蚌埠网站建设费用,网易企业邮箱收费多少,模板建站总公司,广东住房和城乡建设厅官网一、背景
接到一个需求#xff0c;实现方案时需要提供一个HTTP接口#xff0c;接口需要hold住5-8秒#xff0c;轮询查询数据库#xff0c;一旦数据库中值有变化#xff0c;取出变化的值进行处理#xff0c;处理完成后返回响应。这不就是长轮询吗#xff0c;如何优雅的实…一、背景
接到一个需求实现方案时需要提供一个HTTP接口接口需要hold住5-8秒轮询查询数据库一旦数据库中值有变化取出变化的值进行处理处理完成后返回响应。这不就是长轮询吗如何优雅的实现呢
二、方案设计
在 Spring 中AsyncContext 是用于支持异步处理的一个重要的特性。它允许我们在 servlet 请求处理过程中将长时间运行的操作放在一个单独的线程中执行而不会阻塞其他请求的处理。
AsyncContext 在以下两种情况下特别有用 长时间运行的操作当我们需要执行一些耗时的操作例如网络请求、数据库查询或其他 I/O 操作时通过将这些操作放在一个新的线程中可以避免阻塞 servlet 容器中的线程提高应用的并发性能。 推送异步响应有时候我们可能需要推送异步产生的响应而不是等到所有操作都完成后再下发响应。通过 AsyncContext我们可以在任何时间点上触发异步响应将结果返回给客户端。
使用 AsyncContext 的步骤如下
在 servlet 中启用异步模式在 servlet 中通过调用 startAsync() 方法可以获取到当前请求的 AsyncContext 对象从而启用异步处理模式。
HttpServletRequest request ...;
AsyncContext asyncContext request.startAsync();指定异步任务通过调用 AsyncContext 对象的 start() 方法在新的线程中执行需要异步处理的任务。
asyncContext.start(() - {// 异步任务逻辑
});提交响应在异步任务完成后可以调用 AsyncContext 对象的 complete() 方法以表示异步操作完成。
asyncContext.complete();需要注意的是我们在使用 AsyncContext 时需要特别注意线程安全。由于异步任务在单独的线程中执行所以可能存在并发问题。因此在编写异步任务逻辑时需要注意线程安全性使用合适的同步措施。
另外AsyncContext 也支持超时设置、错误处理、事件监听等功能这些可以通过相应的方法和回调进行配置。可以根据具体的需求使用这些功能来优化异步处理的逻辑。
总结来说Spring 的 AsyncContext 提供了方便的异步处理机制可以提高应用的并发性能并支持推送异步响应使得应用更具有响应性和可伸缩性。
三、代码1
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.concurrent.*;RestController
RequestMapping(/api/byai/transform)
Slf4j
public class AsyncTestController {Resourceprivate RedisTemplateString, String redisTemplate;private final ExecutorService timeoutChecker new ThreadPoolExecutor(1,1,1000,TimeUnit.SECONDS,new ArrayBlockingQueue(1000));private static final ThreadFactory threadFactory new ThreadFactoryBuilder().setNameFormat(longPolling-timeout-checker-%d).build();// private static boolean result false;PostMapping(/async)public void async(HttpServletRequest request, HttpServletResponse response) {// 创建AsyncContextAsyncContext asyncContext request.startAsync(request, response);// 设置处理超时时间8sasyncContext.setTimeout(8000L);// asyncContext监听JdAsyncTestListener asyncListener new JdAsyncTestListener(redisTemplate,asyncContext);asyncContext.addListener(asyncListener);// 定时处理业务处理成功后asyncContext.complete();完成异步请求asyncContext.start(asyncListener);}// 模拟业务处理完成PostMapping(/set)public ResultModel notify(String key, String value) {redisTemplate.opsForValue().set(key, value);return ResultModel.success();}PostMapping(/get)public ResultModel get(String key) {String s redisTemplate.opsForValue().get(key);return ResultModel.success(s);}PostMapping(/del)public ResultModel del(String key) {redisTemplate.delete(key);return ResultModel.success();}
}
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.concurrent.*;RestController
RequestMapping(/api/test)
Slf4j
public class AsyncTestController {Resourceprivate RedisTemplateString, String redisTemplate;private final ExecutorService timeoutChecker new ThreadPoolExecutor(1,1,1000,TimeUnit.SECONDS,new ArrayBlockingQueue(1000));private static final ThreadFactory threadFactory new ThreadFactoryBuilder().setNameFormat(longPolling-timeout-checker-%d).build();// private static boolean result false;PostMapping(/async)public void async(HttpServletRequest request, HttpServletResponse response) {// 创建AsyncContextAsyncContext asyncContext request.startAsync(request, response);// 设置处理超时时间8sasyncContext.setTimeout(8000L);// asyncContext监听JdAsyncTestListener asyncListener new JdAsyncTestListener(redisTemplate,asyncContext);asyncContext.addListener(asyncListener);// 定时处理业务处理成功后asyncContext.complete();完成异步请求asyncContext.start(asyncListener);}// 模拟业务处理完成PostMapping(/set)public ResultModel notify(String key, String value) {redisTemplate.opsForValue().set(key, value);return ResultModel.success();}PostMapping(/get)public ResultModel get(String key) {String s redisTemplate.opsForValue().get(key);return ResultModel.success(s);}PostMapping(/del)public ResultModel del(String key) {redisTemplate.delete(key);return ResultModel.success();}
