基于springboot 长轮询的实现操作

@SpringBootApplication
@EnableAsync
public class DemoApplication {
 public static void main(String[] args) {
 SpringApplication.run(DemoApplication.class, args);
 }
}

@RequestMapping("/async")
@RestController
public class AsyncRequestDemo {
 @Autowired
 private AsyncRequestService asyncRequestService;
 @GetMapping("/value")
 public String getValue() {
 String msg = null;
 Future<String> result = null;
 try{
  result = asyncRequestService.getValue();
  msg = result.get(10, TimeUnit.SECONDS);
 }catch (Exception e){
  e.printStackTrace();
 }finally {
  if (result != null){
  result.cancel(true);
  }
 }
 return msg;
 }
 @PostMapping("/value")
 public void postValue(String msg) {
 asyncRequestService.postValue(msg);
 }
}

@Service
public class AsyncRequestService {
 private String msg = null;
 @Async
 public Future<String> getValue() throws InterruptedException {
 while (true){
  synchronized (this){
  if (msg != null){
   String resultMsg = msg;
   msg = null;
   return new AsyncResult(resultMsg);
  }
  }
  Thread.sleep(100);
 }
 }
 public synchronized void postValue(String msg) {
 this.msg = msg;
 }
}

@SpringBootApplication
public class DemoApplication implements WebMvcConfigurer { 
 public static void main(String[] args) {
 SpringApplication.run(DemoApplication.class, args);
 } 
 
 @Bean
 public ThreadPoolTaskExecutor mvcTaskExecutor() {
 ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
 executor.setCorePoolSize(10);
 executor.setQueueCapacity(100);
 executor.setMaxPoolSize(25);
 return executor;
 
 }
 
 //配置异步支持，设置了一个用来异步执行业务逻辑的工作线程池，设置了默认的超时时间是60秒
 @Override
 public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
 configurer.setTaskExecutor(mvcTaskExecutor());
 configurer.setDefaultTimeout(60000L);
 }
}

import com.google.common.collect.HashMultimap;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.async.DeferredResult; 
import java.util.Collection;
 
@RestController
public class ApolloController {
 private final Logger logger = LoggerFactory.getLogger(this.getClass());
 
 //guava中的Multimap，多值map,对map的增强，一个key可以保持多个value
 private Multimap<String, DeferredResult<String>> watchRequests = Multimaps.synchronizedSetMultimap(HashMultimap.create());
 
 
 //模拟长轮询
 @RequestMapping(value = "/watch/{namespace}", method = RequestMethod.GET, produces = "text/html")
 public DeferredResult<String> watch(@PathVariable("namespace") String namespace) {
 logger.info("Request received");
 DeferredResult<String> deferredResult = new DeferredResult<>();
 //当deferredResult完成时（不论是超时还是异常还是正常完成），移除watchRequests中相应的watch key
 deferredResult.onCompletion(new Runnable() {
  @Override
  public void run() {
  System.out.println("remove key:" + namespace);
  watchRequests.remove(namespace, deferredResult);
  }
 });
 watchRequests.put(namespace, deferredResult);
 logger.info("Servlet thread released");
 return deferredResult;
 
 
 }
 
 //模拟发布namespace配置
 @RequestMapping(value = "/publish/{namespace}", method = RequestMethod.GET, produces = "text/html")
 public Object publishConfig(@PathVariable("namespace") String namespace) {
 if (watchRequests.containsKey(namespace)) {
  Collection<DeferredResult<String>> deferredResults = watchRequests.get(namespace);
  Long time = System.currentTimeMillis();
  //通知所有watch这个namespace变更的长轮训配置变更结果
  for (DeferredResult<String> deferredResult : deferredResults) {
  deferredResult.setResult(namespace + " changed:" + time);
  }
 }
 return "success";
 
 }
}

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.context.request.async.AsyncRequestTimeoutException;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@ControllerAdvice
class GlobalControllerExceptionHandler {
 
 protected static final Logger logger = LoggerFactory.getLogger(GlobalControllerExceptionHandler.class);
 
 @ResponseStatus(HttpStatus.NOT_MODIFIED)//返回304状态码
 @ResponseBody
 @ExceptionHandler(AsyncRequestTimeoutException.class) //捕获特定异常
 public void handleAsyncRequestTimeoutException(AsyncRequestTimeoutException e, HttpServletRequest request) {
 System.out.println("handleAsyncRequestTimeoutException");
 }
}

mynamespace changed:1538880050147