).build();
//发送消息,发送给谁?和状态机有没有关系啊? 有
if(changeStateAction(message,order)) {
return order;
}
//如果是 true,我们要保存到db
saveToDb(payBody);
}
return null;
}
private void saveToDb(PayBody payBody) {
}
public Order send(Integer oid) {
Order order = (Order) orders.get(0); // 模拟查询db代码
Message message = MessageBuilder
.withPayload(OrderStateChangeAction.SEND_ORDER).setHeader(“order”, order).build();
if(changeStateAction(message,order)) {
return order;
}
return null;
}
public Order receive(Integer oid) {
Order order = (Order) orders.get(0); // 模拟查询db代码
Message message = MessageBuilder
.withPayload(OrderStateChangeAction.RECEIVE_ORDER).setHeader(“order”, order).build();
if(changeStateAction(message,order)) {
return order;
}
return null;
}
private boolean changeStateAction(Message message, Order order) {
try {
orderStateMachine.start();
stateMachinePersister.restore(orderStateMachine, order); // 待议
boolean res = orderStateMachine.sendEvent(message);
stateMachinePersister.persist(orderStateMachine, order); // 持久
return res;
} catch (Exception e) {
e.printStackTrace();
} finally {
orderStateMachine.stop();
}
return false;
}
}
创建AbstractAuditLogProcessor
代码如下(示例):
package com.example.designdemo.order.auditlog;
import com.example.designdemo.order.auditlog.pojo.AuditLog;
import java.util.Date;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:
*/
public abstract class AbstractAuditLogProcessor {
// 创建我们的 AuditLog (基础部分)
public final AuditLog buildAuditLog(String account, String action, String orderId){
AuditLog auditLog = new AuditLog();
auditLog.setAccount(account);
auditLog.setAction(action);
auditLog.setOrderId(orderId);
auditLog.setDate(new Date());
return auditLog;
}
protected abstract AuditLog buildDetails(AuditLog auditLog);
public final void sendToQueue(AuditLog auditLog) {
//send toQueue(auditLog)
}
public final void processAuditLog(String account, String action, String orderId) {
this.sendToQueue(buildDetails(buildAuditLog(account, action, orderId)));
}
}
创建AuditLog
代码如下(示例):
package com.example.designdemo.order.auditlog.pojo;
import java.util.Date;
/**• @Author: zhiwei Liao
• @Date: 2022/9/26 21:29
• @Description:
*/
public class AuditLog {
private String account;
private String action;
private Date date;
private String orderId;
private Object details; //订单创建需要有相关产品信息;
// 订单支付需要有相关产品信息以及支付方式和支付金额。
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getAction() {
return action;
}
public void setAction(String action) {
this.action = action;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public String getOrderId() {
return orderId;
}
public void setOrderId(String orderId) {
this.orderId = orderId;
}
public Object getDetails() {
return details;
}
public void setDetails(Object details) {
this.details = details;
}
@Override
public String toString() {
return “AuditLog{” +
“account='” + account + ‘’’ +
“, action='” + action + ‘’’ +
“, date=” + date +
“, orderId='” + orderId + ‘’’ +
“, details=” + details +
‘}’;
}
}
创建LoginLogProcessor
代码如下(示例):
package com.example.designdemo.order.auditlog;
import com.example.designdemo.order.auditlog.pojo.AuditLog;
import org.springframework.stereotype.Component;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:
*/
@Component
public class LoginLogProcessor extends AbstractAuditLogProcessor{
@Override
protected AuditLog buildDetails(AuditLog auditLog) {
return auditLog;
}
}
创建OrderLogProcessor
代码如下(示例):
package com.example.designdemo.order.auditlog;
import com.example.designdemo.order.auditlog.pojo.AuditLog;
import org.springframework.stereotype.Component;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:
*/
@Component
public class OrderLogProcessor extends AbstractAuditLogProcessor{
@Override
protected AuditLog buildDetails(AuditLog auditLog) {
String orderId = auditLog.getOrderId();
String productDetails = "通过 orderId 获取";
auditLog.setDetails(productDetails);
System.out.println(auditLog);
return auditLog;
}
}
创建PayLogProcessor
代码如下(示例):
package com.example.designdemo.order.auditlog;
import com.example.designdemo.order.auditlog.pojo.AuditLog;