}
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.RedisTemplate;import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import java.io.IOException;Slf4j
public class JdAsyncTestListener implements AsyncListener,Runnable {boolean isComplete;private RedisTemplateString, String redisTemplate;private AsyncContext asyncContext;public JdAsyncTestListener(RedisTemplateString, String redisTemplate, AsyncContext asyncContext) {this.redisTemplate redisTemplate;this.asyncContext asyncContext;}Overridepublic void run() {try {while(true){if(isComplete){log.info(已经退出);break;}boolean b redisTemplate.opsForValue().get(1) ! null;log.info(获取标志位:b);Thread.sleep(300);if (b) {asyncContext.getResponse().getWriter().print(1);asyncContext.complete();}}} catch (IOException e) {e.printStackTrace();} catch (InterruptedException e) {throw new RuntimeException(e);}}Overridepublic void onComplete(AsyncEvent asyncEvent) throws IOException {log.info(结束了);isComplete true;}Overridepublic void onTimeout(AsyncEvent asyncEvent) throws IOException {log.info(超时了);isComplete true;}Overridepublic void onError(AsyncEvent asyncEvent) throws IOException {}Overridepublic void onStartAsync(AsyncEvent asyncEvent) throws IOException {}
}
四、代码二
import com.alibaba.fastjson.JSON;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.apache.dubbo.config.annotation.Reference;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.concurrent.*;Validated
RestController
RequestMapping(/api/test)
Slf4j
public class TestController {Resourceprivate RedisTemplateString, String redisTemplate;private final ScheduledExecutorService timeoutChecker new ScheduledThreadPoolExecutor(10, threadFactory);private static final ThreadFactory threadFactory new ThreadFactoryBuilder().setNameFormat(longPolling-timeout-checker-%d).build();private static boolean result false;private final boolean isTimeout false;/*** 消息** return*/PostMapping(/test)public void callback(RequestBody TestLongPollRequest testLongPollRequest, HttpServletRequest request, HttpServletResponse response) {// 创建AsyncContextAsyncContext asyncContext request.startAsync(request, response);String jdCustomerId jdLongPollRequest.getJdCustomerId();// 设置处理超时时间8sasyncContext.setTimeout(8000L);// asyncContext监听asyncContext.addListener(new AsyncListener() {Overridepublic void onComplete(AsyncEvent asyncEvent) throws IOException {log.info(onComplete{}, asyncEvent);}Overridepublic void onTimeout(AsyncEvent asyncEvent) throws IOException {log.info(onTimeout{}, asyncEvent);ConcurrentHashMapString, String map new ConcurrentHashMap();map.put(code, 500); asyncContext.getResponse().getWriter().print(JSON.toJSONString(map));asyncContext.complete();}Overridepublic void onError(AsyncEvent asyncEvent) throws IOException {log.info(onError{}, asyncEvent);}Overridepublic void onStartAsync(AsyncEvent asyncEvent) throws IOException {log.info(onStartAsync{}, asyncEvent);}});// 定时处理业务处理成功后asyncContext.complete();完成异步请求timeoutChecker.scheduleAtFixedRate(() - {try {String redisKey getcustomerProcessRes(customerId);String redisValue redisTemplate.opsForValue().get(redisKey);result StringUtils.isNotBlank(redisValue);if (result) {//todo 长轮询查询数据库。通过customerId查询send(customerId, redisValue);ConcurrentHashMapString, String map new ConcurrentHashMap();map.put(code, 200);map.put(msg, redisValue);asyncContext.getResponse().getWriter().print(JSON.toJSONString(map));asyncContext.complete();}} catch (IOException e) {e.printStackTrace();}}, 0, 100L, TimeUnit.MILLISECONDS);}/*** 发送消息*/private void send(String customerId, String content) {}}
