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[spring6: Mvc-异步请求]-源码分析

ds 2025/7/28 16:45:57

源码

Callable

Callable 是一个带返回值且可抛异常的任务接口。

@FunctionalInterface
public interface Callable<V> {V call() throws Exception;}

WebAsyncTask

WebAsyncTask 是 Callable 的增强版本，支持自定义超时时间和执行线程池，实现更灵活的异步请求处理。

public class WebAsyncTask<V> implements BeanFactoryAware {private final Callable<V> callable;@Nullableprivate final Long timeout;@Nullableprivate final AsyncTaskExecutor executor;@Nullableprivate final String executorName;@Nullableprivate BeanFactory beanFactory;@Nullableprivate Callable<V> timeoutCallback;@Nullableprivate Callable<V> errorCallback;@Nullableprivate Runnable completionCallback;public WebAsyncTask(Callable<V> callable) {Assert.notNull(callable, "Callable must not be null");this.callable = callable;this.timeout = null;this.executor = null;this.executorName = null;}public WebAsyncTask(long timeout, Callable<V> callable) {Assert.notNull(callable, "Callable must not be null");this.callable = callable;this.timeout = timeout;this.executor = null;this.executorName = null;}public WebAsyncTask(@Nullable Long timeout, String executorName, Callable<V> callable) {Assert.notNull(callable, "Callable must not be null");Assert.notNull(executorName, "Executor name must not be null");this.callable = callable;this.timeout = timeout;this.executor = null;this.executorName = executorName;}public WebAsyncTask(@Nullable Long timeout, AsyncTaskExecutor executor, Callable<V> callable) {Assert.notNull(callable, "Callable must not be null");Assert.notNull(executor, "Executor must not be null");this.callable = callable;this.timeout = timeout;this.executor = executor;this.executorName = null;}public Callable<?> getCallable() {return this.callable;}@Nullablepublic Long getTimeout() {return this.timeout;}@Overridepublic void setBeanFactory(BeanFactory beanFactory) {this.beanFactory = beanFactory;}@Nullablepublic AsyncTaskExecutor getExecutor() {if (this.executor != null) {return this.executor;}else if (this.executorName != null) {Assert.state(this.beanFactory != null, "BeanFactory is required to look up an executor bean by name");return this.beanFactory.getBean(this.executorName, AsyncTaskExecutor.class);}else {return null;}}public void onTimeout(Callable<V> callback) {this.timeoutCallback = callback;}public void onError(Callable<V> callback) {this.errorCallback = callback;}public void onCompletion(Runnable callback) {this.completionCallback = callback;}CallableProcessingInterceptor getInterceptor() {return new CallableProcessingInterceptor() {@Overridepublic <T> Object handleTimeout(NativeWebRequest request, Callable<T> task) throws Exception {return (timeoutCallback != null ? timeoutCallback.call() : CallableProcessingInterceptor.RESULT_NONE);}@Overridepublic <T> Object handleError(NativeWebRequest request, Callable<T> task, Throwable t) throws Exception {return (errorCallback != null ? errorCallback.call() : CallableProcessingInterceptor.RESULT_NONE);}@Overridepublic <T> void afterCompletion(NativeWebRequest request, Callable<T> task) throws Exception {if (completionCallback != null) {completionCallback.run();}}};}}

