How does SpringSession count the number of online users through Redis?

Because the original logic of the system is single sign-on using Spring Session plus session sharing by Redis. After logging in, a key value will be set in the session to indicate that the user has logged in, and the HttpServletRequestWrapper will be rewritten to set the remoteUser data value

class RemoteUserRequestWrapper extends HttpServletRequestWrapper {
		String userCode;
		RemoteUserRequestWrapper(HttpServletRequest request) {
			super(request);
			this.userCode = (String) request.getSession()
					.getAttribute(org.apache.commons.lang3.StringUtils.isBlank(sessionKeyName)?DEFAULT_SESSION_KEY_NAME:sessionKeyName);
		}
		@Override
		public String getRemoteUser() {
			return userCode;
		}
	}

Data cached by Spring Session in redis

ThisssoLoginUser key is set when I log in. It is modified according to the business and tested. , when logging out of the system, the session setting expires and the removeAttribute cannot clear the key data in redis, so you can only add the following to the logging out system logic:

Set<String> keys = RedisUtils.redisTemplate.keys("spring:session:sessions:*");
for(String key : keys){
	if(key.indexOf("expires")==-1){
		String s = (String)RedisUtils.redisTemplate.opsForHash().get(key, "sessionAttr:ssoLoginUser");
		if(request.getRemoteUser().equals(s)) {
			logger.info("loginusername:{}",s)
			RedisUtils.redisTemplate.opsForHash().delete(key, "sessionAttr:ssoLoginUser");
		}
	}
}

for data statistics:

  List<Map<String,Object>> list = new ArrayList<Map<String, Object>>();
  List<Map<String,Object>> data = new ArrayList<Map<String, Object>>();
  Set<String> keys = redisTemplate.keys("spring:session:sessions:*");
  for(String key : keys){
      if(key.indexOf("expires")==-1){
          String s = (String)redisTemplate.opsForHash().get(key, "sessionAttr:ssoLoginUser");
          if(StringUtils.isNotBlank(s)) {
              System.out.println(s);
              Map<String,Object> map = new HashMap<String,Object>(16);
              map.put("usercode", s);
              list.add(map);
          }
      }
  }
  return list;

pom .xml：

<dependency>
	<groupId>org.springframework.session</groupId>
	<artifactId>spring-session-data-redis</artifactId>
	<version>1.2.2.RELEASE</version>
	<type>pom</type>
</dependency>

<dependency>
	<groupId>biz.paluch.redis</groupId>
	<artifactId>lettuce</artifactId>
	<version>3.5.0.Final</version>
</dependency>

RedisUtils.java：

package com.common.utils.redis;

import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.web.context.ContextLoader;
import org.springframework.web.context.WebApplicationContext;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.TimeUnit;

public class RedisUtils {

	private RedisUtils() {
	}

	@SuppressWarnings("unchecked")
	public static RedisTemplate<String, Object> redisTemplate =
			ContextLoader.getCurrentWebApplicationContext().getBean(RedisTemplate.class);

	/**
	 * 设置有效时间
	 *
	 * @param key Redis键
	 * @param timeout 超时时间
	 * @return true=设置成功；false=设置失败
	 */
	public static boolean expire(final String key, final long timeout) {

		return expire(key, timeout, TimeUnit.SECONDS);
	}

	/**
	 * 设置有效时间
	 *
	 * @param key Redis键
	 * @param timeout 超时时间
	 * @param unit 时间单位
	 * @return true=设置成功；false=设置失败
	 */
	public static boolean expire(final String key, final long timeout, final TimeUnit unit) {

		Boolean ret = redisTemplate.expire(key, timeout, unit);
		return ret != null && ret;
	}

