Cannot load project due to tools.jar

[demlik]

Hi, I am trying to import a project which for one reason or another has a system dependency to JDK tools.jar.

All versions of Eclipse which now require Java11+ seem to have issue resolving this dependency even when JDK8 is added to installed JRE section with tools.jar added as an external dependency.

Reverting to a version of Eclipse which can be run under JDK8 (via -vm) works perfectly fine.

Maybe m2e is using the internal JREs home directory instead of the specified JREs home directory…

Is there a way to resolve this issue?

[glhez]

I have a similar issue : trying to reference tools.jar using these as reference: https://stackoverflow.com/questions/3080437/jdk-tools-jar-as-maven-dependency

The problem is that to reference the tools.jar, you would often needs to do ${java.home}/../lib/tools.jar which is a path only working in Java <=8.

Since Eclipse and Lemminx is running Java 17, the ${java.home} will resolve to that JDK.

Not sure what can be done, but in Eclipse, you can add tools.jar in the JRE.
And perhaps use profile machinery for Maven builds: https://github.com/olivergondza/maven-jdk-tools-wrapper

Note that if you were to use toolchains to build in Java 8 with Maven running with Java 17, you would have the same problem.

Another alternative is to explicitly use / declare a java8.home.

[laeubi]

The best option seems to get rid of tools.jar, so what are you really need it only for compilation as indicated in the linked issue? Then maven-jdk-tools-wrapper seems the best option + migrating your code-base to a more modern java version.

[mickaelistria]

The proper solution would be that you invest a bit in stopping to require tools.jar, so your code isn't stuck to Java 8. Java 8 isn't really supported any longer; and as you noticed, it's now getting harder and harder to get Eclipse bits properly supporting it (and there are no real chances this gets better; unless you're ready to throw tons of money to some Eclipse developers to take care of such compatibility).

However, while I don't think there is an easy or even existing solution, but some pieces are there:
First you should use the maven-toolchains-plugin or some other strategies resolving to a Maven toolchain, to explicit in your pom that you need Java 8 for your build to work. Then you can configure your toolchains.xml to define where java 8 is located. After, the critical point is to stop using ${java.home} (which is the Java running Maven, not necessarily the one you want anyway) and find a way to access the configured toolchain location.
That last part is most likely what requires a bit more work. I believe it would be good to request to Maven or to maven-toolchains-plugin a way to access toolchains information from a pom file, with a property such as ${toolchain.jdk.location} so you could use it in place of ${java.home}. Maybe there are already some existing workarounds (eg mojos) that take care of exposing toolchains info as properties; but at this stage, it's better to ask on Maven support channels directly (the more general problem is about referencing toolchain locations instead of java.home in pom files).

HTH

[glhez]

The best option seems to get rid of tools.jar, so what are you really need it only for compilation as indicated in the linked issue? Then maven-jdk-tools-wrapper seems the best option + migrating your code-base to a more modern java version.

I did not test before indicating it, but it does not work - it work in maven, but not in Eclipse, because it resolve the tools.jar against the JDK 17: you don't an error finding the dependency, but you do get compilation errors because the tools.jar was not handled by Eclipse.

You would have to add tools.jar in the Java 8 JRE (as it is not added by default) for the workspace.

This would fix the issue for those, like @demlik (the original requester) are forced to use tools.jar for whatever reasons (I only wanted to use to play with local JMX url and VirtualMachine)

Another solution would be to isolate the module requiring tools.jar and use an older version of Eclipse, but that really depends on that tools.jar is being used for.