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Re: [cross-project-issues-dev] Will Your Project Work When Running on Java 9?


JDT is working on a branch specifically for Java 9 support as documented here:

The results are published in the platform's so-called Y builds.  The results are not on the Oxygen train and are not currently targeting to be released with Oxygen.0.   So no, M6 will not include anything for Java 9 support and no you cannot specify a Java 9 SDK in the "Installed JREs" preferences page with M6 (nor with Oxygen.0).  

Furthermore, as described in the Wiki and in Wayne's blog, the IDE itself will not run on a Java 9 VM, unless you specify the right magical VM argument.  And even when you do, everything might not function because few of us have tested this.  One part of Oomph was very broken and it appears MPC is also somewhat broken.  Most other things appear to be okay, but that's why I would strongly encourage each team to test their own project functionality, and to help test JDT's Java 9 support (at least in terms of compatibility for current development which doesn't actually exploit Java 9 features) while they're at it because that will help ensure that when Java 9 itself releases, Eclipse work well with it, and when Oxygen.1 releases, JDT's Java 9 support will work well too (at least in terms of compatibility).

I believe JDT does not need to run on a Java 9 VM in order to support Java 9 development, but Dani can best explain that when he provides additional details later in the week.

On 08.03.2017 12:08, Ed Willink wrote:


I'm confused. What are the JDT Java 9 builds?

Will M6 include everything necessary for explicit use of a Java 9 SDK in a compatibility mode where existing projects are not using any Java 9 features? i.e specifying Java 9 as my JAVA_HOME, and Java 9 as my installed preference within Eclipse.


Ed Willink

On 08/03/2017 10:18, Ed Merks wrote:


Yes, though you definitely need that if you want to use Window -> Preferences -> Java -> Installed JREs to be able to point to a Java 9 JDK; as you know that just doesn't work without JDT's Java 9 support because it won't be recognized as a JDK/JRE otherwise.  And of course project testers definitely want that if they want to be able to debug-launch their self-hosted project code with a Java 9 JDK to debug anything that might be going wrong.  And in all cases it seems good (to me) if everyone tests JDT's Java 9 support while they're testing that Java 9 works also for their running code in the installation.

On 08.03.2017 10:30, Daniel Megert wrote:
Thanks Ed.

I will follow up on this with additional details later this week.

One important thing: you do not need JDT's Java 9 builds in order to run Eclipse with Java 9. This is only necessary if you want to test new Java 9 related functionality.


From:        Ed Merks <ed.merks@xxxxxxxxx>
To:        Cross project issues <cross-project-issues-dev@xxxxxxxxxxx>
Date:        08.03.2017 10:05
Subject:        [cross-project-issues-dev] Will Your Project Work When Running on        Java 9?
Sent by:        cross-project-issues-dev-bounces@xxxxxxxxxxx


Wayne recently blogged about Eclipse's Java 9 support:

Also, the planning council has been discussing the Oxygen release schedule with respect to Java 9 support:

Most projects are likely not doing anything specific to support the new feature of Java 9 so probably most of you aren't so concerned about what you need to do.  But it's likely that users will install Java 9 once it's released (in July) and that makes it likely users will try to run Eclipse itself with a Java 9 VM.  So the question is, will your project work when running on Java 9?  Probably, but maybe not.  I would strongly encourage you to test that!

Wayne's blog describes what you need to do.  To make testing even easier, I've automated the setup process with an Oomph Configuration.  What's a configuration you ask?

I've attached a configuration that does several things. 

  • The installation portion of the configuration
    • adds a p2 task to reference the platform's Y build update site, i.e., the builds that contain JDT's early access Java 9 support (so whatever product you install, it will consider installing it from the Y build),
    • and adds the --add-modules VM argument to the eclipse.ini (so launching will actually function).
  • The workspace portion of the configuration
    • redirects the 4.7 I builds URL to the 4.7 Y builds URL, so if you using Oomph's targlets to provision your target platform, and provision an Oxygen target platform, it will provision one that uses the 4.7 Y builds, so you can debug launch your project code with a Java 9 IDE,
    •  and creates a JDT "Installed JRE" that references a Java 9 JDK, and that includes the --add-modules VM argument so you can launch a self hosting IDE running on Java 9.
You can try the configuration out with the latest installer.  Either update the one you have (from the menu in Simple mode or the toolbar button at the bottom in advanced mode) or download the latest one from:

To apply the configuration, you can drag and drop the email attachment to the title area of the installer (both in simple mode and advanced mode).  Alternatively you can save the configuration attachment and copy the file itself (or the contents of the file), to the clipboard, and then apply it (via the menu in simple mode or via the first toolbar button next to the search field in advanced mode).  If you're in simple model, applying the configuration will notice it has a workspace portion and will offer to switch to advanced mode, or will offer just apply the installation portion of the configuration.  You can do either.  Now you can proceed to choose a product (and optionally a project) to provision.

