8256362: JavaFX must warn when the javafx.* modules are loaded from the classpath

[kevinrushforth]

This fix adds documentation and a warning to clarify that loading the JavaFX modules from the classpath is not a supported configuration. This will not affect deployments that put the JavaFX modular jars on the classpath, but will simply warn that it is an unsupported mode.

JavaFX is built and distributed as a set of named modules, each in its own modular jar file. This supports running both modular and non-modular applications.

The JavaFX runtime expects its classes to be loaded from a set of named javafx.* modules, and does not support loading those modules from the classpath. The Java launcher will fail to load applications that extend javafx.application.Application unless the javafx.graphics module is on the module path.

Applications that do not extend javafx.application.Application can be loaded even if the javafx.* classes are loaded from the classpath, but this is an unsupported configuration.

This creates the perception that there is a problem with the standard case of loading a subclass of javafx.application.Application, since it fails to load in the case where the JavaFX classes are loaded from the classpath. Further, allowing applications to run in an unsupported mode that likely has bugs creates a maintenance burden. Another problem is that when the JavaFX classes are loaded from the classpath, it breaks encapsulation, since we mo longer get the benefit of the java module system.

The primary reason given for application deployments loading the javafx modules on the classpath usually boils down to one of tooling support, although both gradle and maven now support modules as do all of the popular IDEs.

/csr needed
/reviewers 2

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8256362: JavaFX must warn when the javafx.* modules are loaded from the classpath

Reviewers

• Ambarish Rapte (@arapte - Reviewer)
• Pankaj Bansal (@pankaj-bansal - Committer)
• Johan Vos (@johanvos - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jfx pull/354/head:pull/354
$ git checkout pull/354

[bridgekeeper]

👋 Welcome back kcr! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@kevinrushforth this pull request will not be integrated until the CSR request JDK-8256422 for issue JDK-8256362 has been approved.

[openjdk]

@kevinrushforth
The number of required reviews for this PR is now set to 2 (with at least 1 of role reviewers).

[mlbridge]

Webrevs

• 00: Full (0a9716f)

[arapte]

Looks good to me.

[kevinrushforth]

I am switching the target branch to jfx16 now that we are in RDP1 and have forked the stabilization branch.

[openjdk]

@kevinrushforth This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8256362: JavaFX must warn when the javafx.* modules are loaded from the classpath

Reviewed-by: arapte, pbansal, jvos

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 24 new commits pushed to the jfx16 branch:

• 9dd2058: 8259639: GitHub actions: build fails on Linux due to missing apt-get update
• 9c84c77: 8211294: ScrollPane content is blurry with 125% scaling
• c197b62: 8242621: TabPane: Memory leak when switching skin
• e74f679: 8254101: Update copyright header for files modified in 2020
• 53fe38b: 8258592: Control labels in Dialogs are truncated at certain DPI scaling levels
• e61b923: 8242361: JavaFX Web View crashes with Segmentation Fault, when HTML contains Data-URIs
• fb8e0cd: 8253356: JavaFX Terminology Refresh
• f2928d9: 8256983: GitHub actions: specify the version of each platform OS and compiler
• ebb59e9: 8201568: zForce touchscreen input device fails when closed and immediately reopened
• 97d655f: 8256012: Fix build of Monocle for Linux
• ... and 14 more: https://git.openjdk.java.net/jfx/compare/dd22cd2d97d4bfc305e44f2e77b4c104c62ff31f...jfx16

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the jfx16 branch, type /integrate in a new comment.

[johanvos]

This looks good, and I didn't hear objections (on the warning) on this PR nor in JBS or the mailinglist, so this is ok to be merged.

[kevinrushforth]

/integrate

[openjdk]

@kevinrushforth Since your change was applied there have been 24 commits pushed to the jfx16 branch:

• 9dd2058: 8259639: GitHub actions: build fails on Linux due to missing apt-get update
• 9c84c77: 8211294: ScrollPane content is blurry with 125% scaling
• c197b62: 8242621: TabPane: Memory leak when switching skin
• e74f679: 8254101: Update copyright header for files modified in 2020
• 53fe38b: 8258592: Control labels in Dialogs are truncated at certain DPI scaling levels
• e61b923: 8242361: JavaFX Web View crashes with Segmentation Fault, when HTML contains Data-URIs
• fb8e0cd: 8253356: JavaFX Terminology Refresh
• f2928d9: 8256983: GitHub actions: specify the version of each platform OS and compiler
• ebb59e9: 8201568: zForce touchscreen input device fails when closed and immediately reopened
• 97d655f: 8256012: Fix build of Monocle for Linux
• ... and 14 more: https://git.openjdk.java.net/jfx/compare/dd22cd2d97d4bfc305e44f2e77b4c104c62ff31f...jfx16

Your commit was automatically rebased without conflicts.

Pushed as commit 1d45997.

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