线程封闭 线程封闭当访问共享数据时，通常是要使用同步。如果要避免使用同步，就是不提供共享数据。如果仅在单线程中访问数据，就不需要同步，这种技术就叫做线程封闭，它是实现线程安全最简单的方式之一。当某个对象封闭在一个线程当中时将自动实现线程安全性，即使被封闭的对象本身它并不是安全的，实现线程主要有三种方式。实现线程封闭的三种方式：1、Ad-hoc线程封闭：程序控制实现，最糟糕，忽略2、堆栈封闭：局部变量，无并发问题：栈封闭简单理解就是通过局部变量来实现线程封闭，多个线程访问对象的同一个方法，方法内部的局部变量会拷贝到每个线程的线程栈当中，只有当前线程才能访问到，互不干扰。所以局部变量是不被多个线程所共享的。尽量少用全局变量(不是全局常量)。3、ThreadLocal线程封闭：特别好的封闭方法。维护线程封闭一种更规范的方法就是使用ThreadLocal。ThreadLocal底层是一个map，可以就是线程名字，value就是我们封装的对象。ThreadLocal提供get、set方法为每个使用该变量的线程都存有一份独立的副本，因此get总是返回的是当前线程在调用set时设置的值。ThreadLocal一般用于防止对可变的单实例变量或者全局变量进行共享。ThreadLocal使用：代码示例1、自定义ThreadLoca工具package com.yanxizhu.demo.concurrency.DemoThrodLocal.ThreadLock; /** * @description: 使用ThrodLock的线程封闭，实现在一个线程种数据共享 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 22:56 * @version: 1.0 */ public class MyThroldLock { private final static ThreadLocal<Long> requestholder = new ThreadLocal<>(); //用ThreadLock提供的set方法，向ThreadLock中放入共享数据id //一般在实际接口处理前调用 public static void add(Long id) { requestholder.set(id); } //用ThreadLock提供的get方法获取ThreadLock中共享的数据 public static Long get() { return requestholder.get(); } //用ThreadLock提供的remove方法移除共享数据，不然容易导致内存溢出 //一般在接口真正处理完后调用 public static void remove() { requestholder.remove(); } }2、自定义过滤器Filterpackage com.yanxizhu.demo.concurrency.DemoThrodLocal.filter; import com.yanxizhu.demo.concurrency.DemoThrodLocal.ThreadLock.MyThroldLock; import lombok.extern.slf4j.Slf4j; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * @description: 自定一自己的filter，实现filter接口，注意是servlet中的 * 说明： * Servlet中的过滤器Filter是实现了javax.servlet.Filter接口的服务器端程序， * 主要的用途是设置字符集、控制权限、控制转向、做一些业务逻辑判断等。其工作原理是， * 只要你在web.xml文件配置好要拦截的客户端请求，它都会帮你拦截到请求， * 此时你就可以对请求或响应(Request、Response)统一设置编码，简化操作； * 同时还可进行逻辑判断，如用户是否已经登陆、有没有权限访问该页面等等工作。 * 它是随你的web应用启动而启动的，只初始化一次，以后就可以拦截相关请求，只有当你的web应用停止或重新部署的时候才销毁。 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 23:02 * @version: 1.0 */ @Slf4j public class HttpFilter implements Filter { //初始化的 public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { //一般需要强转成HttpServletRequest、HttpServletResponse，这样才能直接获取用户浏览器访问时携带信息 //比如获取用户session中的用户信息 HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; //一般登录会将用户信息写入session,这里只是演示一下 // String userName = (String) request.getSession().getAttribute("userName"); log.info("do filter，线程id {},请求地址{}", Thread.currentThread().getId(), request.getServletPath()); //通过向ThreadLock添加共享值 MyThroldLock.add(Thread.currentThread().getId()); // 所有处理完后，记得执行下面，不然不会往下执行 filterChain.doFilter(servletRequest, servletResponse); } //销毁时的 public void destroy() { } }注册自定义过滤器HttpFilterpackage com.yanxizhu.demo.concurrency.DemoThrodLocal.filter; import org.springframework.boot.web.servlet.FilterRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; /** * @description: 将自定义的filter添加到spring拦截器中 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 23:37 * @version: 1.0 */ @Configuration public class MyFilterConfig { @Bean public FilterRegistrationBean httpFilter() { FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(); filterRegistrationBean.setFilter(new HttpFilter()); filterRegistrationBean.addUrlPatterns("/demo/*"); return filterRegistrationBean; } }3、自定义拦截器HandlerInterceptorpackage com.yanxizhu.demo.concurrency.DemoThrodLocal.interceptor; import com.yanxizhu.demo.concurrency.DemoThrodLocal.ThreadLock.MyThroldLock; import lombok.extern.slf4j.Slf4j; import org.springframework.context.annotation.Configuration; import org.springframework.stereotype.Component; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.handler.HandlerInterceptorAdapter; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @description: 自定义HandlerInerceptor * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 22:28 * @version: 1.0 */ @Slf4j @Component public class MyHandlerInterceptor implements HandlerInterceptor { //接口处理之前 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { log.info("进入controller之前的preHanler方法。。。。"); return true; } public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { log.info("这个是干嘛的呢。。。"); } //接口处理之后 public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { log.info("之后的方法。。。。