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
com.alibaba
transmittable-thread-local
2.11.0
requrest共享
通过TransmittableThreadLocal对象进行线程对象共享
public class CommonUtil {
public static TransmittableThreadLocal requestTransmittableThreadLocal = new TransmittableThreadLocal();
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 {
@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;
}
}public class RequestWrapper extends HttpServletRequestWrapper{
private final byte[] body;
private final HashMap headMap;
private final HashMap requestParamMap;
public RequestWrapper(HttpServletRequest request) throws IOException {
super(request);
body = CommonUtil.getBodyString(request).getBytes(Charset.forName("UTF-8"));
headMap = new HashMap();
Enumeration headNameList = request.getHeaderNames();
while (headNameList.hasMoreElements()){
String key = headNameList.nextElement();
headMap.put(key.toLowerCase(),request.getHeader(key));
}
requestParamMap = new HashMap<>();
Enumeration 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
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();
}
};
}
}@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")
@ResponseBody
public Object testAsync(@RequestBody Map 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");
}
}