DeferredResult

DeferredResult 允许异步请求处理中，应用线程自主设置结果并注册超时、错误和完成回调。

public class DeferredResult<T> {private static final Object RESULT_NONE = new Object();private static final Log logger = LogFactory.getLog(DeferredResult.class);@Nullableprivate final Long timeoutValue;private final Supplier<?> timeoutResult;@Nullableprivate Runnable timeoutCallback;@Nullableprivate Consumer<Throwable> errorCallback;@Nullableprivate Runnable completionCallback;@Nullableprivate DeferredResultHandler resultHandler;@Nullableprivate volatile Object result = RESULT_NONE;private volatile boolean expired;public DeferredResult() {this(null);}public DeferredResult(@Nullable Long timeoutValue) {this(timeoutValue, () -> RESULT_NONE);}public DeferredResult(@Nullable Long timeoutValue, Object timeoutResult) {this(timeoutValue, () -> timeoutResult);}public DeferredResult(@Nullable Long timeoutValue, Supplier<?> timeoutResult) {this.timeoutValue = timeoutValue;this.timeoutResult = timeoutResult;}public final boolean isSetOrExpired() {return (this.result != RESULT_NONE || this.expired);}public boolean hasResult() {return (this.result != RESULT_NONE);}@Nullablepublic Object getResult() {Object resultToCheck = this.result;return (resultToCheck != RESULT_NONE ? resultToCheck : null);}@Nullablefinal Long getTimeoutValue() {return this.timeoutValue;}public void onTimeout(Runnable callback) {this.timeoutCallback = callback;}public void onError(Consumer<Throwable> callback) {this.errorCallback = callback;}public void onCompletion(Runnable callback) {this.completionCallback = callback;}public final void setResultHandler(DeferredResultHandler resultHandler) {Assert.notNull(resultHandler, "DeferredResultHandler is required");if (this.expired) {return;}Object resultToHandle;synchronized (this) {if (this.expired) {return;}resultToHandle = this.result;if (resultToHandle == RESULT_NONE) {this.resultHandler = resultHandler;return;}}try {resultHandler.handleResult(resultToHandle);}catch (Throwable ex) {logger.debug("Failed to process async result", ex);}}public boolean setResult(@Nullable T result) {return setResultInternal(result);}private boolean setResultInternal(@Nullable Object result) {if (isSetOrExpired()) {return false;}DeferredResultHandler resultHandlerToUse;synchronized (this) {if (isSetOrExpired()) {return false;}this.result = result;resultHandlerToUse = this.resultHandler;if (resultHandlerToUse == null) {return true;}this.resultHandler = null;}resultHandlerToUse.handleResult(result);return true;}public boolean setErrorResult(Object result) {return setResultInternal(result);}final DeferredResultProcessingInterceptor getLifecycleInterceptor() {return new LifecycleInterceptor();}@FunctionalInterfacepublic interface DeferredResultHandler {void handleResult(@Nullable Object result);}private class LifecycleInterceptor implements DeferredResultProcessingInterceptor {@Overridepublic <S> boolean handleTimeout(NativeWebRequest request, DeferredResult<S> result) {boolean continueProcessing = true;try {if (timeoutCallback != null) {timeoutCallback.run();}}finally {Object value = timeoutResult.get();if (value != RESULT_NONE) {continueProcessing = false;try {setResultInternal(value);}catch (Throwable ex) {logger.debug("Failed to handle timeout result", ex);}}}return continueProcessing;}@Overridepublic <S> boolean handleError(NativeWebRequest request, DeferredResult<S> result, Throwable t) {try {if (errorCallback != null) {errorCallback.accept(t);}}finally {try {setResultInternal(t);}catch (Throwable ex) {logger.debug("Failed to handle error result", ex);}}return false;}@Overridepublic <S> void afterCompletion(NativeWebRequest request, DeferredResult<S> result) {expired = true;if (completionCallback != null) {completionCallback.run();}}}
}

AsyncContext

AsyncContext 是 Servlet 3.0 提供的异步处理上下文，允许请求线程释放并异步执行任务，最终通过手动完成响应或分发继续处理。

public interface AsyncContext {String ASYNC_REQUEST_URI = "jakarta.servlet.async.request_uri";String ASYNC_CONTEXT_PATH = "jakarta.servlet.async.context_path";String ASYNC_MAPPING = "jakarta.servlet.async.mapping";String ASYNC_PATH_INFO = "jakarta.servlet.async.path_info";String ASYNC_SERVLET_PATH = "jakarta.servlet.async.servlet_path";String ASYNC_QUERY_STRING = "jakarta.servlet.async.query_string";ServletRequest getRequest();ServletResponse getResponse();boolean hasOriginalRequestAndResponse();void dispatch();void dispatch(String path);void dispatch(ServletContext context, String path);void complete();void start(Runnable run);void addListener(AsyncListener listener);void addListener(AsyncListener listener, ServletRequest request, ServletResponse response);<T extends AsyncListener> T createListener(Class<T> clazz) throws ServletException;void setTimeout(long timeout);long getTimeout();
}

