This guide describes how to use Spring Session to transparently leverage a relational database to back a web application’s HttpSession with Java Configuration.

The completed guide can be found in the httpsession-jdbc sample application.

Updating Dependencies

Before you use Spring Session, you must ensure to update your dependencies. If you are using Maven, ensure to add the following dependencies:

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

        <dependency>
                <groupId>org.springframework.session</groupId>
                <artifactId>spring-session-jdbc</artifactId>
                <version>1.2.0.RC2</version>
                <type>pom</type>
        </dependency>
        <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-web</artifactId>
                <version>4.2.5.RELEASE</version>
        </dependency>
</dependencies>

Since We are using a Milestone version, we need to ensure to add the Spring Milestone Maven Repository. Ensure you have the following in your pom.xml:

pom.xml
<repository>
        <id>spring-milestone</id>
        <url>https://repo.spring.io/libs-milestone</url>
</repository>

Spring Java 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. Add the following Spring Configuration:

@EnableJdbcHttpSession (1)
public class Config {

        @Bean
        public EmbeddedDatabase dataSource() {
                return new EmbeddedDatabaseBuilder() (2)
                                .setType(EmbeddedDatabaseType.H2)
                                .addScript("org/springframework/session/jdbc/schema-h2.sql").build();
        }

        @Bean
        public PlatformTransactionManager transactionManager(DataSource dataSource) {
                return new DataSourceTransactionManager(dataSource); (3)
        }

}
1 The @EnableJdbcHttpSession 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 a relational database.
2 We create a dataSource that connects Spring Session to an embedded instance of H2 database. We configure the H2 database to create database tables using the SQL script which is included in Spring Session.
3 We create a transactionManager that manages transactions for previously configured dataSource.

Java 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 Session provides a utility class named AbstractHttpSessionApplicationInitializer both of these steps extremely easy. You can find an example below:

src/main/java/sample/Initializer.java
public class Initializer extends AbstractHttpSessionApplicationInitializer { (1)

        public Initializer() {
                super(Config.class); (2)
        }
}
The name of our class (Initializer) does not matter. What is important is that we extend AbstractHttpSessionApplicationInitializer.
1 The first step is to extend AbstractHttpSessionApplicationInitializer. This ensures that the Spring Bean by the name springSessionRepositoryFilter is registered with our Servlet Container for every request.
2 AbstractHttpSessionApplicationInitializer also provides a mechanism to easily ensure Spring loads our Config.

httpsession-jdbc Sample Application

Running the httpsession-jdbc Sample Application

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

$ ./gradlew :samples:httpsession-jdbc:tomcatRun

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

Exploring the httpsession-jdbc Sample Application

Try using the application. Fill out the form with the following information:

  • Attribute Name: username

  • Attribute Value: rob

Now click the Set Attribute button. You should now see the values displayed in the table.

How does it work?

We interact with the standard HttpSession in the SessionServlet shown below:

src/main/java/sample/SessionServlet.java
@WebServlet("/session")
public class SessionServlet extends HttpServlet {

        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                        throws ServletException, IOException {
                String attributeName = req.getParameter("attributeName");
                String attributeValue = req.getParameter("attributeValue");
                req.getSession().setAttribute(attributeName, attributeValue);
                resp.sendRedirect(req.getContextPath() + "/");
        }

        private static final long serialVersionUID = 2878267318695777395L;
}

Instead of using Tomcat’s HttpSession, we are actually persisting the values in H2 database. 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 remove the session using H2 web console available at: http://localhost:8080/h2-console/ (use jdbc:h2:mem:testdb for JDBC URL)

Now visit the application at http://localhost:8080/ and observe that the attribute we added is no longer displayed.