import org.springframework.stereotype.Component;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:
*/
@Component
public class PayLogProcessor extends AbstractAuditLogProcessor{
@Override
protected AuditLog buildDetails(AuditLog auditLog) {
String orderId = auditLog.getOrderId();
String allDetails = "通过 orderId 或者是参数 获取产品信息,金额,支付方式";
auditLog.setDetails(allDetails);
System.out.println(auditLog);
return auditLog;
}
}
创建Order
代码如下(示例):
package com.example.designdemo.order.pojo;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:状态转化的一个控制机。状态机:初始化状态;配置我们的所有状态之间的转化关系;一些持久化的工作(redis)。
*/
public class Order {
private Integer orderId;
private OrderState orderState;//订单状态
public Integer getOrderId() {
return orderId;
}
public void setOrderId(Integer orderId) {
this.orderId = orderId;
}
public OrderState getOrderState() {
return orderState;
}
public void setOrderState(OrderState orderState) {
this.orderState = orderState;
}
}
创建OrderState
代码如下(示例):
package com.example.designdemo.order.pojo;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:订单状态
*/
public enum OrderState {
ORDER_WAIT_PAY, // 待支付
ORDER_WAIT_SEND, // 待发货
ORDER_WAIT_RECEIVE, // 待收货
ORDER_FINISH; // 完成订单
}
创建OrderStateChangeAction
代码如下(示例):
package com.example.designdemo.order.pojo;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:订单状态操作
*/
public enum OrderStateChangeAction {
PAY_ORDER, // 支付操作
SEND_ORDER, // 发货操作
RECEIVE_ORDER; // 收货操作
}
创建OrderStateMachineConfig
代码如下(示例):
package com.example.designdemo.order.config;
import com.example.designdemo.order.pojo.Order;
import com.example.designdemo.order.pojo.OrderState;
import com.example.designdemo.order.pojo.OrderStateChangeAction;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.statemachine.StateMachineContext;
import org.springframework.statemachine.StateMachinePersist;
import org.springframework.statemachine.config.EnableStateMachine;
import org.springframework.statemachine.config.StateMachineConfigurerAdapter;
import org.springframework.statemachine.config.builders.StateMachineStateConfigurer;
import org.springframework.statemachine.config.builders.StateMachineTransitionConfigurer;
import org.springframework.statemachine.persist.DefaultStateMachinePersister;
import org.springframework.statemachine.support.DefaultStateMachineContext;
import java.util.EnumSet;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:
*/
@Configuration
@EnableStateMachine(name="orderStateMachine")
public class OrderStateMachineConfig extends StateMachineConfigurerAdapter<OrderState, OrderStateChangeAction> {
public void configure(StateMachineStateConfigurer<OrderState, OrderStateChangeAction> states) throws Exception {
states.withStates().initial(OrderState.ORDER_WAIT_PAY)
.states(EnumSet.allOf(OrderState.class));
}
public void configure(StateMachineTransitionConfigurer<OrderState,
OrderStateChangeAction> transitions) throws Exception {
transitions.withExternal().source(OrderState.ORDER_WAIT_PAY)
.target(OrderState.ORDER_WAIT_SEND)
.event(OrderStateChangeAction.PAY_ORDER)
.and()
.withExternal().source(OrderState.ORDER_WAIT_SEND)
.target(OrderState.ORDER_WAIT_RECEIVE)
.event(OrderStateChangeAction.SEND_ORDER)
.and()
.withExternal().source(OrderState.ORDER_WAIT_RECEIVE)
.target(OrderState.ORDER_FINISH)
.event(OrderStateChangeAction.RECEIVE_ORDER);
}
// 配置状态机持久化
@Bean
public DefaultStateMachinePersister machinePersister() {
return new DefaultStateMachinePersister<>(new StateMachinePersist<Object, Object, Order>() {
@Override
public void write(StateMachineContext<Object, Object> stateMachineContext, Order order) throws Exception {
//持久化操作。可以通过任何形式进行持久化。redis 、 mongodb、mysql,ecache
}
@Override
public StateMachineContext<Object, Object> read(Order order) throws Exception {
// 本来是应该从持久化组件里进行读取的。但是没做持久化
return new DefaultStateMachineContext(order.getOrderState(), null, null, null);
}
});
}
}
创建OrderStateListener
代码如下(示例):
package com.example.designdemo.order.listener;
import com.example.designdemo.order.pojo.Order;
import com.example.designdemo.order.pojo.OrderState;
