What is Spring Session?
Spring is a lightweight, flexible, popular, and widely used application framework for the Java programming language. One benefit of the Spring ecosystem is its modularity and extensibility: Spring includes a wide range of projects and components that you can mix and match to fit your needs during the software development process.
In this article, we’ll discuss one of the components of the Spring ecosystem: Spring Session. But what is Spring Session exactly, and how does Spring Session work?
What is Spring Session?
Managing user state and session is an essential part of any web application. Because the HTTP protocol is stateless, web application developers need to efficiently store and retrieve session data for users.
Spring Session is a component of the Spring framework for managing user session information. The Spring Session component contains the following modules:
- Spring Session Core: This module includes the core functionality and APIs for Spring Session.
- Spring Session Data Redis: This module provides implementations of the SessionRepository and ReactiveSessionRepository classes that can be used with Redis.
- Spring Session JDBC: This module includes support for JDBC, a Java API for connecting to relational databases.
- Spring Session Hazelcast: This module includes compatibility with Hazelcast, an in-memory data store.
In addition to Redis, JDBC, and Hazelcast, Spring Session also includes support for databases and data stores such as MongoDB and Gemfire.
The benefits of Spring Session for user session management include:
- Decoupling the logic of user session management from the application itself.
- Storing user session data in a persistent database, so that it can be recovered if the application crashes.
- Easily switching between database providers (e.g. from Hazelcast to Redis) simply by changing
How does Spring Session work?
Essentially, Spring Session works by reimplementing the HttpServletRequest and HttpSession classes as SessionRepositoryRequestWrapper and HttpSessionWrapper, respectively. Spring Session also provides the SessionRepositoryFilter class, wrapping up the HttpServletRequest inside a SessionRepositoryRequestWrapper.
Spring Session’s HttpSessionWrapper class uses the SessionRepository interface to store information about user sessions. This interface includes methods such as createSession(), deleteById(), findById(), and save() in order to manage your user sessions.
Before using Spring Session, you must update your dependencies. Below is an example of how to add dependencies for Spring Session in Maven if you plan to use the Spring Session Data Redis module:
<dependencies> <dependency> <groupId>org.springframework.session</groupId> <artifactId>spring-session-data-redis</artifactId> </dependency> </dependencies>
Of course, the answer to the question “How does Spring Session work?” will heavily depend on which database backend you want to use with Spring Session. There are multiple tutorials for using Spring Session online. For example, you can check out the Spring framework’s page on Spring Session Data Redis, which includes setup instructions, documentation, and example use cases.
Spring Session and Redis
As mentioned above, Spring Session includes support for Redis via the Spring Session Data Redis module. Redis is an open-source, in-memory data structure store that is widely used to build NoSQL key-value databases, caches, and message brokers.
Because Redis is in-memory, it is an ideal solution for managing user sessions, which often need to be accessed and retrieved very quickly. According to the Redis usage survey, caching and user session management are the top two use cases for Redis.
While Spring Session allows developers to use a Redis backend, however, Redis does not include general support for the Spring framework or the Java programming language. To enjoy the benefits of Redis while programming in Java, many developers have turned to third-party Redis Java clients such as Redisson.
Redisson is a Java client for Redis with a wide variety of features and use cases: scaling, caching, messaging, distributed computing and data processing, microservices, web session clustering, and more.
Below is an example of how to use Redisson with Spring Session:
@Configuration
@EnableRedisHttpSession
public class SessionConfig extends AbstractHttpSessionApplicationInitializer {
@Bean
public RedissonConnectionFactory redissonConnectionFactory(RedissonClient redisson) {
return new RedissonConnectionFactory(redisson);
}
@Bean(destroyMethod = "shutdown")
public RedissonClient redisson(@Value("classpath:/redisson.yaml") Resource configFile) throws IOException {
Config config = Config.fromYAML(configFile.getInputStream());
return Redisson.create(config);
}
}