feat(osgi): add org.osgi.framework.executionenvironment

[gnunzi]

This PR adds org.osgi.framework.executionenvironment=JavaSE-9 to the config.ini, so that Equinox ClassLoaders do not load JRE-classes again. This avoids LinkageError for javax.* classes.

Equinox reads the lists "jvm packages" from the property org.osgi.framework.bootdelegation and "delegates" these packages to the jvm class loader.

Without "bootdelegation" an Equinox ClassLoader loads the javax.* classes and a LinkageError occurs. See related issues below.

Related Issue:
This PR fixes #5630 and #4141.

Description of the solution adopted:
The javax.* classes must not be loaded by Equinox, since they are provided by the jre and loaded by the jvm itself (boot classloader / platform classloader).

The solution is to specify org.osgi.framework.executionenvironment. This is based on the following thread:

So as long as you define a "org.osgi.framework.executionenvironment", equinox should load the right JVM packages and export them for consumption by the bundles.

From my understanding the setting org.osgi.framework.executionenvironment tells Equinox to load the JSE-9 profile which in turn contains the properties org.osgi.framework.system.packages and org.osgi.framework.bootdelegation (see here and here)

The mechanism of Class Loading is explained in https://docs.osgi.org/specification/osgi.core/8.0.0/framework.module.html#framework.module.parentdelegation.

org.osgi.framework.executionenvironment is explained here: https://docs.osgi.org/specification/osgi.core/7.0.0/framework.lifecycle.html

Nore that org.osgi.framework.executionenvironment is deprecated in older OSGi releases, but valid in R4 like Equinox.

Screenshots:

N/A

Manual Tests

Any side note on the changes made:

StackTrace in Java 1.8:
Caused by: java.util.concurrent.ExecutionException: java.lang.LinkageError: loader constraint violation in interface itable initialization: when resolving method "org.h2.jdbcx.JdbcXAConnection.getXAResource()Ljavax/transaction/xa/XAResource;" the class loader (instance of org/eclipse/osgi/internal/loader/EquinoxClassLoader) of the current class, org/h2/jdbcx/JdbcXAConnection, and the class loader (instance of <bootloader>) for interface javax/sql/XAConnection have different Class objects for the type javax/transaction/xa/XAResource used in the signature

Especially look at the following: the class loader (instance of org/eclipse/osgi/internal/loader/EquinoxClassLoader) of the current class, org/h2/jdbcx/JdbcXAConnection, and the class loader (instance of <bootloader>) [...] have different Class objects for the type javax/transaction/xa/XAResource used in the signature.

[github-actions]

This pull request is stale because it has been open for 60 days with no activity.

[MMaiero]

@gnunzi This PR has been flag by the automation as stale. Are you still willing to contribute this change? Or can this be closed?

[gnunzi]

@MMaiero In principle yes. I believe this PR is the solution to java.lang.LinkageError that has been reported a couple of times.
To my understanding the LinkageError occurs when a bundle is loaded after the start, e.g. hot-deployment in a Docker container (my observation) or plugin-deployment throught the UI (reported in #5630 and #4141).

On the other side, it is difficult for me to reproduce this error and check the result. I would keep this PR with the hope to reproduce the error.

In any case we are using org.osgi.framework.executionenvironment=JavaSE-9 with no side-effect already. I could submit the PR right away if the text on top is convincing enough. For a reproducable error I need more time.