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This article introduces the knowledge of "how to use Spring Session to solve the problem of distributed session sharing in SpringBoot". Many people will encounter this dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Preface

If you are using Java to develop Web applications, you must be familiar with HttpSession, but we know that HpptSession uses memory to manage Session by default, and if you scale out the application, there will be Session sharing problems.

Spring Session provides a solution for creating and managing Servlet HttpSession to solve the problem of Session sharing, and more importantly, it is extremely easy to use in Spring Boot.

Problems with Session sharing

HttpSession is created and managed through Servlet containers, such as Tomcat/Jetty, which are stored in memory. If we build a distributed cluster with the scale-out of Web applications, and then use LVS or Nginx for load balancing, it is possible that Http requests from the same user will be distributed to two different instances. How to ensure Session sharing between different instances has become a problem that has to be solved.

The simplest solution is to save the Session data in a unified place outside of memory, such as Memcached/Redis. So the question comes again, how do you replace the Servlet container's implementation of creating and managing HttpSession?

Make use of the plug-in function provided by the Servlet container to customize the creation and management policy of HttpSession and replace the default policy by configuration. The drawback of this approach, however, is that you need to couple the code of Servlet containers such as Tomcat/Jetty. In fact, there have long been open source projects in this area, such as memcached-session-manager and tomcat-redis-session-manager. Only Tomcat6/Tomcat7 is supported for the time being.

two。 Configure the load balancing algorithm of Nginx to ip_hash, so that each request is allocated according to the hash result of accessing IP, so that visitors from the same IP regularly access a back-end server, which effectively solves the problem of Session sharing in dynamic web pages.

3. If you use Shiro to manage Session, you can use Redis to implement the SessionDao interface of Shiro, so that Session is held by Redis.

4. Design a Filter, use HttpServletRequestWrapper, implement your own getSession () method, and take over the work of creating and managing Session data. Spring-Session is realized through this way of thinking.

Integrate Spring Session in Spring Boot

Spring Session supports using Redis, Mongo, JDBC, and Hazelcast to store Session. Here, take Redis as an example.

1. Introduce Maven dependency (dependencyManagement is used in this example, please add tags if you don't use it)

Org.springframework.boot spring-boot-starter-data-redis org.springframework.session spring-session

2. Configure your Spring Application and add your application.properties to the following configuration.

Spring.session.store-type=redis

With these two steps alone, the integration is completed, and the whole process is completely painless and senseless.

Note: if your Redis server does not use the local default configuration (localhost:6379), you need to configure your Redis, how to configure it? Look at here.

Let's verify it.

Sure enough, Http Session has been packaged by Spring Session, and we can still use Http Session's API to program.

Cookies is also created normally, and Key is SESSION.

127.0.0.1 480c-8b88-eafc798e7269 6379 > keys * 1) "spring:session:sessions:083706a8-b2d8-480c-8b88-eafc798e7269" 2) "spring:session:sessions:expires:083706a8-b2d8-480c-8b88-eafc798e7269" 3) "spring:session:expirations:1490263320000"

Using redis-cli to view, it is found that the relevant data has also been saved in Redis.

That's all for "how to use Spring Session to solve distributed session sharing problems in SpringBoot". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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