本文主要是介绍Java建立SSE连接，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
最近有一个新的需求，服务器任务执行完成后需要给客户端发送消息，告诉客户端已经完成这个任务了。用到了SSE（Server Sent Events，服务器发送）。
在Spring中实现SSE连接：
SseEmitterUTF8
解决SSE推送消息乱码的问题，需要继承SseEmitter类，重写里面的extendResponse()，设置响应的类型为TEXT_EVENT_STREAM，并设置字符类型为UTF-8
package com.ruoyi.web.config;import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;import java.nio.charset.StandardCharsets;/*** @Date：2024/4/11 16:09* @description：解决推送消息乱码*/
public class SseEmitterUTF8 extends SseEmitter {public SseEmitterUTF8(Long timeout) {super(timeout);}@Overrideprotected void extendResponse(ServerHttpResponse outputMessage) {super.extendResponse(outputMessage);HttpHeaders headers = outputMessage.getHeaders();headers.setContentType(new MediaType(MediaType.TEXT_EVENT_STREAM, StandardCharsets.UTF_8));}
}SseController
package com.ruoyi.web.controller.order;import com.ruoyi.common.core.domain.AjaxResult;
import com.ruoyi.common.core.domain.model.DownloadCenter;
import com.ruoyi.web.config.SseEmitterUTF8;
import com.ruoyi.web.service.SseService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import javax.annotation.security.PermitAll;/*** @Date：2024/4/11 16:11* @description：SSE*/
@RestController
@RequestMapping("/sse")
public class SseController {@Resourceprivate SseService sseService;/*** 建立连接* @return*/@GetMapping(value = "/connect", produces="text/event-stream;charset=UTF-8")public SseEmitterUTF8 sseConn(String userId){try {SseEmitterUTF8 sseEmitterUTF8 = sseService.connect(userId);return sseEmitterUTF8;} catch (Exception e){e.printStackTrace();throw new RuntimeException("SSE连接异常");}}/*** 给指定的用户发送消息* @param downloadCenter* @return*/@PostMapping("/sendMessage")@PermitAllpublic void sendMessage(String userId){try {sseService.sendMessage(userId);} catch (Exception e){e.printStackTrace();throw new RuntimeException("推送消息异常");}}/*** 断开SSE连接*/@PostMapping("/close")@PermitAllpublic void closeConn(){try {sseService.close();} catch (Exception e){e.printStackTrace();throw new RuntimeException("断开SSE连接异常");}}}
ServiceImpl
package com.ruoyi.web.service.impl;import com.ruoyi.common.constant.CacheConstants;
import com.ruoyi.common.core.domain.AjaxResult;
import com.ruoyi.common.utils.SecurityUtils;
import com.ruoyi.common.utils.StringUtils;
import com.ruoyi.web.config.SseEmitterUTF8;
import com.ruoyi.web.service.SseService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;import javax.annotation.Resource;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;/*** @Date：2024/4/11 16:31* @description：SSE*/
@Service
@Slf4j
public class SseServiceImpl implements SseService {//当前连接数private static AtomicInteger count = new AtomicInteger(0);//所有的SSE连接集合private static Map<String, SseEmitterUTF8> sseEmitterUTF8Map = new ConcurrentHashMap<>();/*** 建立连接* @return*/@Overridepublic SseEmitterUTF8 connect(String userId) throws IOException {//超时时间0表示不过期SseEmitterUTF8 emitter = new SseEmitterUTF8(0L);//注册回调emitter.onCompletion(completionCallBack(userId));emitter.onError(errorCallback(userId));emitter.onTimeout(timeoutCallBack(userId));sseEmitterUTF8Map.put(userId,emitter);//数量+1count.getAndIncrement();log.info("----------------用户{}连接完成----------------",userId);log.info("----------------建立SSE连接的用户数量：{}----------------",sseEmitterUTF8Map.size());return emitter;}/*** 给指定的用户发送消息* @param downloadCenter*/@Overridepublic void sendMessage(String userId) {String message = downloadCenter.getFilename() + "导出完成。";sseEmitterUTF8Map.get(userId).send(map);log.info("----------------消息发送完成：{}----------------",message);} catch (Exception e){log.error("----------------用户 : {}, 返回消息失败 : {}----------------",userId,message);e.printStackTrace();}}/*** 关闭连接*/@Overridepublic void close(String userId) {if (sseEmitterUTF8Map.containsKey(userId)){sseEmitterUTF8Map.get(userId).complete();sseEmitterUTF8Map.remove(userId);log.info("----------------用户{}退出 : {}----------------",userId);}}/*** 判断SSE的连接状态，发哦是那个消息之前可以调用方法判断连接是否有效* @param sseEmitterUTF8* @return*/public static boolean checkSseConnAlive(SseEmitter sseEmitterUTF8){if (Objects.isNull(sseEmitterUTF8)){return false;}// 返回true代表还连接, 返回false代表失去连接return !(Boolean) getField(sseEmitterUTF8,sseEmitterUTF8.getClass(), "sendFailed") &&!(Boolean) getField(sseEmitterUTF8,sseEmitterUTF8.getClass(), "complete");}public static Object getField(Object obj, Class<?> clazz, String fieldName) {for (; clazz != Object.class; clazz = clazz.getSuperclass()) {try {Field field;field = clazz.getDeclaredField(fieldName);field.setAccessible(true);return field.get(obj);} catch (Exception e) {}}return null;}private Runnable timeoutCallBack(String userId) {return () -> {log.error("----------------用户{}连接超时----------------",userId);removeUser(userId);};}private Consumer<Throwable> errorCallback(String userId) {return throwable -> {log.error("----------------用户{}连接异常---" +"-------------",userId);removeUser(userId);};}private static Runnable completionCallBack(String userId){return () -> {log.info("----------------用户{}连接结束----------------",userId);removeUser(userId);};}private static void removeUser(String userId){sseEmitterUTF8Map.remove(userId);count.getAndDecrement();log.info("----------------remove userId : {}----------------",userId);}
}
参考🔗
Spring Boot怎么使用SSE方式向前端推送数据-java教程-PHP中文网
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