	/**
	 * 删除单个key
	 *
	 * @param key 键
	 * @return true=删除成功；false=删除失败
	 */
	public static boolean del(final String key) {

		redisTemplate.delete(key);
		return true;
	}

	/**
	 * 删除多个key
	 *
	 * @param keys 键集合
	 * @return 成功删除的个数
	 */
	public static long del(final Collection<String> keys) {

		redisTemplate.delete(keys);
		return 0;
	}

	/**
	 * 存入普通对象
	 *
	 * @param key Redis键
	 * @param value 值
	 */
	public static void set(final String key, final Object value) {

		redisTemplate.opsForValue().set(key, value, 1, TimeUnit.MINUTES);
	}

	// 存储普通对象操作

	/**
	 * 存入普通对象
	 *
	 * @param key 键
	 * @param value 值
	 * @param timeout 有效期，单位秒
	 */
	public static void set(final String key, final Object value, final long timeout) {

		redisTemplate.opsForValue().set(key, value, timeout, TimeUnit.SECONDS);
	}

	/**
	 * 获取普通对象
	 *
	 * @param key 键
	 * @return 对象
	 */
	public static Object get(final String key) {

		return redisTemplate.opsForValue().get(key);
	}

	// 存储Hash操作

	/**
	 * 往Hash中存入数据
	 *
	 * @param key Redis键
	 * @param hKey Hash键
	 * @param value 值
	 */
	public static void hPut(final String key, final String hKey, final Object value) {

		redisTemplate.opsForHash().put(key, hKey, value);
	}

	/**
	 * 往Hash中存入多个数据
	 *
	 * @param key Redis键
	 * @param values Hash键值对
	 */
	public static void hPutAll(final String key, final Map<String, Object> values) {

		redisTemplate.opsForHash().putAll(key, values);
	}

	/**
	 * 获取Hash中的数据
	 *
	 * @param key Redis键
	 * @param hKey Hash键
	 * @return Hash中的对象
	 */
	public static Object hGet(final String key, final String hKey) {

		return redisTemplate.opsForHash().get(key, hKey);
	}

	/**
	 * 获取多个Hash中的数据
	 *
	 * @param key Redis键
	 * @param hKeys Hash键集合
	 * @return Hash对象集合
	 */
	public static List<Object> hMultiGet(final String key, final Collection<Object> hKeys) {

		return redisTemplate.opsForHash().multiGet(key, hKeys);
	}

	// 存储Set相关操作

	/**
	 * 往Set中存入数据
	 *
	 * @param key Redis键
	 * @param values 值
	 * @return 存入的个数
	 */
	public static long sSet(final String key, final Object... values) {
		Long count = redisTemplate.opsForSet().add(key, values);
		return count == null ? 0 : count;
	}

	/**
	 * 删除Set中的数据
	 *
	 * @param key Redis键
	 * @param values 值
	 * @return 移除的个数
	 */
	public static long sDel(final String key, final Object... values) {
		Long count = redisTemplate.opsForSet().remove(key, values);
		return count == null ? 0 : count;
	}

	// 存储List相关操作

	/**
	 * 往List中存入数据
	 *
	 * @param key Redis键
	 * @param value 数据
	 * @return 存入的个数
	 */
	public static long lPush(final String key, final Object value) {
		Long count = redisTemplate.opsForList().rightPush(key, value);
		return count == null ? 0 : count;
	}

	/**
	 * 往List中存入多个数据
	 *
	 * @param key Redis键
	 * @param values 多个数据
	 * @return 存入的个数
	 */
	public static long lPushAll(final String key, final Collection<Object> values) {
		Long count = redisTemplate.opsForList().rightPushAll(key, values);
		return count == null ? 0 : count;
	}

	/**
	 * 往List中存入多个数据
	 *
	 * @param key Redis键
	 * @param values 多个数据
	 * @return 存入的个数
	 */
	public static long lPushAll(final String key, final Object... values) {
		Long count = redisTemplate.opsForList().rightPushAll(key, values);
		return count == null ? 0 : count;
	}

	/**
	 * 从List中获取begin到end之间的元素
	 *
	 * @param key Redis键
	 * @param start 开始位置
	 * @param end 结束位置（start=0，end=-1表示获取全部元素）
	 * @return List对象
	 */
	public static List<Object> lGet(final String key, final int start, final int end) {
		return redisTemplate.opsForList().range(key, start, end);
	}
}

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