原理

CallableMethodReturnValueHandler

CallableMethodReturnValueHandler 负责处理控制器方法返回的 Callable 类型，借助 WebAsyncManager 启动异步执行并挂起请求，由 Spring MVC 异步处理机制在任务完成后恢复响应。

// RequestMappingHandlerAdapter.handleInternal ->  
// 	 RequestMappingHandlerAdapter.invokeHandlerMethod ->
//	    ServletInvocableHandlerMethod.invokeAndHandle -> 
// 		  HandlerMethodReturnValueHandlerComposite.handleReturnValue ->
//			HandlerMethodReturnValueHandlerComposite.selectHandler ->
public class CallableMethodReturnValueHandler implements HandlerMethodReturnValueHandler {@Overridepublic boolean supportsReturnType(MethodParameter returnType) {return Callable.class.isAssignableFrom(returnType.getParameterType());}@Overridepublic void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {if (returnValue == null) {mavContainer.setRequestHandled(true);return;}Callable<?> callable = (Callable<?>) returnValue;WebAsyncUtils.getAsyncManager(webRequest).startCallableProcessing(callable, mavContainer);}}

AsyncTaskMethodReturnValueHandler

AsyncTaskMethodReturnValueHandler 用于处理返回值为 WebAsyncTask 的方法，借助 WebAsyncManager 启动异步调用流程，并可注入 BeanFactory 支持自定义线程池与回调配置。

public class AsyncTaskMethodReturnValueHandler implements HandlerMethodReturnValueHandler {@Nullableprivate final BeanFactory beanFactory;public AsyncTaskMethodReturnValueHandler(@Nullable BeanFactory beanFactory) {this.beanFactory = beanFactory;}@Overridepublic boolean supportsReturnType(MethodParameter returnType) {return WebAsyncTask.class.isAssignableFrom(returnType.getParameterType());}@Overridepublic void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {if (returnValue == null) {mavContainer.setRequestHandled(true);return;}WebAsyncTask<?> webAsyncTask = (WebAsyncTask<?>) returnValue;if (this.beanFactory != null) {webAsyncTask.setBeanFactory(this.beanFactory);}WebAsyncUtils.getAsyncManager(webRequest).startCallableProcessing(webAsyncTask, mavContainer);}}

DeferredResultMethodReturnValueHandler

DeferredResultMethodReturnValueHandler 处理控制器返回的 DeferredResult、ListenableFuture 或 CompletionStage，通过 WebAsyncManager 启动异步处理，挂起请求并在结果就绪时恢复响应流程。

// RequestMappingHandlerAdapter.handleInternal ->  
// 	 RequestMappingHandlerAdapter.invokeHandlerMethod ->
//	    ServletInvocableHandlerMethod.invokeAndHandle -> 
// 		  HandlerMethodReturnValueHandlerComposite.handleReturnValue ->
//			HandlerMethodReturnValueHandlerComposite.selectHandler ->
public class DeferredResultMethodReturnValueHandler implements HandlerMethodReturnValueHandler {@SuppressWarnings({"deprecation", "removal"})@Overridepublic boolean supportsReturnType(MethodParameter returnType) {Class<?> type = returnType.getParameterType();return (DeferredResult.class.isAssignableFrom(type) ||org.springframework.util.concurrent.ListenableFuture.class.isAssignableFrom(type) ||CompletionStage.class.isAssignableFrom(type));}@SuppressWarnings({"deprecation", "removal"})@Overridepublic void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {if (returnValue == null) {mavContainer.setRequestHandled(true);return;}DeferredResult<?> result;if (returnValue instanceof DeferredResult<?> deferredResult) {result = deferredResult;}else if (returnValue instanceof org.springframework.util.concurrent.ListenableFuture<?> listenableFuture) {result = adaptListenableFuture(listenableFuture);}else if (returnValue instanceof CompletionStage<?> completionStage) {result = adaptCompletionStage(completionStage);}else {// Should not happen...throw new IllegalStateException("Unexpected return value type: " + returnValue);}WebAsyncUtils.getAsyncManager(webRequest).startDeferredResultProcessing(result, mavContainer);}@SuppressWarnings({"deprecation", "removal"})private DeferredResult<Object> adaptListenableFuture(org.springframework.util.concurrent.ListenableFuture<?> future) {DeferredResult<Object> result = new DeferredResult<>();future.addCallback(new org.springframework.util.concurrent.ListenableFutureCallback<Object>() {@Overridepublic void onSuccess(@Nullable Object value) {result.setResult(value);}@Overridepublic void onFailure(Throwable ex) {result.setErrorResult(ex);}});return result;}private DeferredResult<Object> adaptCompletionStage(CompletionStage<?> future) {DeferredResult<Object> result = new DeferredResult<>();future.whenComplete((value, ex) -> {if (ex != null) {if (ex instanceof CompletionException && ex.getCause() != null) {ex = ex.getCause();}result.setErrorResult(ex);}else {result.setResult(value);}});return result;}}

