SpringBoot詳細講解異步任務(wù)如何獲取HttpServletRequest

更新時間：2022年04月25日 11:35:34 作者：code2roc

在使用框架日常開發(fā)中需要在controller中進行一些異步操作減少請求時間，但是發(fā)現(xiàn)在使用@Anysc注解后會出現(xiàn)Request對象無法獲取的情況，本文就此情況給出完整的解決方案

原因分析

@Anysc注解會開啟一個新的線程，主線程的Request和子線程是不共享的，所以獲取為null
在使用springboot的自定帶的線程共享后，代碼如下，Request不為null，但是偶發(fā)的其中body/head/urlparam內(nèi)容出現(xiàn)獲取不到的情況，是因為異步任務(wù)在未執(zhí)行完畢的情況下，主線程已經(jīng)返回，拷貝共享的Request對象數(shù)據(jù)被清空

ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
//設(shè)置子線程共享
RequestContextHolder.setRequestAttributes(servletRequestAttributes, true);
HttpServletRequest request = servletRequestAttributes.getRequest();

解決方案

前置條件

啟動類添加@EnableAsync注解
標(biāo)記@Async的異步方法不能和調(diào)用者在同一個class中

pom配置

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

requrest共享

通過TransmittableThreadLocal對象進行線程對象共享

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：系統(tǒng)中所有Request獲取需要統(tǒng)一從CommonUtil指定來源，例如token鑒權(quán)等

自定義request過濾器

通過自定義過濾器對Request的內(nèi)容進行備份保存，主線程結(jié)束時Request清除結(jié)束不會影響到子線程的相應(yīng)參數(shù)的獲取，也適用于增加攔截器/過濾器后body參數(shù)無法重復(fù)獲取的問題。需要注意的是對header參數(shù)處理時key要忽略大小寫

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);
        }
        //獲取請求中的流如何，將取出來的字符串，再次轉(zhuǎn)換成流，然后把它放入到新request對象中。
        // 在chain.doFiler方法中傳遞新的request對象
        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);
    }
}

自定義任務(wù)執(zhí)行器

用于攔截異步任務(wù)執(zhí)行，在任務(wù)執(zhí)前統(tǒng)一進行Request共享操作，且可以定義多個，不影響原有的異步任務(wù)代碼

public class CustomTaskDecorator implements TaskDecorator {
    @Override
    public Runnable decorate(Runnable runnable) {
        ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = requestAttributes.getRequest();
        System.out.println("異步任務(wù)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 屬性的配置
        executor.setTaskDecorator(new CustomTaskDecorator());
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        executor.initialize();
        return executor;
    }
}

調(diào)用示例

給@Anysc注解指定進行共享攔截的任務(wù)執(zhí)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("開始執(zhí)行executeAsync");
        Thread.sleep(3000);
        System.out.println("結(jié)束執(zhí)行executeAsync");
    }
}

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