Cleanup Antora
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Rob Winch
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spring-session-docs/modules/ROOT/pages/guides/java-redis.adoc
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spring-session-docs/modules/ROOT/pages/guides/java-redis.adoc
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= Spring Session - HttpSession (Quick Start)
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Rob Winch
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:toc: left
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:version-snapshot: true
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:stylesdir: ../
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:highlightjsdir: ../js/highlight
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:docinfodir: guides
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This guide describes how to use Spring Session to transparently leverage Redis to back a web application's `HttpSession` with Java Configuration.
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NOTE: You can find the completed guide in the <<httpsession-sample, httpsession sample application>>.
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[#index-link]
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link:../index.html[Index]
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== Updating Dependencies
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Before you use Spring Session, you must update your dependencies.
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If you are using Maven, you must add the following dependencies:
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====
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.pom.xml
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[source,xml]
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[subs="verbatim,attributes"]
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----
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<dependencies>
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<!-- ... -->
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<dependency>
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<groupId>org.springframework.session</groupId>
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<artifactId>spring-session-data-redis</artifactId>
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<version>{spring-session-version}</version>
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<type>pom</type>
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</dependency>
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<dependency>
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<groupId>io.lettuce</groupId>
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<artifactId>lettuce-core</artifactId>
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<version>{lettuce-version}</version>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-web</artifactId>
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<version>{spring-framework-version}</version>
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</dependency>
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</dependencies>
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----
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====
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ifeval::["{version-snapshot}" == "true"]
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Since we are using a SNAPSHOT version, we need to ensure to add the Spring Snapshot Maven Repository.
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You must have the following in your pom.xml:
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====
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.pom.xml
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[source,xml]
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----
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<repositories>
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<!-- ... -->
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<repository>
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<id>spring-snapshot</id>
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<url>https://repo.spring.io/libs-snapshot</url>
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</repository>
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</repositories>
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----
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====
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endif::[]
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ifeval::["{version-milestone}" == "true"]
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Since we are using a Milestone version, we need to ensure to add the Spring Milestone Maven Repository.
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You must have the following in your pom.xml:
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====
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.pom.xml
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[source,xml]
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----
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<repository>
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<id>spring-milestone</id>
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<url>https://repo.spring.io/libs-milestone</url>
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</repository>
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----
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====
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endif::[]
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// tag::config[]
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[[httpsession-spring-configuration]]
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== Spring Java Configuration
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After adding the required dependencies, we can create our Spring configuration.
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The Spring configuration is responsible for creating a servlet filter that replaces the `HttpSession` implementation with an implementation backed by Spring Session.
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To do so, add the following Spring Configuration:
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====
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[source,java]
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----
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include::{samples-dir}spring-session-sample-javaconfig-redis/src/main/java/sample/Config.java[tags=class]
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----
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<1> The `@EnableRedisHttpSession` annotation creates a Spring Bean with the name of `springSessionRepositoryFilter` that implements `Filter`.
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The filter is in charge of replacing the `HttpSession` implementation to be backed by Spring Session.
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In this instance, Spring Session is backed by Redis.
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<2> We create a `RedisConnectionFactory` that connects Spring Session to the Redis Server.
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We configure the connection to connect to localhost on the default port (6379).
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For more information on configuring Spring Data Redis, see the https://docs.spring.io/spring-data/data-redis/docs/{spring-data-redis-version}/reference/html/[reference documentation].
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====
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== Java Servlet Container Initialization
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Our <<httpsession-spring-configuration,Spring Configuration>> created a Spring Bean named `springSessionRepositoryFilter` that implements `Filter`.
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The `springSessionRepositoryFilter` bean is responsible for replacing the `HttpSession` with a custom implementation that is backed by Spring Session.
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In order for our `Filter` to do its magic, Spring needs to load our `Config` class.
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Last, we need to ensure that our Servlet Container (that is, Tomcat) uses our `springSessionRepositoryFilter` for every request.
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Fortunately, Spring Session provides a utility class named `AbstractHttpSessionApplicationInitializer` to make both of these steps easy.
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The following shows an example:
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====
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.src/main/java/sample/Initializer.java
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[source,java]
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----
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include::{samples-dir}spring-session-sample-javaconfig-redis/src/main/java/sample/Initializer.java[tags=class]
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----
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NOTE: The name of our class (`Initializer`) does not matter. What is important is that we extend `AbstractHttpSessionApplicationInitializer`.
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<1> The first step is to extend `AbstractHttpSessionApplicationInitializer`.
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Doing so ensures that the Spring Bean by the name of `springSessionRepositoryFilter` is registered with our Servlet Container for every request.
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<2> `AbstractHttpSessionApplicationInitializer` also provides a mechanism to ensure Spring loads our `Config`.
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====
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// end::config[]
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[[httpsession-sample]]
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== httpsession Sample Application
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=== Running the `httpsession` Sample Application
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You can run the sample by obtaining the {download-url}[source code] and invoking the following command:
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====
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----
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$ ./gradlew :spring-session-sample-javaconfig-redis:tomcatRun
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----
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====
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NOTE: For the sample to work, you must https://redis.io/download[install Redis 2.8+] on localhost and run it with the default port (6379).
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Alternatively, you can update the `RedisConnectionFactory` to point to a Redis server.
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Another option is to use https://www.docker.com/[Docker] to run Redis on localhost.
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See https://hub.docker.com/_/redis/[Docker Redis repository] for detailed instructions.
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You should now be able to access the application at http://localhost:8080/
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=== Exploring the `httpsession` Sample Application
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Now you can try to use the application. To do so, fill out the form with the following information:
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* *Attribute Name:* _username_
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* *Attribute Value:* _rob_
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Now click the *Set Attribute* button. You should now see the values displayed in the table.
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=== How Does It Work?
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We interact with the standard `HttpSession` in the `SessionServlet` shown in the following listing:
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====
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.src/main/java/sample/SessionServlet.java
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[source,java]
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----
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include::{samples-dir}spring-session-sample-javaconfig-redis/src/main/java/sample/SessionServlet.java[tags=class]
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----
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====
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Instead of using Tomcat's `HttpSession`, we persist the values in Redis.
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Spring Session creates a cookie named `SESSION` in your browser.
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That cookie contains the ID of your session.
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You can view the cookies (with https://developers.google.com/web/tools/chrome-devtools/manage-data/cookies[Chrome] or https://developer.mozilla.org/en-US/docs/Tools/Storage_Inspector[Firefox]).
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You can remove the session by using redis-cli.
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For example, on a Linux based system you can type the following:
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====
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----
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$ redis-cli keys '*' | xargs redis-cli del
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----
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====
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TIP: The Redis documentation has instructions for https://redis.io/topics/quickstart[installing redis-cli].
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Alternatively, you can also delete the explicit key. Enter the following into your terminal, being sure to replace `7e8383a4-082c-4ffe-a4bc-c40fd3363c5e` with the value of your SESSION cookie:
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====
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----
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$ redis-cli del spring:session:sessions:7e8383a4-082c-4ffe-a4bc-c40fd3363c5e
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----
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====
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Now you can visit the application at http://localhost:8080/ and see that the attribute we added is no longer displayed.
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