Spring boot集成Redis实现sessions共享时，sessions过期时间问题分析

Springboot鼓励零配置的方式，帮你做好大部分重复劳动的事，好到不能再好；具体的Redis安装方法和Springboot集成Redis方法，可以去搜索相关文章或参考该文。

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@EnableRedisHttpSession(maxInactiveIntervalInSeconds= 3600,redisNamespace = "tl")
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public class RedisSessionConfig {
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}

org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession注解，该注解的解析类为：
org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration；可以看到
maxInactiveIntervalInSeconds默认值为1800秒，找到setImportMetadata函数：

 
public void setImportMetadata(AnnotationMetadata importMetadata) {
 
 
 
Map<String, Object> enableAttrMap = importMetadata
 
.getAnnotationAttributes(EnableRedisHttpSession.class.getName());
 
AnnotationAttributes enableAttrs = AnnotationAttributes.fromMap(enableAttrMap);
 
/**
 
*解析注解，获取maxInactiveIntervalInSeconds赋值给配置类的maxInactiveIntervalInSeconds对象
 
*/
 
this.maxInactiveIntervalInSeconds = enableAttrs
 
.getNumber("maxInactiveIntervalInSeconds");
 
String redisNamespaceValue = enableAttrs.getString("redisNamespace");
 
/**
 
*设置命名空间
 
*/
 
if (StringUtils.hasText(redisNamespaceValue)) {
 
this.redisNamespace = this.embeddedValueResolver.resolveStringValue(redisNamespaceValue);
 
}
 
this.redisFlushMode = enableAttrs.getEnum("redisFlushMode");
 
}

	利用Redis作为sessions共享仓实现类为org.springframework.session.data.redis.RedisOperationsSessionRepository
其执行session过期策略的实现类为RedisSessionExpirationPolicy，其过期的具体函数如下：
 
public void onExpirationUpdated(Long originalExpirationTimeInMilli,
 
ExpiringSession session) {
 
String keyToExpire = "expires:" + session.getId();
 
long toExpire = roundUpToNextMinute(expiresInMillis(session));
 
 
 
if (originalExpirationTimeInMilli != null) {
 
long originalRoundedUp = roundUpToNextMinute(originalExpirationTimeInMilli);
 
if (toExpire != originalRoundedUp) {
 
String expireKey = getExpirationKey(originalRoundedUp);
 
this.redis.boundSetOps(expireKey).remove(keyToExpire);
 
}
 
}
 
 
 
long sessionExpireInSeconds = session.getMaxInactiveIntervalInSeconds();
 
String sessionKey = getSessionKey(keyToExpire);
 
 
 
if (sessionExpireInSeconds < 0) {
 
this.redis.boundValueOps(sessionKey).append("");
 
this.redis.boundValueOps(sessionKey).persist();
 
this.redis.boundHashOps(getSessionKey(session.getId())).persist();
 
return;
 
}
 
 
 
String expireKey = getExpirationKey(toExpire);
 
BoundSetOperations<Object, Object> expireOperations = this.redis
 
.boundSetOps(expireKey);
 
expireOperations.add(keyToExpire);
 
/**
 
*关键在此处，在设置的基础上增加了5分钟
 
/
 
long fiveMinutesAfterExpires = sessionExpireInSeconds
 
+ TimeUnit.MINUTES.toSeconds(5);
 
 
 
expireOperations.expire(fiveMinutesAfterExpires, TimeUnit.SECONDS);
 
if (sessionExpireInSeconds == 0) {
 
this.redis.delete(sessionKey);
 
}
 
else {
 
this.redis.boundValueOps(sessionKey).append("");
 
this.redis.boundValueOps(sessionKey).expire(sessionExpireInSeconds,
 
TimeUnit.SECONDS);
 
}
 
this.redis.boundHashOps(getSessionKey(session.getId()))
 
.expire(fiveMinutesAfterExpires, TimeUnit.SECONDS);
 
}