百木园前言
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 {
@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<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
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<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\");
}
}
来源：https://www.cnblogs.com/yanpeng19940119/p/16122249.html
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