import com.example.designdemo.order.pojo.OrderStateChangeAction;
import org.springframework.messaging.Message;
import org.springframework.statemachine.annotation.OnTransition;
import org.springframework.statemachine.annotation.WithStateMachine;
import org.springframework.stereotype.Component;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/26 21:29
* @Description:监听器是监听到 action 后进行状态的一个变更。
*/
@Component("orderStateListener")
@WithStateMachine(name="orderStateMachine")
public class OrderStateListener {
@OnTransition(source = "ORDER_WAIT_PAY", target = "ORDER_WAIT_SEND")
public boolean payToSend(Message<OrderStateChangeAction> message){
Order order = (Order) message.getHeaders().get("order");
order.setOrderState(OrderState.ORDER_WAIT_SEND);
return true;
}
@OnTransition(source = "ORDER_WAIT_SEND", target = "ORDER_WAIT_RECEIVE")
public boolean sendToReceive(Message<OrderStateChangeAction> message){
Order order = (Order) message.getHeaders().get("order");
order.setOrderState(OrderState.ORDER_WAIT_RECEIVE);
return true;
}
@OnTransition(source = "ORDER_WAIT_RECEIVE", target = "ORDER_FINISH")
public boolean receiveToFinish(Message<OrderStateChangeAction> message){
Order order = (Order) message.getHeaders().get("order");
order.setOrderState(OrderState.ORDER_FINISH);
return true;
}
}
创建StrategyFacade
代码如下(示例):
package com.example.designdemo.pay.facade;
import com.example.designdemo.pay.additionalDecorator.AddFuncDecorator;
import com.example.designdemo.pay.context.PayContext;
import com.example.designdemo.pay.factory.AddFuncFactory;
import com.example.designdemo.pay.factory.PayFactory;
import com.example.designdemo.pay.strategy.PayStrategy;
import com.example.designdemo.pay.factory.StrategyFactory;
import com.example.designdemo.pay.pojo.PayBody;
import com.example.designdemo.pay.strategyEnum.StrategyEnum;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 11:27
* @Description: 门面模式,最终只暴露门面即可,门面就是我们的超级封装
*/
public class StrategyFacade {
// 定义一个map,将对应关系提前初始化好。
// 双十一的时候,有大量的用户进行下单(千万级),就会造成千万级的pay接口的调用。
// 很可惜,这部分代码里边有两个 new 关键字(new PayContext(payStrategy) 和 new AddFuncDecorator)。
// 如果瞬时见。有几十万的并发进来,那么会创建几十万个 context对象和 addFunc对象,造成 年轻代的eden区的频繁对象创建
// 虽然说调用完就进行了对象的垃圾收集,但是这么多的访问对象进来会造成,minorgc。
// 1. 单例模式吗?PayContext创建是基于payStrategy,不止一种paycontext啊,用单例不行呀。 AddFuncDecorator 是基于PayContext
// 创建的,PayContext 不止一种,AddFuncDecorator 也不止一种。
// 2. 享元模式。享元模式是单例模式的一种思想升级。单例模式,针对的是同一种对象,没有任何不同的细节。而享元模式,针对多个对象。
// 多个对象:同一种class,但是里边的属性有些许不同。PayContext是同一种对象吧?是的; PayContext 是不是有细节上的不同呢?是的,
// payStrategy不同; 那么我们是否可以知道这个PayContext的种类数量呢?是的,目前有三种。 享元模式能够对这可控数量的有不同细节的
//同一种class对象进行共享,保证我们的程序不频繁的创建对象。
public static Boolean pay(PayBody payBody) {
//获取我们的 策略枚举
StrategyEnum strategyEnum = getStrategyEnum(payBody.getType());
if(strategyEnum == null) {
return false;
}
//获取我们的策略对象
PayStrategy payStrategy = StrategyFactory.getPayStrategy(strategyEnum);
//生成我们的策略上下文
PayContext context = PayFactory.getPayContext(payStrategy); // 享元模式解决高并发下频繁创建对象的问题
// 装饰一下 context,。立马多了一个功能
// 我看这行代码啊,就不顺眼。代理模式搞他。
AddFuncDecorator addFuncDecorator = (AddFuncDecorator) AddFuncFactory.getAddFunc(context); // 享元模式解决高并发下频繁创建对象的问题
//进行扣款
return addFuncDecorator.execute(payBody);
}
private static StrategyEnum getStrategyEnum(int type) {
switch (type) {
case 0:
return StrategyEnum.ZfbPayStrategy;
case 1:
return StrategyEnum.WxPayStrategy;
case 2:
return StrategyEnum.BankPayStrategy;
default:
return null;
}
}
}
创建AddFuncFactory
代码如下(示例):
package com.example.designdemo.pay.factory;
import com.example.designdemo.pay.additionalDecorator.AbstractAddFuncDecorator;
import com.example.designdemo.pay.additionalDecorator.AddFuncDecorator;
import com.example.designdemo.pay.context.PayContext;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 20:53
* @Description:
*/
public class AddFuncFactory {
// 工厂的目的是生产 AddFuncDecorator; 生产几个啊? 多个:享元
// key 应该是能够和 AbstractAddFuncDecorator 做成对应的东西。
// 这个map最多保存是三个对象。
public final static Map<PayContext, AbstractAddFuncDecorator> maps = new ConcurrentHashMap<>();
