Accessibility provider classpath

[Vladimir Petko]

Hi,

A recap of the problem i am trying to solve below:

Java accessibility requires accessibility provider classes to be
present in the application classpath.

In Java 8 accessibility provider jar was added to the "lib/ext"
directory and the accessibility provider was added to the boot
classpath. Some Linux distributions carried a patch that modified the
boot classpath for Java 11 and up to include a predefined
accessibility provider.

Updating the boot classpath was a security risk and did not allow for
alternative implementations of the accessibility provider that are
configurable system-wide.

Since Java runtime attempts to load accessibility using the
application's classpath, a user has to modify each application's
classpath to enable accessibility. This is a bad user experience.
Sometimes it is not possible, e.g. the application files are
immutable.

Accessibility provider classpath can be specified in a new additional
property in accessibility.properties. The older versions of JDK will
ignore it and the change will not break an existing functionality.

I have prepared a prototype[1] and was wondering if it would be ok to
raise an enhancement issue and implement it.

Best Regards,
 Vladimir.

[1] https://github.com/openjdk/jdk/compare/master...vpa1977:jdk:accessibility_proto

On Thu, Sep 21, 2023 at 10:21 AM Samuel Thibault
<samuel.thibault at ens-lyon.org> wrote:
>
> Vladimir Petko, le jeu. 21 sept. 2023 10:11:38 +1200, a ecrit:
> > Samuel, please correct me if I'm wrong. The requirement is for the
> > per-user (or system-wide) enablement of accessibility. The
> > per-application setup is a bad user experience, and it would be nice
> > to have a single point - properties file - that enables it.
>
> Yes, that's it.
>
> It is meaningless to enable accessibility only for some applicatins:
> either the user needs it for all applications, or they don't need it at
> all.
>
> Samuel
>
> > Java 8 achieves this by putting the accessibility provider jar in the
> > 'ext' directory. Java 11 and up requires including an accessibility
> > provider in the modules files.
> >
> > Any updates and fixes to the accessibility provider will require new
> > releases of the openjdk package in Debian and Ubuntu. Adding
> > accessibility providers to the build dependencies of the openjdk
> > package also creates a circular build dependency that might introduce
> > issues requiring careful synchronization between releases.
> >
> > I propose to add a new property 'java.accessibility.module_path'. The
> > property will contain the list of locations of accessibility modules.
> > Toolkit will construct the classloader using this path and the system
> > class loader as a parent. Older releases will ignore this property.
> >
> > This feature will allow installation of the accessibility provider
> > separate from the openjdk package and will satisfy the requirement of
> > per-user and system-wide enablement of the accessibility provider.
> >
> > Best Regards,
> >  Vladimir.
> >
> > On Thu, Sep 21, 2023 at 9:48 AM Philip Race <philip.race at oracle.com> wrote:
> > >
> > > Can you explain your need for this (a lot) better ?
> > >
> > > The location and loading is specified to be done by
> > > java.util.ServiceLoader.
> > > Whilst this might be possible by some enhanced syntax, which if present
> > > invokes ServiceLoader specifying a ClassLoader for this jar file, it
> > > would clearly be new API and only for future releases.
> > > NB it would also be fiddly to implement as the value of the property is
> > > a list of class names and
> > > you can't add jar names to that without breaking older JDKs and
> > > so you'd need some way to match new lines referencing the JAR file for
> > > each class ..
> > >
> > > And likely we'd want to have new APIs like this - if they make sense - to
> > > be focused on a module, not a jar, but building a runtime image from
> > > modules using jlink is a normal thing to do, so I'm not sure what such
> > > an API would look like and seems to be not what you want.
> > >
> > > I also don't understand  the use case / problem.
> > > Whatever launches your application can set
> > > -Djavax.accessibility.assistive_technologies=<..>
> > > and  set the -cp to include your jar and you don't need to do anything
> > > to the runtime image.
> > >
> > > -phil
> > >
> > > On 9/20/23 1:33 PM, Vladimir Petko wrote:
> > > > Hi,
> > > >
> > > > Java accessibility.properties (.accessibility.properties) allows
> > > > setting the class name of the accessibility provider but not the jar
> > > > file containing it.
> > > >
> > > > Was there any consideration that prevents this feature from being
> > > > implemented, such as security?
> > > >
> > > > It would be nice to have it implemented to allow system-wide/per-user
> > > > configuration of the accessibility provider without rebuilding the
> > > > runtime image.
> > > >
> > > > If this is something acceptable, I am happy to create an enhancement
> > > > issue and work on it.
> > > >
> > > > Best Regards,
> > > >   Vladimir.
> > >
> >
>
> --
> Samuel
> ---
> Pour une évaluation indépendante, transparente et rigoureuse !
> Je soutiens la Commission d'Évaluation de l'Inria.