If you're using Java 9 for the first time, and you've only unzipped it so far, you'll need to make Oomph aware that your Java 9 JDK is available on your machine. 
  • In simple mode you can do this as follows.  Choose whatever product you want to install on the first page.   On the second page, choose the "Oxygen" version of that product.   For the Java VM choice, use the folder button to open the Java Virtual Machines dialog and use the Browse button to locate the Java 9 JDK on your file system.   Once it's displayed, make sure it's selected and hit OK.  This will create an Oxygen installation of whatever product you've chosen, configured to use a Java 9 VM along with the right VM arguments so it can actually launch successfully.
  • In advanced model you can do this as follows.   Choose whatever product you want to install on the first page and choose the Oxygen Product Version.  Use the folder button next to the Java VM choice and use the Browse button to locate the Java 9 JDK on your file system.  Make sure it's selected in the combo box.  Advance to the next page (Project page).  Here you can choose your Project setup.  If you don't have one, I'll bet your project doesn't have a lot of external contributors and I'll bet that you spend a lot of time on manually setting up your workspace.   I typically choose the Oomph project (or EMF project) on the Project page, and then I advance to the Variables page to select the Oxygen target platform for testing against the latest platform code.
Whatever steps you take, the result will be to launch an Oxygen product based on the platform's Oxygen Y build, complete with Java 9 early access support and running on Java 9 early access JVM.  If you choose a project as well, the workspace will be populated with all your source code using an Oxygen target platform also with Java 9 support and will be compiled against a Java 9 JDK.  So you can launch and debug, without changing your project setup at all.

Probably your project will work just fine, but don't count on it!  For example, Oomph uses a class derived from java.util.Properties in order to save properties files.  The implementation of that class is changed slightly in Java 9, with the net effect that any properties file we save ends up being empty, no stack traces or other visible symptoms of the failure point.  The overall effect was that any attempt to install/update anything in the IDE (or to produce an installation with the installer application) resulted in an empty config.ini.  As you can imagine, a corrupted config.ini prevents the installation from running.  So it was a pretty catastrophic failure!  Thank goodness it's already fixed, even for the next Neon release.

During testing I also see this stack trace in my Error log:

java.lang.reflect.InaccessibleObjectException: Unable to make field private static volatile accessible: module java.base does not "opens" to unnamed module @26749efe
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(
    at java.base/java.lang.reflect.Field.checkCanSetAccessible(
    at java.base/java.lang.reflect.Field.setAccessible(
    at org.eclipse.epp.internal.mpc.core.util.ProxyHelper.getDefaultAuthenticator(
    at org.eclipse.epp.internal.mpc.core.util.ProxyAuthenticator.uninstall(
    at org.eclipse.epp.internal.mpc.core.util.ProxyHelper.uninstallAuthenticator(
    at org.eclipse.epp.internal.mpc.core.util.ProxyHelper.releaseProxyService(
    at org.eclipse.epp.internal.mpc.core.MarketplaceClientCorePlugin.stop(
    at org.eclipse.osgi.internal.framework.BundleContextImpl$
    at org.eclipse.osgi.internal.framework.BundleContextImpl$
    at java.base/ Method)
    at org.eclipse.osgi.internal.framework.BundleContextImpl.stop(
    at org.eclipse.osgi.internal.framework.EquinoxBundle.stopWorker0(
    at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.stopWorker(
    at org.eclipse.osgi.container.Module.doStop(
    at org.eclipse.osgi.container.Module.stop(
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.decStartLevel(
    at org.eclipse.osgi.container.ModuleContainer$ContainerStartLevel.doContainerStartLevel(
    at org.eclipse.osgi.container.SystemModule.stopWorker(
    at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule.stopWorker(
    at org.eclipse.osgi.container.Module.doStop(
    at org.eclipse.osgi.container.Module.stop(
    at org.eclipse.osgi.container.SystemModule.stop(
    at org.eclipse.osgi.internal.framework.EquinoxBundle$SystemBundle$EquinoxSystemModule$
    at java.base/

I'm not sure what to make of that, but it suggests that MPC might well not function when running on Java 9.

So in the end, I think there isn't so much to worry about, but nevertheless, I strongly encourage each team to test their project's readiness so we can all avoid hassles and embarrassment when Java 9 is finally released.  I've tried to help make that as easy as possible...

Ed[attachment "OxygenJava9EarlyAccessBetaConfiguration.setup" deleted by Daniel Megert/Zurich/IBM]
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