public static AbstractAddFuncDecorator getAddFunc(PayContext payContext) {
if(maps.get(payContext) == null) {
AddFuncDecorator addFuncDecorator = new AddFuncDecorator(payContext);
maps.put(payContext, addFuncDecorator);
}
return maps.get(payContext);
}
}
创建PayFactory
代码如下(示例):
package com.example.designdemo.pay.factory;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import com.example.designdemo.pay.context.PayContext;
import com.example.designdemo.pay.strategy.PayStrategy;
/**
* @author zhiweiLiao<zhiwei.liao @ sgs.com>
* @Description 享元模式解决高并发下频繁创建对象的问题
* @Date create in 2022/9/28 0028 13:57
*/
public class PayFactory {
public final static Map<PayStrategy, PayContext> maps = new ConcurrentHashMap<>();
public static PayContext getPayContext(PayStrategy payStrategy) {
if(maps.get(payStrategy) == null) {
PayContext payContext = new PayContext(payStrategy);
maps.put(payStrategy, payContext);
}
return maps.get(payStrategy);
}
}
创建StrategyFactory
代码如下(示例):
package com.example.designdemo.pay.factory;
import com.example.designdemo.pay.strategy.PayStrategy;
import com.example.designdemo.pay.strategyEnum.StrategyEnum;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 10:53
* @Description: 策略工厂 工厂类依靠策略枚举返回策略类 后面都不需要修改了,因为它是一个无状态的 使用饿汉单例模式创建
*/
public class StrategyFactory {
private static final Map<String, PayStrategy> strategyMaps = new ConcurrentHashMap();
public static PayStrategy getPayStrategy(StrategyEnum strategyEnum){
PayStrategy payStrategy = strategyMaps.get(strategyEnum.getValue());
try {
payStrategy = (PayStrategy) Class.forName(strategyEnum.getValue()).newInstance();
strategyMaps.put(strategyEnum.getValue(), payStrategy);
} catch (Exception e) {
//异常信息打印
}
return payStrategy;
}
}
创建AddFuncDecorator
代码如下(示例):
package com.example.designdemo.pay.additionalDecorator;
import com.example.designdemo.pay.context.AbstractPayContext;
import com.example.designdemo.pay.pojo.PayBody;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 20:53
* @Description:abstractPayContext 不是共享的,因为有的小伙伴选择 zfb 支付,有的小伙伴选择wx支付,等等。。。
*/
public class AddFuncDecorator extends AbstractAddFuncDecorator{
public AddFuncDecorator(AbstractPayContext abstractPayContext) {
super(abstractPayContext);
}
// 新活儿
@Override
public void additionalFunction(PayBody payBody) { // 共享的,跟支付策略没有任何关系
String product = payBody.getProduct();
// 从db里边获取 product的详细信息。
// 从配置中心(redis缓存)里获取产品的更新策略。
// 根据策略更新用户平台币 或(和) 发放红包。
System.out.println("更新平台币成功,发送红包到用户优惠券模块成功。");
}
@Override
public Boolean execute(PayBody payBody) { // 算共享的。共享的调用逻辑
Boolean result = super.execute(payBody); //老活儿
this.additionalFunction(payBody); // 新活儿. 新活儿的各种重试,失败补偿
return result;
}
}
创建AbstractAddFuncDecorator
代码如下(示例):
package com.example.designdemo.pay.additionalDecorator;
import com.example.designdemo.pay.context.AbstractPayContext;
import com.example.designdemo.pay.pojo.PayBody;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 20:53
* @Description:
*/
public abstract class AbstractAddFuncDecorator extends AbstractPayContext {
// 这是我们的装饰器类。专门干装修的。 专门添加新功能的(平台币,红包)
// 装饰的是谁啊? 我作为一个称职的装饰器,我必须得知道装饰的是谁,不然我咋干活儿啊。
private AbstractPayContext abstractPayContext = null;
public AbstractAddFuncDecorator(AbstractPayContext abstractPayContext) {
this.abstractPayContext = abstractPayContext;
}
// 开始干活儿
//1. 老活儿。 支付。但是我又不能修改支付代码,也不能修改支付逻辑。
@Override
public Boolean execute(PayBody payBody) {
return abstractPayContext.execute(payBody);
}
//2. 老活儿不合适,没你装饰器照样能execute。 新活儿:平台币,红包)
public abstract void additionalFunction(PayBody payBody);
}
创建StrategyEnum
代码如下(示例):
package com.example.designdemo.pay.strategyEnum;
/**
* @Author: zhiwei Liao
* @Date: 2022/9/25 10:56
* @Description: 准备使用反射
*/
public enum StrategyEnum {
ZfbPayStrategy("com.example.designdemo.pay.strategy.ZfbPayStrategy"),
WxPayStrategy("com.example.designdemo.pay.strategy.WxPayStrategy"),
BankPayStrategy("com.example.designdemo.pay.strategy.BankPayStrategy");
String value = "";
StrategyEnum(String value){
this.value = value;
}
public String getValue(){
return this.value;
}
}