feat:上传备忘录模式例子

README.md

@@ -42,7 +42,7 @@
    * ENUM模式(最安全) 已完成
    * 静态内部类模式  已完成
 
-15.备忘录模式 - 整理中
+15.备忘录模式 - 已完成
 
 16.组合模式 - 整理中
 

src/main/com/mxy/design/memento/Memento.java

@@ -0,0 +1,19 @@
+package com.mxy.design.memento;
+
+public class Memento {
+
+    private String state;
+
+    public Memento(String state){
+        this.state = state;
+    }
+
+    public String getState() {
+        return state;
+    }
+
+    public void setState(String state) {
+        this.state = state;
+    }
+
+}

src/main/com/mxy/design/memento/OrderState.java

@@ -0,0 +1,31 @@
+package com.mxy.design.memento;
+
+import java.util.Stack;
+
+/**
+ * 订单状态
+ */
+public class OrderState {
+
+    /**
+     * 利用LIFO 后进先出
+     */
+    private Stack<String> stateList = new Stack<>();
+
+    public Stack<String> getStateList() {
+        return stateList;
+    }
+
+    public void setStateList(Stack<String> stateList) {
+        this.stateList = stateList;
+    }
+
+    /**
+     * 存储当前添加的状态
+     * @param memento
+     */
+    public void restoreMemento(Memento memento){
+         this.stateList.add(memento.getState());
+    }
+
+}

src/main/com/mxy/design/memento/OrderStateProcess.java

@@ -0,0 +1,17 @@
+package com.mxy.design.memento;
+
+/**
+ * 订单流程处理
+ */
+public class OrderStateProcess {
+
+    private Memento memento;
+
+    public OrderStateProcess(Memento memento) {
+        this.memento = memento;
+    }
+
+    public Memento rollbackLastState() {
+        return memento;
+    }
+}

src/test/com/mxy/design/memento/MementoTest.java

@@ -0,0 +1,60 @@
+package com.mxy.design.memento;
+
+import org.junit.Test;
+
+import java.util.Random;
+
+/**
+ * 备忘录模式：备忘录模式可以使系统恢复到某一历史时期的状态，又称标记模式
+ * 场景：模拟下单流程，出现异常回滚到上个状态。
+ */
+public class MementoTest {
+
+    @Test
+    public void logicTest() {
+
+        Memento memento1 = new Memento("待下单");
+        OrderState state = new OrderState();
+        state.restoreMemento(memento1);
+        //赋值当前订单状态
+        OrderStateProcess orderStateProcess = new OrderStateProcess(memento1);
+
+        System.out.println("正在生成订单.....");
+        if (rollbackState(orderStateProcess)){
+            return;
+        }
+
+        Memento memento2 = new Memento("生成订单");
+        state.restoreMemento(memento2);
+
+        System.out.println("已生成订单准备支付");
+
+        orderStateProcess = new OrderStateProcess(memento2);
+        Memento memento3 = new Memento("待支付");
+        state.restoreMemento(memento3);
+
+
+        orderStateProcess = new OrderStateProcess(memento3);
+
+        System.out.println("正在支付.....");
+        if (rollbackState(orderStateProcess)){
+            return;
+        }
+
+        Memento memento4 = new Memento("已支付");
+        System.out.println("支付成功：当前订单状态："+memento4.getState());
+        state.restoreMemento(memento4);
+
+    }
+
+    private boolean rollbackState(OrderStateProcess orderStateProcess) {
+        //模拟场景 如果异常问题则回滚
+        if((new Random().nextBoolean())) {
+            orderStateProcess.rollbackLastState();
+            System.out.println("出现异常回滚到订单状态："+orderStateProcess.rollbackLastState().getState());
+            return true;
+        }
+        return false;
+    }
+
+}