[[WildFly_and_WildFly_Preview]]
= WildFly and WildFly Preview
WildFly team;
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(C) 2021 The original authors.

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= Different flavors of WildFly

Beginning with the WildFly 22 release, the WildFly project began producing two variants of
its landmark application server -- the standard "WildFly" variant and the new "WildFly Preview".

The standard "WildFly" variant is the classic server that users have been familiar with for many
years now. It's a very mature server, with a lot of care taken to ensure new features are fully
realized and to limit the number of incompatible changes between releases.

WildFly Preview is a tech preview variant of the server. The goal of WildFly Preview is to give
the WildFly community a look at changes that are likely to appear in future releases of the standard
WildFly server. The aim is to get feedback on in-progress work, so it is more likely that features
will not be fully realized, and a greater number of incompatible changes may appear from release
to release. The amount of testing WildFly Preview undergoes will generally not be as high as the
standard WildFly variant.

The expectation is on any given release date, both standard WildFly and WildFly Preview will be released.

[WARNING]
====

A WildFly Preview release will have the same version number and suffix (Beta, Final, etc) as the
main WildFly release, but regardless of the suffix, a WildFly Preview release should be treated
as a Technical Preview release.
====

== Getting WildFly Preview

The zip or tar.gz file for WildFly Preview is available at link:https://wildfly.org/downloads[https://wildfly.org/downloads]
right next to the main WildFly release files for the same version.

For bootable jar users and Galleon CLI users, we provide a Galleon feature pack for WildFly Preview. The
Galleon feature pack location for the feature pack is ``wildfly-preview@maven(org.jboss.universe:community-universe)`` and the Maven coordinate is ``org.wildlfly:wildfly-preview-feature-pack``.
This feature pack is the WildFly Preview analogue to main WildFly's ``wildfly@maven(org.jboss.universe:community-universe)`` (Maven coordinate ``org.wildfly:wildfly-galleon-pack``).

== WildFly Preview and Jakarta EE

Often, but not always, a key difference between standard WildFly and WildFly Preview is support for different versions of Jakarta EE. The WildFly project uses WildFly Preview to showcase full or partial support for new versions of Jakarta EE, including releases like EE 11 that are not yet released for general availability.

Note that formally certifying WildFly Preview as compatible implementation of Jakarta EE is not a priority
for the WildFly project and may not happen at the time of a release, or ever. Users interested in formal EE
compliance of WildFly Preview should check the https://github.com/wildfly/certifications/tree/EE10[WildFly Certifications repository].

[wildfly-preview-ee11]
=== EE 11 Support in WildFly Preview

The 32 release introduces a significant inflection in how we are using WildFly Preview. Beginning with this release we are starting to use WildFly Preview to provide a look at what we're doing for Jakarta EE 11 support.  EE 11 is not yet GA, and standard WildFly won't support EE 11 before the WildFly 34 release, at earliest. But there are milestone, release candidate and final releases of many EE 11 specs and implementations available, so we decided to provide those in WildFly Preview. This means for a number of EE APIs, WildFly Preview no long provides an EE 10 compatible implementation.

However, for a number of specifications that are planning changes for EE 11 we are still offering the EE 10 variant. In future releases we'll shift those to the EE 11 variants.

The following table lists the various Jakarta technologies offered by WildFly Preview 32, along with information about which EE platform version the specification relates to. Note that a number of Jakarta specifications are unchanged between EE 10 and EE 11, while other EE technologies that WildFly offers are not part of EE 11.

[cols=",,",options="header"]
|=======================================================================
|Jakarta EE Technology |Specification Version| EE Version

|Jakarta Activation| 2.1 |10 & 11

|Jakarta Annotations| 3.0.0 |11

|Jakarta Authentication| 3.0 |10

|Jakarta Authorization| 3.0.0-M2 |11

|Jakarta Batch| 2.1 |10 & 11

|Jakarta Concurrency| 3.1.0-M1 |11

|Jakarta Connectors| 2.1 |10 & 11

|Jakarta Contexts and Dependency Injection| 4.1.0 |11

|Jakarta Debugging Support for Other Languages| 2.0 |10 & 11

|Jakarta Dependency Injection| 2.0 |10 & 11

|Jakarta Enterprise Beans| 4.0 |10 & 11

|Jakarta Enterprise Web Services| 2.0 |10 xref:note1[^1^]

|Jakarta Expression Language| 6.0.0 |11

|Jakarta Faces| 4.1.0-M1 |11

|Jakarta Interceptors| 2.2.0 |11

|Jakarta JSON Binding| 3.0 |10 & 11

|Jakarta JSON Processing| 2.1 |10 & 11

|Jakarta Mail| 2.1 |10 & 11

|Jakarta Messaging| 3.1 |10 & 11

| Jakarta MVC
(_preview stability only_)| 2.1| N/A xref:note2[^2^]

|Jakarta Persistence| 3.2.0-M2 |11

|Jakarta RESTful Web Services| 3.1 |10

|Jakarta Security| 4.0.0-M2 |11

|Jakarta Server Pages| 3.1 |10

|Jakarta Servlet| 6.1.0-M2 |11

|Jakarta SOAP with Attachments| 1.3 |10 xref:note1[^1^]

|Jakarta Standard Tag Library| 3.0 |10 & 11

|Jakarta Transactions| 2.0 |10 & 11

|Jakarta Validation| 3.1.0-M2 |11

|Jakarta WebSocket| 2.2.0-M1 |11

|Jakarta XML Binding| 4.0 |10 xref:note1[^1^]

|Jakarta XML Web Services| 4.0 |10 xref:note1[^1^]
|=======================================================================

