In web applications, there are always data needed to be stored in http session. Java uses
javax.servlet.http.HttpSession class for this. But this interface also needs implementation,
which will take data we want in session, bind it with some unique session identifier, and store it in memory
or on disc for later usage.
This implementation is usually web container specific. As the most java web applications use Tomcat as container, there this concept is known as Session management component and implemented in
This usually works well. Especially if you run it on local machine with single Tomcat server
instance, during development. But problem might arise in production. Web container might not be Tomcat, but some
other servlet, Java EE or web profile implementation. In cloud environments, there can be multiple server instances
where our web application is deployed. Requests from one user should be served from the same instance, but for various
reasons this may be not the case.
All this leads to lost session data. Which is also hard to spot, as everything works well in local environment. And there are no server errors, just HttpSession attributes are not there. This happened to me with Openshift online cloud environment. Hence, I applied approach described here and solved the problem.
As with many other things, guys from Spring recognized this problem and came with unified neat solution. It's
Spring Session project. I already use Spring as basic app
container and web mvc framework, so using Spring Session introduces little changes.
And as sessions need to be stored in some kind of data management tool, Spring chose Redis for this.
All the wiring and configuration is explained
It's all well explained, but if you run into problems making everything work as I did, here are few hints:
JedisConnectionFactorydescribed in article above must also be configured to use specific port and host. It should be configured like this
<bean class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory" p:hostName="127.8.1.1" p:port="12345" p:password="ZTNdevwerGW#RGWRGwergw" />