[FIXED] How to make Eclipse RUN patched JRE modules on JDK9+ with the —patch-module java option

Issue

This SO question asks how to get Eclipse to compile with the —patch-module javac option.

However, I have found no obvious and easy way to get Eclipse to run the compiled patched code using the same configuration.

i.e. to use the Build Path / Module Dependencies configuration described in the question above at Run / Debug time too.

After much fruitless hunting, I resorted to adding "—patch-module xxxx" to the Launch “Debug Configurations / Arguments / VM Arguments” to point to the folder containing the classes compiled by Eclipse. e.g.

--patch-module java.security.jgss=/Users/xxx/svn/JGSSDebug/bin

That worked, but is a bit brute force! Is there an easier way that I have missed?

Edit1

One can use Java Build Path / Module Dependencies / Show JPMS Options from the project JGSSDebug to get the correct command line syntax, and manually paste to the VM Arguments of the Launch Configuration of the project JGSSDebug-Test. (...just don't forget to change "src" to "bin" at the end of the path ...). The first time round I worked the syntax myself.

End Edit1

I am running Eclipse Version: 2021-03 (4.19.0) Build id: 20210312-0638

Background:

In order to troubleshoot problems with SPNEGO SSO we want to enrich classes in the JRE module java.security.jgss with additional log output.

I have created two Eclipse Projects:

1. JGSSDebug This project contains the java.security.jgss classes we will patch with log output. The .classpath file contains:

   <attribute name="patch-module" value="java.security.jgss=/JGSSDebug"/>'
   

2. JGSSDebug-Test This project will call code in java.security.jgss including the patched code in JGSSDebug. It depends on JGSSDebug:

   <classpathentry combineaccessrules="false" kind="src" path="/JGSSDebug"/>
   

The only way I could find to make JGSSDebug-Test run the patched code was via the “VM Arguments” as described above.

Neither project has a module-info.java file.

We are using Azul OpenJDK 11.0.11 to compile and run.

Solution

It does not work with dependent projects. Each project has its own and exclusive Project > Properties: Java Build Path > Module Dependencies settings.

There seems to be an issue in the current version of Eclipse: in the Module Dependencies tab, when hitting the Show JPMS Options... buttons, the correct --patch-module java.security.jgss=... will be shown, but in the launch configuration these JPMS options are missing. Please make sure, this has been reported to Eclipse JDT.

As alternative or workaround, to avoid to specify --patch-module java.security.jgss=... in each launch configuration, add it as default VM argument to the JRE/JDK:

1. In the preferences Java > Installed JREs choose the JRE/JDK used in your project and hit Edit...
2. As Default VM argument enter the following:
   --patch-module java.security.jgss=${workspace_loc:/JGSSDebug/bin}

Answered By - howlger