Add more flexibility for loading a DTFJ implementation

[eclipsewebmaster]

| --- | --- | | Bugzilla Link | 567819 | | Status | NEW | | Importance | P3 normal | | Reported | Oct 12, 2020 18:50 EDT | | Modified | Nov 29, 2022 09:23 EDT | | See also | Gerrit change 170676, Gerrit change 189638 | | Reporter | Kevin Grigorenko |

Description

This is a follow-on to bug 558984; although that was resolved with an updated IBM DTFJ plugin, there have been other issues related to loading Java 11 dumps and OpenJ9 dumps. The DTFJ plugin system does allow multiple plugins in theory, but that just has to brute force search for one that works, and issues often arise related to non-fatal parsing errors. Therefore, it would be nice to give users more flexibility in choosing which DTFJ is used to parse a J9 dump.

This bug proposes adding flexibility to the DTFJ plugin system:

1. For Java 8, allow users to specify explicit directories containing dtfj.jar and j9ddr.jar.
2. For Java > 8, allow users to load DTFJ from the running JVM rather than the DTFJ plugin.
3. For backwards compatibility, continue to prefer the IBM DTFJ plugin if available.
4. Allow users to load J9 dumps without the IBM DTFJ plugin if the JVM has DTFJ.