Notes:

. [[note1]]This Jakarta EE 10 technology is not part of EE 11 but is still provided by WildFly Preview.
. [[note2]]Jakarta MVC is an independent specification that is not part of the Jakarta EE Platform or the Web or Core Profile.


=== WildFly Preview Support for EE 8 Deployments

The APIs that WildFly Preview exposes to deployments are the EE 10 or 11 APIs, so all the classes and interfaces are in the
jakarta.* packages. But you _may_ be able to run an existing EE 8 application on WildFly Preview.

What we've done is we've added to the server's handling of _managed_ deployments a bytecode and text file transformation
process to convert EE 8 content into EE 9.  It bytecode transforms deployment jars to alter
references to EE 8 packages in the class file constant tables to change from javax.* to jakarta.*. The transformation
goes beyond simple package renames; a number of other known differences between EE 8 and EE 9 are handled. We owe a
great deal of thanks to the community behind the link:https://projects.eclipse.org/projects/technology.transformer[Eclipse Transformer]
project for their work on the underlying transformation tool.

As noted above, this handling is only applied to _managed_ deployments. A managed deployment is one where a management
client (the CLI, HAL console or the deployment scanner) presents deployment content to the server and the server makes
a copy of it in its internal deployment content repository. The content that gets installed into the runtime is that internal copy.
Unmanaged deployments that use EE 8 APIs will not work. We transform managed deployments when we copy the deployment
content into the internal content repo. For unmanaged deployments we use the original content file(s) the user provides,
and WildFly Preview won't modify those files as we don't regard them as being 'owned' by the server.

Note that the deployment transformation feature will not update the deployment to adapt to any API differences between
Jakarta EE 9 and EE 10 or later. It only covers the javax to jakarta name changes that came with EE 9.

In the long run it's better for users if they either convert their application source to EE 10 APIs, or use build-time
tooling that we expect the Jakarta ecosystem to provide over time to do transformation at build time.  But some
applications just can't be changed, so the server-side solution WildFly Preview provides can handle those cases.

This deployment transformation feature will be removed from WildFly Preview in a future release. However, it is likely
that the WildFly developers will offer a separate Galleon feature pack that can be used to add this behavior into both
standard WildFly and WildFly Preview.

== WildFly Preview and Java SE 11

Standard WildFly supports Java SE 11, 17 and 21, but, as a result of this shift to EE 11 APIs, *WildFly Preview no longer supports running on Java SE 11.* Going forward, if you want to use WildFly Preview you'll need to use SE 17 or higher.  A number of EE 11 APIs no longer produce SE 11 compatible binaries, which means an EE 11 runtime can no longer support SE 11.

[NOTE]
====
This removal of support for SE 11 has no impact on standard WildFly. Standard WildFly 32 continues to support running on SE 11. We do, however, encourage users to move to SE 17 or later, as the general Java ecosystem is moving away from SE 11 support, and eventually standard WildFly will as well.
====

== Other Differences in WildFly Preview

WildFly Preview is intended to help get community exposure for other changes we plan to
make in the server. Here are the key differences between standard WildFly and WildFly Preview:

* WildFly Preview is not a Jakarta EE 10 compatible implementation. It also is not a MicroProfile platform compatible
implementation. Most EE 10 and MicroProfile applications are expected to run well on WildFly Preview, but it is not
certified compatible.
* The standard configuration files do not configure an embedded messaging broker. Instead, they configure the
link:Admin_Guide{outfilesuffix}#Messaging[`messaging-activemq` subsystem] to provide connections to a remote ActiveMQ Artemis broker. (It's a task for the user to
run such a broker or to update the config to integrate with a different broker.) We want WildFly out-of-the-box to be
more of a cloud native appserver and having an embedded messaging broker in the default configuration is not cloud native.
A WildFly container in the cloud running an embedded broker is not scalable, as multiple broker instances need separate
configuration to act as a primary or backup. An embedded messaging broker also has more advanced persistent storage
requirements than a server primarily dedicated to handling HTTP requests would have. Note however that running an
embedded broker is still supported. We've added to the $WILDFLY_HOME/docs/examples/configs folder an example
``standalone-activemq-embedded.xml`` configuration showing its use.
* The Hibernate ORM integration used by the link:Developer_Guide{outfilesuffix}#JPA_Reference_Guide[JPA subsystem's] Hibernate Search feature supports using outbox polling as coordination strategy for automatic indexing.