提交threadlocal讲解

.idea/libraries/Maven__com_google_guava_guava_18_0.xml

+<component name="libraryTable">
+  <library name="Maven: com.google.guava:guava:18.0">
+    <CLASSES>
+      <root url="jar://$MAVEN_REPOSITORY$/com/google/guava/guava/18.0/guava-18.0.jar!/" />
+    </CLASSES>
+    <JAVADOC>
+      <root url="jar://$MAVEN_REPOSITORY$/com/google/guava/guava/18.0/guava-18.0-javadoc.jar!/" />
+    </JAVADOC>
+    <SOURCES>
+      <root url="jar://$MAVEN_REPOSITORY$/com/google/guava/guava/18.0/guava-18.0-sources.jar!/" />
+    </SOURCES>
+  </library>
+</component>
\ No newline at end of file

README.md

@@ -92,7 +92,33 @@ redis的数量不是库存,他的作用仅仅只是为了阻挡多余的请求
 1.具体我会有时间更新关于redis的知识
 
 ### <font color=#0099ff size=3 >15.rabbitmq如何做到消息不重复不丢失即使服务器重启？</font><br>
-1.exchange持久化2.queue持久化3.发送消息设置MessageDeliveryMode.persisent这个也是默认的行为4.手动确认
 
+1.exchange持久化2.queue持久化3.发送消息设置MessageDeliveryMode.persisent这个也是默认的行为4.手动确认
 
- 
\ No newline at end of file
+### <font color=#0099ff size=3 >15.为什么threadlocal存储user对象，原理？？</font><br>
+
+![整体流程](http://i2.bvimg.com/601558/3293e36cc2c7e303.png)
+
+1.并发编程中重要的问题就是数据共享，当你在一个线程中改变任意属性时，所有的线程都会因此受到影响，同时会看到第一个线程修改后的值<br>
+有时我们希望如此，比如：多个线程增大或减小同一个计数器变量<br>
+但是，有时我们希望确保每个线程，只能工作在它自己的线程实例的拷贝上，同时不会影响其他线程的数据<br>
+
+举例： 举个例子，想象你在开发一个电子商务应用，你需要为每一个控制器处理的顾客请求，生成一个唯一的事务ID，同时将其传到管理器或DAO的业务方法中，以便记录日志。一种方案是将事务ID作为一个参数，传到所有的业务方法中。但这并不是一个好的方案，它会使代码变得冗余。
+    
+    你可以使用ThreadLocal类型的变量解决这个问题。首先在控制器或者任意一个预处理器拦截器中生成一个事务ID
+    然后在ThreadLocal中 设置事务ID，最后，不论这个控制器调用什么方法，都能从threadlocal中获取事务ID
+    而且这个应用的控制器可以同时处理多个请求，
+    同时在框架 层面，因为每一个请求都是在一个单独的线程中处理的，所以事务ID对于每一个线程都是唯一的，而且可以从所有线程的执行路径获取
+运行结果可以看出每个线程都在维护自己的变量：
+ Starting Thread: 0 : Fri Sep 21 23:05:34 CST 2018<br>
+ Starting Thread: 2 : Fri Sep 21 23:05:34 CST 2018<br>
+ Starting Thread: 1 : Fri Jan 02 05:36:17 CST 1970<br>
+ Thread Finished: 1 : Fri Jan 02 05:36:17 CST 1970<br>
+ Thread Finished: 0 : Fri Sep 21 23:05:34 CST 2018<br>
+ Thread Finished: 2 : Fri Sep 21 23:05:34 CST 2018<br>
+ 
+ 局部线程通常使用在这样的情况下，当你有一些对象并不满足线程安全，但是你想避免在使用synchronized关键字<br>
+ 块时产生的同步访问，那么，让每个线程拥有它自己的对象实例<br>
+ 注意：局部变量是同步或局部线程的一个好的替代，它总是能够保证线程安全。唯一可能限制你这样做的是你的应用设计约束<br>
+ 
+ 所以设计threadlocal存储user不会对对象产生影响，每次进来一个请求都会产生自身的线程变量来存储
\ No newline at end of file

miaosha.iml

@@ -49,6 +49,7 @@
     <orderEntry type="library" name="Maven: org.springframework:spring-context:4.3.12.RELEASE" level="project" />
     <orderEntry type="library" name="Maven: org.springframework:spring-webmvc:4.3.12.RELEASE" level="project" />
     <orderEntry type="library" name="Maven: org.springframework:spring-expression:4.3.12.RELEASE" level="project" />
+    <orderEntry type="library" name="Maven: com.google.guava:guava:18.0" level="project" />
     <orderEntry type="library" name="Maven: org.springframework.boot:spring-boot-starter-thymeleaf:1.5.8.RELEASE" level="project" />
     <orderEntry type="library" name="Maven: org.thymeleaf:thymeleaf-spring4:2.1.5.RELEASE" level="project" />
     <orderEntry type="library" name="Maven: org.thymeleaf:thymeleaf:2.1.5.RELEASE" level="project" />

pom.xml

@@ -24,7 +24,11 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-web</artifactId>
 		</dependency>
-
+		<dependency>
+			<groupId>com.google.guava</groupId>
+			<artifactId>guava</artifactId>
+			<version>18.0</version>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-thymeleaf</artifactId>

