JMC-6513: Wrong version of compiled classes when importing JMC maven projects in Eclipse with JDT Default Compiler Level of 11

[Marcus Hirt]

Hi Christoph,

I agree; I see no harm in taking this patch, though I would love to
see Maven and Eclipse collaborate better. In the best of all worlds,
no Eclipse project files would be required, Maven would be the one
source of truth and a simple Maven import would be all that is
required. Guru, do you have any strong opinion here?

Kind regards,
Marcus

On Fri, Jun 28, 2019 at 9:58 PM Langer, Christoph
<christoph.langer at sap.com> wrote:
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> Ping: Any comments for this?
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>
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> From: Langer, Christoph
> Sent: Donnerstag, 20. Juni 2019 23:56
> To: jmc-dev at openjdk.java.net
> Subject: JMC-6513: Wrong version of compiled classes when importing JMC maven projects in Eclipse with JDT Default Compiler Level of 11
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>
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> Hi,
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> please let me know what you think of this patch:
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> Bug: https://bugs.openjdk.java.net/browse/JMC-6513
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> Webrev: http://cr.openjdk.java.net/~clanger/webrevs/JMC-6513.0/
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> I'm having issues when importing the jmc projects into my Eclipse which has a default JDK compiler level of 11. Although the JMC projects define a JSE18 in their .classpath files, the classes get compiled with Java 11 version. This can be helped by creating ".settings/org.eclipse.jdt.core.prefs" files which set the compiler to 1.8. Then these issues were gone. So, in my patch I propose to add them. A Java compiler level of 8 is needed in Eclipse because I want to be able to run/debug with any JDK down to 8.
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> Something is a bit weird though with maven import. On my Windows Eclipse I observe that the import would generate these .settings/org.eclipse.jdt.core.prefs as contained in the patch. However, this import also regenerates some .classpath files which brings other issues and is not what is wanted. On my Eclipse on Mac, I don't see neither .settings/org.eclipse.jdt.core.prefs getting generated nor .classpath files rewritten. Maven settings in both Eclipse installations seem to be the same. Does anybody have an explanation for that?
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> So, AFAICS, I don't think my patch causes any harm and can safely be used. There's also precedence for that such as the projects in jmc/core (which compile with JDK 1.7), as well as project jmc/application/org.openjdk.jmc.osgi.extension which was introduced by the patch for JMC-5859 [1].
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> Thanks
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> Christoph
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> [1] http://hg.openjdk.java.net/jmc/jmc/rev/2cc768144a86
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