spring session实现分布式会话管理

# Spring Session Example This is a small sample project used to demonstrate [Spring Session](http://projects.spring.io/spring-session/). It consists of an Embedded Tomcat that has a single `HelloServlet` servlet. When issuing a `GET` request, the servlet will respond with either the default `Hello World!` or if the `name` session attribute has been set with `Hello [name]`. The `name` session attribute can be changed by issuing a `POST` request with a `name` parameter. For more information, please read my blog post [Scaling out with Spring Session](https://www.jayway.com/2015/05/31/scaling-out-with-spring-session/). ### Redis Download and install [Redis](http://redis.io). For example if you are using OS X you can use Brew, e.g. ```sh $ brew install redis ``` (If you use Linux, you can use `yum` or `apt-get`. Alternatively, read the [Quick Start Guide](http://redis.io/topics/quickstart).) Start Redis by calling the `redis-server` command, e.g. if you use Brew on OS X: ```sh $ redis-server /usr/local/etc/redis.conf [...] Port: 6379 [...] Server started, Redis version 3.0.1 [...] ``` ### 2. Starting a Server Build this project in another terminal: ```sh $ mvn package ``` Start the first Tomcat instance on port 8080 (the default) ```sh $ target/bin/main [...] INFO: Sarting ProtocolHandler ["http-nio-8080"] ``` Check the default, non session, response by issuing a `GET` request: ```sh $ curl http://localhost:8080 Hello World! ``` ### 3. Change the Session State Change the value of the session attribute `name` by issuing a `POST` request with the `name` set as a parameter: ```sh $ curl -i -d "name=Mattias" http://localhost:8080 [...] Set-Cookie: SESSION=12b70435-9e6a-4e67-b544-01394dd59da0; Path=/; HttpOnly [...] ``` Verify that the session attribute has been changed by issuing a `GET` request: ```sh $ curl -H "Cookie: SESSION=12b70435-9e6a-4e67-b544-01394dd59da0" localhost:8080 Hello Mattias! ``` ### 4. Session Replication to a Second Server Start the second Tomcat instance on port 8081: ```sh $ target/bin/main 8081 [...] INFO: Starting ProtocolHandler ["http-nio-8081"] ``` Verify that the session attribute is available by issuing a `GET` request to the other Tomcat: ```sh $ curl -H "Cookie: SESSION=12b70435-9e6a-4e67-b544-01394dd59da0" localhost:8081 Hello Mattias! ``` ### 5. Failover to New Server You can simulate server outage and failover by first shutting down your running servers and then restart a third server: ```sh $ target/bin/main 8082 [...] INFO: Starting ProtocolHandler ["http-nio-8082"] $ curl -H "Cookie: SESSION=12b70435-9e6a-4e67-b544-01394dd59da0" localhost:8082 Hello Mattias! ``` Conclusion, the session state is preserved in all these cases.