= Spring Session - Custom Cookie
Rob Winch
:toc:

This guide describes how to configure Spring Session to use custom cookies with Java Configuration.
The guide assumes you have already link:./httpsession.html[setup Spring Session in your project].

NOTE: The completed guide can be found in the <<custom-cookie-sample, Custom Cookie sample application>>.

[[custom-cookie-spring-configuration]]
== Spring Java Configuration

Once you have setup Spring Session you can easily customize how the session cookie is written by exposing a `CookieSerializer` as a Spring Bean.
Out of the box, Spring Session comes with `DefaultCookieSerializer`.
Simply exposing the `DefaultCookieSerializer` as a Spring Bean will augment the existing configuration when using configurations like `@EnableRedisHttpSession`.
You can find an example of customizing Spring Session's cookie below:

[source,java]
----
include::{samples-dir}javaconfig/custom-cookie/src/main/java/sample/Config.java[tags=cookie-serializer]
----

<1> We customize the name of the cookie to be JSESSIONID
<2> We customize the path of the cookie to be "/" (rather than the default of the context root)
<3> We customize the domain name pattern (a regular expression) to be `^.+?\\.(\\w+\\.[a-z]+)$`
This allows sharing a session across domains and applications.
If the regular expression does not match, no domain is set and the existing domain will be used.
If the regular expression matches, the first https://docs.oracle.com/javase/tutorial/essential/regex/groups.html[grouping] will be used as the domain.
This means that a request to https://child.example.com will set the domain to example.com.
However, a request to http://localhost:8080/ or http://192.168.1.100:8080/ will leave the cookie unset and thus still work in development without any changes necessary for production.

[WARNING]
====
It is important to note that users should only match on valid domain characters since the domain name is reflected in the response.
This is prevent a malicious user from performing attacks like https://en.wikipedia.org/wiki/HTTP_response_splitting[HTTP Response Splitting].
====

[[custom-cookie-options]]
== Configuration Options

The configuration options available are:

* `cookieName` - the name of the cookie to use
Default "SESSION"
* `useSecureCookie` - specify if a secure cookie be used
Default use value of `HttpServletRequest.isSecure()` at the time of creation.
* `cookiePath` - the path of the cookie
Default is context root
* `cookieMaxAge` - specifies the max age of the cookie to be set at the time the session is created.
Default is -1 which indicates the cookie will be removed when the browser is closed.
* `jvmRoute` - specifies a suffix to be appended to the session id and included in the cookie.
Used to identify which JVM to route to for session affinity.
With some implementations (i.e. Redis) this provides no performance benefit.
However, this can help with tracing logs of a particular user.
* `domainName` - allows specifying a specific domain name to be used for the cookie.
This option is simple to understand, but will likely require a different configuration between development and production environments.
See domainNamePattern as an alternative.
* `domainNamePattern` - a case insensitive pattern used to extract the domain name from the `HttpServletRequest#getServerName()`.
The pattern should provide a single grouping used to extract the value of the cookie domain.
If the regular expression does not match, no domain is set and the existing domain will be used.
If the regular expression matches, the first https://docs.oracle.com/javase/tutorial/essential/regex/groups.html[grouping] will be used as the domain.

[WARNING]
====
It is important to note that users should only match on valid domain characters since the domain name is reflected in the response.
This is prevent a malicious user from performing attacks like https://en.wikipedia.org/wiki/HTTP_response_splitting[HTTP Response Splitting].
====


[[custom-cookie-sample]]
== custom-cookie Sample Application



=== Running the custom-cookie Sample Application

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

[NOTE]
====
For the sample to work, you must http://redis.io/download[install Redis 2.8+] on localhost and run it with the default port (6379).
Alternatively, you can update the `LettuceConnectionFactory` to point to a Redis server.
====

----
$ ./gradlew :samples:custom-cookie:tomcatRun
----

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

=== Exploring the custom-cookie 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.

If you look at the cookies for the application, you can see the cookie is saved to the custom name of JSESSIONID