afterCompletion,MyThroldLock.remove()"); MyThroldLock.remove(); return; } }注册自定义拦截器MyHandlerInterceptorpackage com.yanxizhu.demo.concurrency.DemoThrodLocal.interceptor; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; /** * @description: 自定义WebMVCConfig * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 22:31 * @version: 1.0 */ @Configuration public class MyWebMvcConfigurerAdapter implements WebMvcConfigurer { @Autowired MyHandlerInterceptor myHandlerInterceptor; public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(myHandlerInterceptor).addPathPatterns("/**"); } }4、编写Controller测试ThreadLock的使用package com.yanxizhu.demo.concurrency.DemoThrodLocal.controller; import com.yanxizhu.demo.concurrency.DemoThrodLocal.ThreadLock.MyThroldLock; import lombok.extern.slf4j.Slf4j; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * @description: HandlerInterceptor 拦截器测试 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/4/22 22:25 * @version: 1.0 */ @RestController @RequestMapping("/demo") @Slf4j public class ThreadLockController { @GetMapping("/myHandlerInterceptor") public String myHandlerInterceptorTest() { log.info("进入Controoler方法种。。。。。。"); return "My HandlerInterceptor....,共享ThreadLock的变量为："+MyThroldLock.get(); } }测试请求地址http://127.0.0.1:8080/demo/myHandlerInterceptor页面输出结果：My HandlerInterceptor....,共享ThreadLock的变量为：46IDEA控制台输出结果：do filter，线程id 50,请求地址/demo/myHandlerInterceptor 进入controller之前的preHanler方法。。。。 进入Controoler方法种。。。。。。 这个是干嘛的呢。。。 之后的方法。。。。afterCompletion注意点注意过滤器Filter和拦截器HandlerInterceptor的区别及使用方式。可参考地址：https://blog.csdn.net/yb546822612/article/details/102950040https://blog.csdn.net/yb546822612/article/details/102950981

CompletableFuture异步编排 通过线程池性能稳定，也可以获取执行结果，并捕获异常。但是，在业务复杂情况下，一个异步调用可能会依赖于另一个异步调用的执行结果。因此我们可以使用completableFuture 异步编排方案。比如：一个业务场景，需要同时获取多个数据，如果同步线程挨个执行，则需要时间为所有线程执行时间的总和。如果我们使用异步线程执行，所需时间则为耗时最长那个异步线程的执行时间。如果多个异常线程之间还存在依赖关系，比如线程3需要线程1的执行结果，线程6依赖线程3、线程2，那这个问题怎么解决呢。那就可以使用completableFuture 异步编排方案实现。注意：completableFuture 是jdk1.8之后添加的一个功能。CompletableFuture接口:public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {public interface Future<V> {以前用到的FutureTask就是用到的Future可以得到返回结果public class FutureTask<V> implements RunnableFuture<V> {public interface RunnableFuture<V> extends Runnable, Future<V> { /** * Sets this Future to the result of its computation * unless it has been cancelled. */ void run(); }Future可以得到返回结果CompletableFuture随便一个方法，都接受一个Function public <U> CompletableFuture<U> applyToEither( CompletionStage<? extends T> other, Function<? super T, U> fn) { return orApplyStage(null, other, fn); }@FunctionalInterface public interface Function<T, R> {Function是一个@FunctionalInterface，所以对Lambda使用要熟悉。CompletableFuture异步编排问题多个异步线程远程调用会导致丢失请求头，原因是多个线程，通过拦截器不能获取其它线程的请求的heard信息。解决方案：每个线程共享自己的requestAttributes。自定义feign拦截器：import feign.RequestInterceptor; import feign.RequestTemplate; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.context.request.RequestContextHolder; import org.springframework.web.context.request.ServletRequestAttributes; import javax.servlet.http.HttpServletRequest; /** * @description: TODO * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/3/10 23:03 * @version: 1.0 */ @Configuration public class FamilyFegin { @Bean(name ="requestInterceptor") public RequestInterceptor requestInterceptor(){ return new RequestInterceptor() { @Override public void apply(RequestTemplate requestTemplate) { //RequestContextHolder拿到刚请求来的数据 ServletRequestAttributes requestAttributes = (ServletRequestAttributes)RequestContextHolder.getRequestAttributes(); System.out.println("requestAttributes线程"+Thread.currentThread().getId()); HttpServletRequest request = requestAttributes.getRequest(); System.out.println("调用feign之前"); if(request != null){ //同步请求头数据 String cookie = request.getHeader("Cookie");//老数据 //给新请求同步老请求的cookie requestTemplate.header("Cookie", cookie); } } }; } }web配置：因为需要拦截器生效import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; /** * @description: WEB配置 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/3/10 22:40 * @version: 1.0 */ public class FamilyWebConfig implements WebMvcConfigurer { @Autowired LoginUserInterceptor loginUserInterceptor; @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(loginUserInterceptor).addPathPatterns("/**"); } }CompletableFuture异步编排import org.springframework.web.context.request.RequestContextHolder; import org.springframework.web.context.request.ServletRequestAttributes; import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * @description: CompletableFuture异步编排 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/3/10 23:32 * @version: 1.0 */ public class MyCompletableFuture { public static ExecutorService executorService = Executors.newFixedThreadPool(10); public void myOpenFeign() throws ExecutionException, InterruptedException { System.out.println("主线程0"); //远程调用存在丢失请求头的问题，因为不在同一线程，导致自定义拦截器不能获取head信息。 //解决丢失请求头方案： ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes(); //第一个异步任务 CompletableFuture<Void> oneFuture = CompletableFuture.runAsync(() -> { System.out.println("辅线程1"); //每个线程都共享一下自己的requestAttributes RequestContextHolder.setRequestAttributes(requestAttributes); //异步线程远程调用，业务1 //异步线程调用业务代码 }, executorService); //第二个异步任务 CompletableFuture<Void> twoFuture = CompletableFuture.runAsync(() -> { System.out.println("辅线程2"); //每个线程都共享一下自己的requestAttributes RequestContextHolder.setRequestAttributes(requestAttributes); //异步线程远程调用，业务2 //异步线程调用业务代码 }, executorService); CompletableFuture.allOf(oneFuture, twoFuture).get(); } }以上就是解决CompletableFuture异步编排，异步多线程引起的远程调用请求丢失解决方案。代码中共享requestAttributes原因ThreadLocal数据：ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();RequestContextHolder主线程不一样获取的数据不一样，如下：import javax.faces.context.FacesContext; import org.springframework.core.NamedInheritableThreadLocal; import org.springframework.core.NamedThreadLocal; import org.springframework.lang.Nullable; import org.springframework.util.ClassUtils; public abstract class RequestContextHolder { private static final boolean jsfPresent = ClassUtils.isPresent("javax.faces.context.FacesContext", RequestContextHolder.class.getClassLoader()); private static final ThreadLocal<RequestAttributes> requestAttributesHolder = new NamedThreadLocal("Request attributes"); private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder = new NamedInheritableThreadLocal("Request context"); public RequestContextHolder() { }

Springboot拦截器配置 Springboot拦截器配置1、拦截器配置，主要实现HandlerInterceptor接口import org.springframework.stereotype.Component; import org.springframework.web.servlet.HandlerInterceptor; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @description: 拦截器，配合FamilyWebConfig 配置使用 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/3/10 22:36 * @version: 1.0 */ @Component public class LoginUserInterceptor implements HandlerInterceptor { public static ThreadLocal<Object> objUser = new ThreadLocal<>(); @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { Object loginusr = request.getSession().getAttribute("LOGIN_USR"); if(loginusr != null){ objUser.set(loginusr); //登录了才能访问 return true; }else{ //没登录，跳转去登录 return false; } } } 由于拦截器需要配合web配置使用，因此创建web配置。2、web配置主要实现WebMvcConfigurer接口import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; /** * @description: WEB配置 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/3/10 22:40 * @version: 1.0 */ public class FamilyWebConfig implements WebMvcConfigurer { @Autowired LoginUserInterceptor loginUserInterceptor; @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(loginUserInterceptor).addPathPatterns("/**"); } }