Spring Session - Spring Boot

This guide describes how to use Spring Session to transparently leverage Redis to back a web application’s HttpSession when you use Spring Boot.

You can find the completed guide in the boot sample application.

Updating Dependencies

Before you use Spring Session with Redis, you must ensure that you have the right dependencies. We assume you are working with a working Spring Boot web application.

pom.xml
<dependencies>
	<!-- ... -->

	<dependency>
		<groupId>org.springframework.session</groupId>
		<artifactId>spring-session-data-redis</artifactId>
	</dependency>
</dependencies>
build.gradle
implementation("org.springframework.session:spring-session-data-redis")

Spring Boot provides dependency management for Spring Session modules, so you need not explicitly declare dependency version.

Spring Boot Configuration

After adding the required dependencies, we can create our Spring Boot configuration. Thanks to first-class auto-configuration support, just by adding the dependency Spring Boot will set up Spring Session backed by Redis for us.

Under the hood, Spring Boot applies configuration that is equivalent to manually adding @EnableRedisHttpSession annotation. This creates a Spring bean with the name of springSessionRepositoryFilter that implements Filter. The filter is in charge of replacing the HttpSession implementation to be backed by Spring Session.

Further customization is possible by using application.properties, as the following listing shows:

src/main/resources/application.properties
server.servlet.session.timeout= # Session timeout. If a duration suffix is not specified, seconds is used.
spring.session.redis.flush-mode=on_save # Sessions flush mode.
spring.session.redis.namespace=spring:session # Namespace for keys used to store sessions.

For more information, see the Spring Session portion of the Spring Boot documentation.

Configuring the Redis Connection

Spring Boot automatically creates a RedisConnectionFactory that connects Spring Session to a Redis Server on localhost on port 6379 (default port). In a production environment, you need to update your configuration to point to your Redis server. For example, you can include the following in your application.properties:

src/main/resources/application.properties
spring.data.redis.host=localhost # Redis server host.
spring.data.redis.password= # Login password of the redis server.
spring.data.redis.port=6379 # Redis server port.

For more information, see the Connecting to Redis portion of the Spring Boot documentation.

Servlet Container Initialization

Our Spring Boot Configuration created a Spring bean named springSessionRepositoryFilter that implements Filter. The springSessionRepositoryFilter bean is responsible for replacing the HttpSession with a custom implementation that is backed by Spring Session.

In order for our Filter to do its magic, Spring needs to load our Config class. Last, we need to ensure that our servlet container (that is, Tomcat) uses our springSessionRepositoryFilter for every request. Fortunately, Spring Boot takes care of both of these steps for us.

Boot Sample Application

The Boot Sample Application demonstrates how to use Spring Session to transparently leverage Redis to back a web application’s HttpSession when you use Spring Boot.

Running the Boot Sample Application

You can run the sample by obtaining the source code and invoking the following command:

$ ./gradlew :spring-session-sample-boot-redis:bootRun
For the sample to work, you must install Redis 2.8+ on localhost and run it with the default port (6379). Alternatively, you can update the RedisConnectionFactory to point to a Redis server. Another option is to use Docker to run Redis on localhost. See Docker Redis repository for detailed instructions.

You should now be able to access the application at localhost:8080/

Exploring the security Sample Application

Now you can try using the application. Enter the following to log in:

  • Username user

  • Password password

Now click the Login button. You should now see a message indicating you are logged in with the user entered previously. The user’s information is stored in Redis rather than Tomcat’s HttpSession implementation.

How Does It Work?

Instead of using Tomcat’s HttpSession, we persist the values in Redis. Spring Session replaces the HttpSession with an implementation that is backed by Redis. When Spring Security’s SecurityContextPersistenceFilter saves the SecurityContext to the HttpSession, it is then persisted into Redis.

When a new HttpSession is created, Spring Session creates a cookie named SESSION in your browser. That cookie contains the ID of your session. You can view the cookies (with Chrome or Firefox).

You can remove the session by using redis-cli. For example, on a Linux based system you can type the following:

	$ redis-cli keys '*' | xargs redis-cli del
The Redis documentation has instructions for installing redis-cli.

Alternatively, you can also delete the explicit key. To do so, enter the following into your terminal, being sure to replace 7e8383a4-082c-4ffe-a4bc-c40fd3363c5e with the value of your SESSION cookie:

	$ redis-cli del spring:session:sessions:7e8383a4-082c-4ffe-a4bc-c40fd3363c5e

Now you can visit the application at localhost:8080/ and observe that we are no longer authenticated.