:version: 2.2.8.RELEASE
:geode-version: 19

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= Spring Session for Apache Geode & VMware Tanzu GemFire

_Spring Session_ core provides an API along with several provider implementations to manage user sessions.  It also
simplifies the support for clustered session state management without being tied to an application container
specific solution.

Out of the box _Spring Session_ provides integration with:

* `HttpSession` - replaces the `HttpSession` supplied by the application container (e.g. Apache Tomcat)
in a neutral way along with providing HTTP Session IDs in the HTTP Header to work with REST APIs.

* `WebSocket` - keeps the `HttpSession` active when receiving WebSocket messages.

On top of the core _Spring Session_ features, _Spring Session for Apache Geode and Pivotal GemFire_ (SSDG) positions
either https://geode.apache.org/[Apache Geode] or https://pivotal.io/pivotal-gemfire[Pivotal GemFire]
as a session repository provider and adds additional capabilities required by enterprise class solutions:

* Custom `Expiration Policies` - in addition to the default, 30 minute session _idle expiration timeout_ (TTI), which
is configurable, SSDG also supports _fixed-duration expiration timeout_ (e.g. expire the session after 1 hour
regardless of whether the session is active or inactive).  Users may also define custom expiration policies using the
https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/{version}/api/org/springframework/session/data/gemfire/expiration/SessionExpirationPolicy.html[`SessionExpirationPolicy`] interface.
See the https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/{version}/reference/html5/#httpsession-gemfire-expiration[documentation] for more details.

* Custom `Data Serialization` - in addition to the default Apache Geode https://geode.apache.org/docs/guide/{geode-version}/developing/data_serialization/gemfire_pdx_serialization.html[PDX Serialization] format,
users may configure Apache Geode https://geode.apache.org/docs/guide/{geode-version}/developing/data_serialization/gemfire_data_serialization.html[Data Serialization]
with full support for https://geode.apache.org/docs/guide/{geode-version}/developing/delta_propagation/chapter_overview.html[Delta Propagation].
While _race conditions_ between competing HTTP requests (accessing the same HTTP Session) cannot be completely avoided with
any session provider, sending only the delta (or changes) minimizes the chance of _lost updates_, especially in a highly clustered
Web environment. By using PDX Serialization, your HTTP Session state is immediately transferable across environments, from non-managed,
standalone environments to managed environments, like https://pivotal.io/platform[Pivotal Cloud Foundry (PCF)]
using https://pivotal.io/platform/services-marketplace/data-management/pivotal-cloud-cache[Pivotal Cloud Cache (PCC)].

* Custom `Change Detection` - while most session implementations consider the session to be dirty anytime anything is written
to the session, even when your application domain objects stored in the session have not changed, SSDG will intelligently
determine whether there is anything to send before writing it to the wire.  OOTB, SSDG will look at any application domain objects
that implement Apache Geode's https://geode.apache.org/releases/latest/javadoc/org/apache/geode/Delta.html[Delta] interface
and use that to determine if your application domain objects are indeed dirty before sending the delta. If your objects do not
implement the `Delta` interface, or the object is not the same, then it functions like all other Spring Session providers.
If you prefer, you may specify your own rules composed with the `IsDirtyPredicate` strategy interface.

* Powerful `Pub/Sub` - Apache Geode and Pivotal GemFire both provide a very powerful and robust client/server
https://geode.apache.org/docs/guide/{geode-version}/developing/events/chapter_overview.html[event distribution and handling sub-system]
leveraged by SSDG in order to reliably manage session state, especially in a distributed/clustered environment.

These and many more Apache Geode or Pivotal GemFire features may be leveraged in your application environment to
achieve resilient, highly available (HA), durable, consistent, and even multi-clustered (WAN), persistent
session statement management.

The best part, SSDG allows you to use either Apache Geode or Pivotal GemFire interchangeably without having to change
a single line of code.  Simply change your dependency from `org.springframework.session:spring-session-data-geode`
to `org.springframework.session:spring-session-data-gemfire`, or vice versa, and you can seemlessly move between
either Apache Geode or Pivotal GemFire, or even PCC.

No other Spring Session provider offers you the same type of flexibility and power in 1 solution, especially as
your requirements and UC change (e.g. from simple session caching to a full on _System of Record_ with
_distributed compute_ and _streaming capabilities_).

== Code of Conduct

This project adheres to the Contributor Covenant link:CODE_OF_CONDUCT.adoc[code of conduct].
By participating, you  are expected to uphold this code. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io.

== Documentation

Documentation for _Spring Session for Apache Geode and Pivotal GemFire_ can be found
https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/{version}/reference/html5/[here]
and Javadoc is available https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/{version}/api/[here].

= Spring Session Project Site

You can find the documentation, issue management, support, samples, and guides for using _Spring Session_
at https://projects.spring.io/spring-session/

= License

_Spring Session_ is Open Source Software released under the https://www.apache.org/licenses/LICENSE-2.0.html[Apache 2.0 license].
