This guide describes how to use Spring Session backed by Mongo.

Note
 The completed guide can be found in the mongo sample application.

Updating Dependencies

Before you use Spring Session, you must ensure to update your dependencies. We assume you are working with a working Spring Boot web application. If you are using Maven, ensure to add the following dependencies:

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

	<dependency>
		<groupId>org.springframework.session</groupId>
		<artifactId>spring-session</artifactId>
		<version>2.0.0.RELEASE</version>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-data-mongodb</artifactId>
	</dependency>
</dependencies>

Spring Configuration

After adding the required dependencies, we can create our Spring configuration. The Spring configuration is responsible for creating a Servlet Filter that replaces the HttpSession implementation with an implementation backed by Spring Session.

All you have to do is to add the following Spring Configuration:

Unresolved directive in boot-mongo.adoc - include::https://raw.githubusercontent.com/gregturn/spring-session-data-mongodb-examples/master/spring-session-data-mongodb-traditional-boot/src/main/java/org/springframework/session/mongodb/examples/config/HttpSessionConfig.java[tag=class]

  1. The @EnableMongoHttpSession annotation creates a Spring Bean with the name of springSessionRepositoryFilter that implements Filter. The filter is what is in charge of replacing the HttpSession implementation to be backed by Spring Session. In this instance Spring Session is backed by Mongo.

  2. We explicitly configure JdkMongoSessionConverter since Spring Security’s objects cannot be automatically persisted using Jackson (the default if Jackson is on the classpath).

Configuring the Mongo Connection

Spring Boot automatically creates a MongoClient that connects Spring Session to a Mongo Server on localhost on port 27017 (default port). In a production environment you need to ensure to update your configuration to point to your Mongo server. For example, you can include the following in your application.properties

src/main/resources/application.properties
spring.data.mongodb.host=mongo-srv
spring.data.mongodb.port=27018
spring.data.mongodb.database=prod

For more information, refer to Connecting to MongoDB portion of the Spring Boot documentation.

Servlet Container Initialization

Our Spring 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 (i.e. Tomcat) uses our springSessionRepositoryFilter for every request. Fortunately, Spring Boot takes care of both of these steps for us.

Mongo Sample Application

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

Running the Mongo Sample Application

You can run the sample by obtaining the {download-url}[source code] and invoking the following command:

$ ./gradlew :samples:mongo:bootRun

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

Exploring the security Sample Application

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 your are logged in with the user entered previously. The user’s information is stored in Mongo rather than Tomcat’s HttpSession implementation.

How does it work?

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

When a new HttpSession is created, Spring Session creates a cookie named SESSION in your browser that contains the id of your session. Go ahead and view the cookies (click for help with Chrome or Firefox).

If you like, you can easily inspect the session using mongo client. For example, on a Linux based system you can type:

Note

The sample application uses an embedded MongoDB instance that listens on a randomly allocated port. The port used by embedded MongoDB together with exact command to connect to it is logged during application startup.

 
$ mongo --port ...
> use test
> db.sessions.find().pretty()

Alternatively, you can also delete the explicit key. Enter the following into your terminal ensuring to replace 60f17293-839b-477c-bb92-07a9c3658843 with the value of your SESSION cookie:

> db.sessions.remove({"_id":"60f17293-839b-477c-bb92-07a9c3658843"})

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