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= Spring Session for Apache Geode & Pivotal GemFire

_Spring Session_ core provides an API along with several provider implementations to manage user sessions
and simplify 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 these core _Spring Session_ features, _Spring Session for Apache Geode_ (SSDG) positions either
http://geode.apache.org/[Apache Geode] or https://pivotal.io/pivotal-gemfire[Pivotal GemFire]
as a session repository provider along with additional capabilities required by enterprise class solutions:

* Custom `Expiration Policies` - in addition to the default 30 minute session _idle expiration timeout_ (TTI),
SSDG also supports _fixed duration expiration timeout_ (e.g. expire the session after 1 hour regardless of
whether the session is active or inactive).  User may also define custom expiration policies using the
https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/2.1.1.RELEASE/api/org/springframework/session/data/gemfire/expiration/SessionExpirationPolicy.html[`SessionExpirationPolicy`] interface.
See https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/2.1.1.RELEASE/reference/html5/#httpsession-gemfire-expiration[documentation] for more details.

* Custom `Serialization` - in addition to the default Apache Geode https://geode.apache.org/docs/guide/18/developing/data_serialization/gemfire_pdx_serialization.html[PDX Serialization] format,
users may configure Apache Geode https://geode.apache.org/docs/guide/18/developing/data_serialization/gemfire_data_serialization.html[Data Serialization]
with full support for https://geode.apache.org/docs/guide/18/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 chances of lost update, especially in a highly clustered
Web environment. By using PDX Serialization, your HTTP Session state is immediately transferable across environments, from non-managed,
standalone 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 may not have 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/18/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 and consistent, even multi-clustered (WAN) and 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, and even PCC.

No other Spring Session provider offers you this sort of flexibility and power in 1 solution, especially as your
requirements change and needs grow (e.g. from simple caching to a full on _System of Record_ with distribute compute
and stream 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/2.1.1.RELEASE/reference/html5/[here]
and Javadoc is available https://docs.spring.io/autorepo/docs/spring-session-data-geode-build/2.1.1.RELEASE/api/[here].

= Spring Session Project Site

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

= License

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