WebAsyncManager

WebAsyncManager 是 Spring MVC 异步请求的核心管理器，负责协调异步任务执行、超时和错误处理，并在结果就绪后触发异步分派恢复请求流程。

public final class WebAsyncManager {private static final Object RESULT_NONE = new Object();private static final AsyncTaskExecutor DEFAULT_TASK_EXECUTOR = new SimpleAsyncTaskExecutor(WebAsyncManager.class.getSimpleName());private static final Log logger = LogFactory.getLog(WebAsyncManager.class);private static final CallableProcessingInterceptor timeoutCallableInterceptor = new TimeoutCallableProcessingInterceptor();private static final DeferredResultProcessingInterceptor timeoutDeferredResultInterceptor = new TimeoutDeferredResultProcessingInterceptor();@Nullableprivate AsyncWebRequest asyncWebRequest;private AsyncTaskExecutor taskExecutor = DEFAULT_TASK_EXECUTOR;private boolean isMultipartRequestParsed;@Nullableprivate volatile Object concurrentResult = RESULT_NONE;@Nullableprivate volatile Object[] concurrentResultContext;private final AtomicReference<State> state = new AtomicReference<>(State.NOT_STARTED);private final Map<Object, CallableProcessingInterceptor> callableInterceptors = new LinkedHashMap<>();private final Map<Object, DeferredResultProcessingInterceptor> deferredResultInterceptors = new LinkedHashMap<>();WebAsyncManager() {}@SuppressWarnings({"rawtypes", "unchecked"})public void startCallableProcessing(Callable<?> callable, Object... processingContext) throws Exception {Assert.notNull(callable, "Callable must not be null");startCallableProcessing(new WebAsyncTask(callable), processingContext);}@SuppressWarnings("NullAway")public void startCallableProcessing(final WebAsyncTask<?> webAsyncTask, Object... processingContext) throws Exception {Assert.notNull(webAsyncTask, "WebAsyncTask must not be null");Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");if (!this.state.compareAndSet(State.NOT_STARTED, State.ASYNC_PROCESSING)) {throw new IllegalStateException("Unexpected call to startCallableProcessing: [" + this.state.get() + "]");}Long timeout = webAsyncTask.getTimeout();if (timeout != null) {this.asyncWebRequest.setTimeout(timeout);}AsyncTaskExecutor executor = webAsyncTask.getExecutor();if (executor != null) {this.taskExecutor = executor;}List<CallableProcessingInterceptor> interceptors = new ArrayList<>();interceptors.add(webAsyncTask.getInterceptor());interceptors.addAll(this.callableInterceptors.values());interceptors.add(timeoutCallableInterceptor);final Callable<?> callable = webAsyncTask.getCallable();final CallableInterceptorChain interceptorChain = new CallableInterceptorChain(interceptors);this.asyncWebRequest.addTimeoutHandler(() -> {if (logger.isDebugEnabled()) {logger.debug("Servlet container timeout notification for " + formatUri(this.asyncWebRequest));}Object result = interceptorChain.triggerAfterTimeout(this.asyncWebRequest, callable);if (result != CallableProcessingInterceptor.RESULT_NONE) {setConcurrentResultAndDispatch(result);}});this.asyncWebRequest.addErrorHandler(ex -> {if (logger.isDebugEnabled()) {logger.debug("Servlet container error notification for " + formatUri(this.asyncWebRequest) + ": " + ex);}if (DisconnectedClientHelper.isClientDisconnectedException(ex)) {ex = new AsyncRequestNotUsableException("Servlet container error notification for disconnected client", ex);}Object result = interceptorChain.triggerAfterError(this.asyncWebRequest, callable, ex);result = (result != CallableProcessingInterceptor.RESULT_NONE ? result : ex);setConcurrentResultAndDispatch(result);});this.asyncWebRequest.addCompletionHandler(() -> interceptorChain.triggerAfterCompletion(this.asyncWebRequest, callable));interceptorChain.applyBeforeConcurrentHandling(this.asyncWebRequest, callable);startAsyncProcessing(processingContext);try {Future<?> future = this.taskExecutor.submit(() -> {Object result = null;try {interceptorChain.applyPreProcess(this.asyncWebRequest, callable);result = callable.call();}catch (Throwable ex) {result = ex;}finally {result = interceptorChain.applyPostProcess(this.asyncWebRequest, callable, result);}setConcurrentResultAndDispatch(result);});interceptorChain.setTaskFuture(future);}catch (Throwable ex) {Object result = interceptorChain.applyPostProcess(this.asyncWebRequest, callable, ex);setConcurrentResultAndDispatch(result);}}@SuppressWarnings("NullAway")public void startDeferredResultProcessing(final DeferredResult<?