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
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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
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<!-- 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
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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
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public class HttpServletRequestReplacedFilter implements Filter, Ordered { @Override public void destroy() { } @Override public 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); } } @Override public void init(FilterConfig arg0) throws ServletException { } @Override public int getOrder() { return 10 ; } } |
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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)); } } @Override public BufferedReader getReader() throws IOException { return new BufferedReader( new InputStreamReader(getInputStream())); } @Override public ServletInputStream getInputStream() throws IOException { final ByteArrayInputStream bais = new ByteArrayInputStream(body); return new ServletInputStream() { @Override public int read() throws IOException { return bais.read(); } @Override public boolean isFinished() { return false ; } @Override public boolean isReady() { return false ; } @Override public void setReadListener(ReadListener readListener) { } }; } @Override public String getHeader(String name) { return headMap.get(name.toLowerCase()); } @Override public 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
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public class CustomTaskDecorator implements TaskDecorator { @Override public 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(); } }; } } |
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@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
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@PostMapping ( "/testAsync" ) @ResponseBody public Object testAsync( @RequestBody Map<String, Object> params) throws Exception{ Result result = Result.okResult(); asyncUtil.executeAsync(); return result; } |
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@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" ); } } |
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原文链接：https://blog.csdn.net/u013407099/article/details/124061950
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