src/main/java/com/geekq/miaosha/DemoTask.java

+package com.geekq.miaosha;
+
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class DemoTask implements Runnable
+{
+    // Atomic integer containing the next thread ID to be assigned
+    private static final AtomicInteger nextId   = new AtomicInteger(0);
+
+    // Thread local variable containing each thread's ID
+    private static final ThreadLocal<Integer> threadId = new ThreadLocal<Integer>()
+    {
+        @Override
+        protected Integer initialValue()
+        {
+            return nextId.getAndIncrement();
+        }
+    };
+
+    // Returns the current thread's unique ID, assigning it if necessary
+    public int getThreadId()
+    {
+        return threadId.get();
+    }
+    // Returns the current thread's starting timestamp
+    private static final ThreadLocal<Date> startDate = new ThreadLocal<Date>()
+    {
+        protected Date initialValue()
+        {
+            if(threadId.get()==1){
+                return new Date(77777777L);
+            }
+            return new Date();
+        }
+    };
+
+
+
+    @Override
+    public void run()
+    {
+        System.out.printf("Starting Thread: %s : %s\n", getThreadId(), startDate.get());
+        try
+        {
+            TimeUnit.SECONDS.sleep((int) Math.rint(Math.random() * 10));
+        } catch (InterruptedException e)
+        {
+            e.printStackTrace();
+        }
+        System.out.printf("Thread Finished: %s : %s\n", getThreadId(), startDate.get());
+    }
+}
\ No newline at end of file

src/main/java/com/geekq/miaosha/Test.java

+package com.geekq.miaosha;
+
+public class Test {
+    public static void main(String[] args) {
+        DemoTask demoTask = new DemoTask();
+        DemoTask demoTask1 = new DemoTask();
+        DemoTask demoTask2 = new DemoTask();
+        Thread t = new Thread(demoTask);
+            t.start();
+        new Thread(demoTask).start();
+        new Thread(demoTask2).start();
+
+
+    }
+}

src/main/java/com/geekq/miaosha/config/UserArgumentResolver.java

 package com.geekq.miaosha.config;
 
+import com.geekq.miaosha.access.UserContext;
 import com.geekq.miaosha.domain.MiaoshaUser;
 import com.geekq.miaosha.service.MiaoShaUserService;
-import org.apache.commons.lang3.StringUtils;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.MethodParameter;
 import org.springframework.stereotype.Service;
@@ -13,7 +13,6 @@ import org.springframework.web.method.support.ModelAndViewContainer;
 
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletRequest;
-import javax.servlet.http.HttpServletResponse;
 
 @Service
 public class UserArgumentResolver implements HandlerMethodArgumentResolver {
@@ -28,16 +27,18 @@ public class UserArgumentResolver implements HandlerMethodArgumentResolver {
 
     @Override
     public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest webRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {
-        HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
-        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
-
-        String paramToken = request.getParameter(MiaoShaUserService.COOKIE_NAME_TOKEN);
-        String cookieToken = getCookieValue(request, MiaoShaUserService.COOKIE_NAME_TOKEN);
-        if(StringUtils.isEmpty(cookieToken) && StringUtils.isEmpty(paramToken)) {
-            return null;
-        }
-        String token = StringUtils.isEmpty(paramToken)?cookieToken:paramToken;
-        return userService.getByToken(response, token);
+//        HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
+//        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
+//
+//        String paramToken = request.getParameter(MiaoShaUserService.COOKIE_NAME_TOKEN);
+//        String cookieToken = getCookieValue(request, MiaoShaUserService.COOKIE_NAME_TOKEN);
+//        if(StringUtils.isEmpty(cookieToken) && StringUtils.isEmpty(paramToken)) {
+//            return null;
+//        }
+//        String token = StringUtils.isEmpty(paramToken)?cookieToken:paramToken;
+//        return userService.getByToken(response, token);
+        //threadlocal 存储线程副本 保证线程不冲突
+        return UserContext.getUser();
     }
 
     private String getCookieValue(HttpServletRequest request, String cookiName) {

src/main/java/com/geekq/miaosha/controller/MiaoshaController.java

@@ -66,12 +66,22 @@ public class MiaoshaController implements InitializingBean {
 			return Result.error(CodeMsg.SESSION_ERROR);
 		}
 
+
 		//验证path
 		boolean check = miaoshaService.checkPath(user, goodsId, path);
 		if(!check){
 			return Result.error(CodeMsg.REQUEST_ILLEGAL);
 		}
 
+//		//使用RateLimiter 限流
+//		RateLimiter rateLimiter = RateLimiter.create(10);
+//		//判断能否在1秒内得到令牌，如果不能则立即返回false，不会阻塞程序
+//		if (!rateLimiter.tryAcquire(1000, TimeUnit.MILLISECONDS)) {
+//			System.out.println("短期无法获取令牌，真不幸，排队也瞎排");
+//			return Result.error(CodeMsg.MIAOSHA_FAIL);
+//
+//		}
+
 		//是否已经秒杀到
 		MiaoshaOrder order = orderService.getMiaoshaOrderByUserIdGoodsId(user.getId(), goodsId);
 		if(order!=null){

src/main/java/com/geekq/miaosha/controller/RateLimiterController.java

+package com.geekq.miaosha.controller;
+
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.RequestMapping;
+
+@Controller
+@RequestMapping("/ratelimiter")
+public class RateLimiterController {
+
+}