> deferredResult, Object... processingContext) throws Exception {Assert.notNull(deferredResult, "DeferredResult must not be null");Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");if (!this.state.compareAndSet(State.NOT_STARTED, State.ASYNC_PROCESSING)) {throw new IllegalStateException("Unexpected call to startDeferredResultProcessing: [" + this.state.get() + "]");}Long timeout = deferredResult.getTimeoutValue();if (timeout != null) {this.asyncWebRequest.setTimeout(timeout);}List<DeferredResultProcessingInterceptor> interceptors = new ArrayList<>();interceptors.add(deferredResult.getLifecycleInterceptor());interceptors.addAll(this.deferredResultInterceptors.values());interceptors.add(timeoutDeferredResultInterceptor);final DeferredResultInterceptorChain interceptorChain = new DeferredResultInterceptorChain(interceptors);this.asyncWebRequest.addTimeoutHandler(() -> {if (logger.isDebugEnabled()) {logger.debug("Servlet container timeout notification for " + formatUri(this.asyncWebRequest));}try {interceptorChain.triggerAfterTimeout(this.asyncWebRequest, deferredResult);synchronized (WebAsyncManager.this) {// If application thread set the DeferredResult first in a race,// we must still not return until setConcurrentResultAndDispatch is donereturn;}}catch (Throwable ex) {setConcurrentResultAndDispatch(ex);}});this.asyncWebRequest.addErrorHandler(ex -> {if (logger.isDebugEnabled()) {logger.debug("Servlet container error notification for " + formatUri(this.asyncWebRequest));}if (DisconnectedClientHelper.isClientDisconnectedException(ex)) {ex = new AsyncRequestNotUsableException("Servlet container error notification for disconnected client", ex);}try {interceptorChain.triggerAfterError(this.asyncWebRequest, deferredResult, ex);synchronized (WebAsyncManager.this) {// If application thread set the DeferredResult first in a race,// we must still not return until setConcurrentResultAndDispatch is donereturn;}}catch (Throwable interceptorEx) {setConcurrentResultAndDispatch(interceptorEx);}});this.asyncWebRequest.addCompletionHandler(() ->interceptorChain.triggerAfterCompletion(this.asyncWebRequest, deferredResult));interceptorChain.applyBeforeConcurrentHandling(this.asyncWebRequest, deferredResult);startAsyncProcessing(processingContext);try {interceptorChain.applyPreProcess(this.asyncWebRequest, deferredResult);deferredResult.setResultHandler(result -> {result = interceptorChain.applyPostProcess(this.asyncWebRequest, deferredResult, result);setConcurrentResultAndDispatch(result);});}catch (Throwable ex) {setConcurrentResultAndDispatch(ex);}}private void startAsyncProcessing(Object[] processingContext) {synchronized (WebAsyncManager.this) {this.concurrentResult = RESULT_NONE;this.concurrentResultContext = processingContext;}Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");if (logger.isDebugEnabled()) {logger.debug("Started async request for " + formatUri(this.asyncWebRequest));}this.asyncWebRequest.startAsync();}private void setConcurrentResultAndDispatch(@Nullable Object result) {Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");synchronized (WebAsyncManager.this) {if (!this.state.compareAndSet(State.ASYNC_PROCESSING, State.RESULT_SET)) {if (logger.isDebugEnabled()) {logger.debug("Async result already set: [" + this.state.get() + "], " +"ignored result for " + formatUri(this.asyncWebRequest));}return;}this.concurrentResult = result;if (logger.isDebugEnabled()) {logger.debug("Async result set for " + formatUri(this.asyncWebRequest));}if (this.asyncWebRequest.isAsyncComplete()) {if (logger.isDebugEnabled()) {logger.debug("Async request already completed for " + formatUri(this.asyncWebRequest));}return;}if (logger.isDebugEnabled()) {logger.debug("Performing async dispatch for " + formatUri(this.asyncWebRequest));}this.asyncWebRequest.dispatch();}}
}

