Springboot+jwt实现在线用户功能(示例代码)

package com.example.demo.config;
import org.springframework.stereotype.Component;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/*
* 在线用户
* */
@Component
public class OnlineCounter {
    private static Map countMap = new ConcurrentHashMap<String,Object>();
    public void insertToken(String token){
        //获取当前时间（毫秒）
        //解析token
        String userId = TokenUtil.getUserId(token);
        countMap.put(userId,token);
    }
    /*
    * 获取当前在线总数
    * */
    public Integer getOnlineCount(){
        int onlineCount = 0;
        //获取countMap的迭代器
        Iterator iterator = countMap.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry<String,Object> entry = (Map.Entry<String,Object>) iterator.next();
            String token = (String) entry.getValue();
            boolean flag = TokenUtil.hasExpiresAt(token);//返回true就是过期了
            if(flag){
                //移除
                countMap.remove(entry.getKey());
            }else{
                onlineCount++;
            }
        }
        return onlineCount;
    }
    /*
    * 获取当前在线用户列表
    * */
    public List<String> getOnlineUserList(){
        List<String> userIdList = new ArrayList<>();
        //获取countMap的迭代器
        Iterator iterator = countMap.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry<String,Object> entry = (Map.Entry<String,Object>) iterator.next();
            String token = (String) entry.getValue();
            boolean flag = TokenUtil.hasExpiresAt(token);//返回true就是过期了
            if(flag){
                //移除
                countMap.remove(entry.getKey());
            }else{
                userIdList.add(entry.getKey());
            }
        }
        return userIdList;
    }
}

@component
public class JWTInterceptor implements HandlerInterception{
    @Autowired
    private OnlineCounter onlineCounter;
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (!handler.getClass().isAssignableFrom(HandlerMethod.class)) {
            return true;
        } else {
			//jwt业务逻辑代码。。。。。。           
			//记录在线人员
            onlineCounter.insertUser(userId);
            return true;
        }
    }
}

/*
    * 根据token判断是否过期
    * */
    public static boolean hasExpiresAt(String token){
        //创建token验证器
        try{
            JWTVerifier jwtVerifier=JWT.require(Algorithm.HMAC256(TOKEN_SECRET)).withIssuer("auth0").build();
            DecodedJWT decodedJWT=jwtVerifier.verify(token);
            Date timeoutDate = decodedJWT.getExpiresAt();//获取过期时间
            long diffTime = timeoutDate.getTime() - new Date().getTime();//获取过期时间与当前时间的时间差（毫秒）
            System.out.println("过期时间与当前时间的时间差（毫秒）:"+diffTime);
            if(diffTime < 0){
                //已过期
                return true;
            }else{
                //未过期
                return false;
            }
        }catch (Exception e){
            return true;
        }
    }

@ApiController(value = "/sys/online")
public class OnlineController {
    @Autowired
    private OnlineCounter onlineCounter;
    /**
     * 获取当前用户在线人数
     *
     * @return
     */
    @GetMapping(value = "/getOnlineCount")
    public int getRealOnlineCount() {
        Integer onlines = onlineCounter.getOnlineCount();
        return onlines;
    }
}