前言

在使用框架日常开发中需要在controller中进行一些异步操作减少请求时间，但是发现在使用@Anysc注解后会出现Request对象无法获取的情况，本文就此情况给出完整的解决方案

原因分析

@Anysc注解会开启一个新的线程，主线程的Request和子线程是不共享的，所以获取为null

在使用springboot的自定带的线程共享后，代码如下，Request不为null，但是偶发的其中body/head/urlparam内容出现获取不到的情况，是因为异步任务在未执行完毕的情况下，主线程已经返回，拷贝共享的Request对象数据被清空

ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
//设置子线程共享
RequestContextHolder.setRequestAttributes(servletRequestAttributes, true);
HttpServletRequest request = servletRequestAttributes.getRequest();

解决方案

前置条件
        启动类添加@EnableAsync注解
        标记@Async的异步方法不能和调用者在同一个class中

pom配置

<!-- 阿里线程共享 --><dependency><groupId>com.alibaba</groupId><artifactId>transmittable-thread-local</artifactId><version>2.11.0</version></dependency>

requrest共享
通过TransmittableThreadLocal对象进行线程对象共享

public class CommonUtil {public static TransmittableThreadLocal<HttpServletRequest> requestTransmittableThreadLocal = new TransmittableThreadLocal<HttpServletRequest>();public static void shareRequest(HttpServletRequest request){requestTransmittableThreadLocal.set(request);}public static HttpServletRequest getRequest(){HttpServletRequest request = requestTransmittableThreadLocal.get();if(request!=null){return requestTransmittableThreadLocal.get();}else{ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();if(requestAttributes!=null){return  requestAttributes.getRequest();}else{return  null;}}}public static void remove(){requestTransmittableThreadLocal.remove();}
}

注：系统中所有Request获取需要统一从CommonUtil指定来源，例如token鉴权等

自定义request过滤器

通过自定义过滤器对Request的内容进行备份保存，主线程结束时Request清除结束不会影响到子线程的相应参数的获取，也适用于增加拦截器/过滤器后body参数无法重复获取的问题。需要注意的是对header参数处理时key要忽略大小写

public class HttpServletRequestReplacedFilter implements Filter, Ordered {@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {ServletRequest requestWrapper = null;if (request instanceof HttpServletRequest) {requestWrapper = new RequestWrapper((HttpServletRequest) request);}//获取请求中的流如何，将取出来的字符串，再次转换成流，然后把它放入到新request对象中。// 在chain.doFiler方法中传递新的request对象if (requestWrapper == null) {chain.doFilter(request, response);} else {chain.doFilter(requestWrapper, response);}}@Overridepublic void init(FilterConfig arg0) throws ServletException {}@Overridepublic int getOrder() {return 10;}
}public class RequestWrapper extends HttpServletRequestWrapper{private final byte[] body;private final HashMap<String,String> headMap;private final HashMap<String,String> requestParamMap;public RequestWrapper(HttpServletRequest request) throws IOException {super(request);body = CommonUtil.getBodyString(request).getBytes(Charset.forName("UTF-8"));headMap = new HashMap();Enumeration<String> headNameList = request.getHeaderNames();while (headNameList.hasMoreElements()){String key = headNameList.nextElement();headMap.put(key.toLowerCase(),request.getHeader(key));}requestParamMap = new HashMap<>();Enumeration<String> parameterNameList = request.getParameterNames();while (parameterNameList.hasMoreElements()){String key = parameterNameList.nextElement();requestParamMap.put(key,request.getParameter(key));}}@Overridepublic BufferedReader getReader() throws IOException {return new BufferedReader(new InputStreamReader(getInputStream()));}@Overridepublic ServletInputStream getInputStream() throws IOException {final ByteArrayInputStream bais = new ByteArrayInputStream(body);return new ServletInputStream() {@Overridepublic int read() throws IOException {return bais.read();}@Overridepublic boolean isFinished() {return false;}@Overridepublic boolean isReady() {return false;}@Overridepublic void setReadListener(ReadListener readListener) {}};}@Overridepublic String getHeader(String name) {return headMap.get(name.toLowerCase());}@Overridepublic String getParameter(String name) {return requestParamMap.get(name);}
}

自定义任务执行器

用于拦截异步任务执行，在任务执前统一进行Request共享操作，且可以定义多个，不影响原有的异步任务代码

public class CustomTaskDecorator implements TaskDecorator {@Overridepublic Runnable decorate(Runnable runnable) {ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();HttpServletRequest request = requestAttributes.getRequest();System.out.println("异步任务共享request");return () -> {try {CommonUtil.shareRequest(request);runnable.run();} finally {CommonUtil.remove();}};}
}@Configuration
public class TaskExecutorConfig {@Bean()public Executor taskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(10);executor.setMaxPoolSize(20);executor.setQueueCapacity(200);executor.setKeepAliveSeconds(60);executor.setThreadNamePrefix("taskExecutor-");executor.setAwaitTerminationSeconds(60);executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}@Bean("shareTaskExecutor")public Executor hpTaskExecutor() {ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();executor.setCorePoolSize(10);executor.setMaxPoolSize(20);executor.setQueueCapacity(200);executor.setKeepAliveSeconds(60);executor.setThreadNamePrefix("shareTaskExecutor-");executor.setWaitForTasksToCompleteOnShutdown(true);executor.setAwaitTerminationSeconds(60);// 增加 TaskDecorator 属性的配置executor.setTaskDecorator(new CustomTaskDecorator());executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());executor.initialize();return executor;}
}

调用示例

给@Anysc注解指定进行共享拦截的任务执行器即可

@PostMapping("/testAsync")@ResponseBodypublic Object testAsync(@RequestBody Map<String, Object> params) throws Exception{Result result = Result.okResult();asyncUtil.executeAsync();return result;}@Component
public class AsyncUtil {@Async("shareTaskExecutor")public void executeAsync () throws InterruptedException {System.out.println("开始执行executeAsync");Thread.sleep(3000);System.out.println("结束执行executeAsync");}
}