A preliminary study of spring-session one of spring-session

1. What is spring-session

1.1 Background - session session sharing

HttpSessionIt is created and managed by the servlet container, like Tomcat/Jetty is stored in memory.
But if we build the application into a distributed cluster and use LVS or Nginx to do it 负载均衡, then Http requests from the same user will likely be distributed to two different applications.

The question is , how to ensure that different web sites can share the same session data?

The simplest idea is to save the session data to a unified place outside the memory, such as Memcached/Redis and other databases.
Then the question comes again , how to replace the implementation of Servlet container creation and management HttpSession?

Use the Servlet container to 插件功能customize the creation and management strategy of HttpSession, and replace the default strategy by configuration.

In fact, there have already been open source projects in this regard, such as memcached-session-manager(currently our official mall uses this), and tomcat-redis-session-manager.
However, this method has a disadvantage, that is, it needs to couple the code of Servlet containers such as Tomcat/Jetty.
Design a Filter, 利用HttpServletRequestWrapperimplement your own getSession() method, and take over the work of creating and managing Session data. spring-sessionIt is through this way of thinking.

1.2 `spring-session`Introduction

spring-session is one of Spring's projects,

Official website address: http://projects.spring.io/spring-session/
GitHub address: https://github.com/spring-projects/spring-session

spring-session Provides a set of solutions for creating and managing Servlet HttpSession. spring-session Provides the clustered Session (Clustered Sessions) function. By default, external Redis is used to store Session data to solve the problem of Session sharing.

The following is a feature introduction from the official website:

Spring Session provides the following features:

API and implementations for managing a user's session

HttpSession - allows replacing the HttpSession in an application container (i.e. Tomcat) neutral way

Clustered Sessions - Spring Session makes it trivial to support clustered sessions without being tied to an application container specific solution.

Multiple Browser Sessions - Spring Session supports managing multiple users' sessions in a single browser instance (i.e. multiple authenticated accounts similar to Google).

RESTful APIs - Spring Session allows providing session ids in headers to work with RESTful APIs

WebSocket - provides the ability to keep the HttpSession alive when receiving WebSocket messages

2. Self-study source code usage (take redis as an example)

Steps (refer to http://docs.spring.io/spring-session/docs/current/reference/html5/guides/httpsession.html ):

First download the source code from GitHub https://github.com/spring-projects/spring-session
Local installation gradle (omitted), refer to http://feitianbenyue.iteye.com/blog/2326268
Install locally redis (need 2.8+) and start (omitted)
Based on spring-session the root directory, execute gradlew :samples:httpsession-xml:tomcatRun

Then you can open http://localhost:8080, you can see the following interface, and you can use this page to set the session attribute

3. The key in redis

open redis-cli, enter

keys *

result:

It can be seen that redis the spring-session relevant key in it spring:session: starts with

and has the following keys

127.0.0.1:6379> keys spr*
1) "spring:session:expirations:1474542840000"
2) "spring:session:sessions:c3ae0dba-058e-4eca-99ad-6ec5225fd6e0"
3) "spring:session:sessions:expires:c3ae0dba-058e-4eca-99ad-6ec5225fd6e0"

至此,我们大概知道 spring-session 是什么东东, 大概怎么玩, 下面我们来聊聊项目中如何使用他

4.参考

---to be continued