StandardServletAsyncWebRequest

StandardServletAsyncWebRequest 是 Spring 框架中封装 Servlet 3.0 异步处理机制的类，用于管理异步请求的启动、超时和完成通知。

public class StandardServletAsyncWebRequest extends ServletWebRequest implements AsyncWebRequest, AsyncListener {private final List<Runnable> timeoutHandlers = new ArrayList<>();private final List<Consumer<Throwable>> exceptionHandlers = new ArrayList<>();private final List<Runnable> completionHandlers = new ArrayList<>();@Nullableprivate Long timeout;@Nullableprivate AsyncContext asyncContext;private State state;private final ReentrantLock stateLock = new ReentrantLock();public StandardServletAsyncWebRequest(HttpServletRequest request, HttpServletResponse response) {this(request, response, null);}@SuppressWarnings("NullAway")StandardServletAsyncWebRequest(HttpServletRequest request, HttpServletResponse response, @Nullable StandardServletAsyncWebRequest previousRequest) {super(request, new LifecycleHttpServletResponse(response));this.state = (previousRequest != null ? previousRequest.state : State.NEW);//noinspection DataFlowIssue((LifecycleHttpServletResponse) getResponse()).setAsyncWebRequest(this);}@Overridepublic void startAsync() {Assert.state(getRequest().isAsyncSupported(),"Async support must be enabled on a servlet and for all filters involved " +"in async request processing. This is done in Java code using the Servlet API " +"or by adding \"<async-supported>true</async-supported>\" to servlet and " +"filter declarations in web.xml.");if (isAsyncStarted()) {return;}if (this.state == State.NEW) {this.state = State.ASYNC;}else {Assert.state(this.state == State.ASYNC, "Cannot start async: [" + this.state + "]");}this.asyncContext = getRequest().startAsync(getRequest(), getResponse());this.asyncContext.addListener(this);if (this.timeout != null) {this.asyncContext.setTimeout(this.timeout);}}@Overridepublic void dispatch() {Assert.state(this.asyncContext != null, "AsyncContext not yet initialized");if (!this.isAsyncComplete()) {this.asyncContext.dispatch();}}// ...}

实战

@RestController
@SpringBootApplication
public class Application {@Autowired@Qualifier(TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME)private AsyncTaskExecutor applicationTaskExecutor;@GetMapping("/deferredResult")public DeferredResult<String> deferredResult() {DeferredResult<String> deferredResult = new DeferredResult<>(3000L, "timeout");applicationTaskExecutor.execute(() -> {try {Thread.sleep(5000); deferredResult.setResult("deferredResult");} catch (InterruptedException e) {e.printStackTrace();}});return deferredResult;}@GetMapping("/webAsyncTask")public WebAsyncTask<String> webAsyncTask() {return new WebAsyncTask<String>(3000L,() -> { Thread.sleep(1000);return "webAsyncTask";});}@GetMapping("/callable")public Callable<String> callable() {return () -> "callable";}@GetMapping("/asyncContext")public void asyncContext(HttpServletRequest request, HttpServletResponse response) {AsyncContext asyncContext = request.startAsync();asyncContext.start(() -> {try {Thread.sleep(2000);response.getWriter().write("asyncContext");} catch (Exception e) {e.printStackTrace();} finally {asyncContext.complete();}});}public static void main(String[] args) {SpringApplication.run(Application.class, args);}}
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