前言
在应用框架日常开发中须要在controller中进行一些异步操作缩小申请工夫，然而发现在应用@Anysc注解后会呈现Request对象无奈获取的状况，本文就此状况给出残缺的解决方案
起因剖析
- @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
- 在应用springboot的自定带的线程共享后，代码如下，Request不为null，然而偶发的其中body/head/urlparam内容呈现获取不到的状况，是因为异步工作在未执行结束的状况下，主线程曾经返回，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
- 启动类增加@EnableAsync注解
- 标记@Async的异步办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：零碎中所有Request获取须要对立从CommonUtil指定起源，例如token鉴权等
自定义request过滤器
通过自定义过滤器对Request的内容进行备份保留，主线程完结时Request革除完结不会影响到子线程的相应参数的获取，也实用于减少拦截器/过滤器后body参数无奈反复获取的问题。须要留神的是对header参数解决时key要疏忽大小写
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); } //获取申请中的流如何，将取出来的字符串，再次转换成流，而后把它放入到新request对象中。 // 在chain.doFiler办法中传递新的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; }}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); }}自定义工作执行器
用于拦挡异步工作执行，在工作执前对立进行Request共享操作，且能够定义多个，不影响原有的异步工作代码
public class CustomTaskDecorator implements TaskDecorator { @Override public Runnable decorate(Runnable runnable) { ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes(); HttpServletRequest request = requestAttributes.getRequest(); System.out.println("异步工作共享request"); return () -> { try { CommonUtil.shareRequest(request); runnable.run(); } finally { CommonUtil.remove(); } }; }}@Configurationpublic 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); // 减少 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挡的工作执行器即可
@PostMapping("/testAsync") @ResponseBody public Object testAsync(@RequestBody Map<String, Object> params) throws Exception{ Result result = Result.okResult(); asyncUtil.executeAsync(); return result; }@Componentpublic class AsyncUtil { @Async("shareTaskExecutor") public void executeAsync () throws InterruptedException { System.out.println("开始执行executeAsync"); Thread.sleep(3000); System.out.println("完结执行executeAsync"); }}