Retrieving PLATFORM_CLASS_PATH from file manager

[Jonathan Gibbons]

On 09/13/2015 06:25 AM, Alan Bateman wrote:
> On 12/09/2015 20:16, Jayaprakash Arthanareeswaran wrote:
>>
>> Hello experts,
>>
>> With JDK 9, some of JDT Core tests have started failing. The failing 
>> tests
>> are in the JSR 199 area, where we test Eclipse's compiler in a mixed 
>> mode
>> with Javac's StandardJavaFileManager.
>>
>> standardJavaFileManager.getLocation(StandardLocation.PLATFORM_CLASS_PATH); 
>>
>>
>> Until JDK 8, this used to return rt.jar and other jars but not 
>> anymore. I
>> expected this to return the path to the bootmodules.jimage just like the
>> system property "sun.boot.class.path".
>>
> The proposal is to drop sun.boot.class.path, see the "Removed: 
> Bootstrap class-path options" in JEP 261 [1]. It wasn't been useful 
> since the changes for JEP 220 went into JDK 9. There are a few 
> remaining pieces to be done in HotSpot before we can get there, mostly 
> in the Serviceability Agent and the "Compile-The-World" built-in test. 
> The issue is tracked by JDK-8131049 and JDK-8077209.
>
> To be consistent then I would think getLocation(PLATFORM_CLASS_PATH) 
> would return an empty Iterable and a getLocation(SYSTEM_MODULE_PATH), 
> or a Iterable<Path> variant, would return jrt:/.  I'm sure Jon will 
> reply on this issue and explain JRT_MARKER_FILE (which I suspect is 
> what you are wondering about).
>
> -Alan
>
> [1] http://openjdk.java.net/jeps/261

There are two aspects to this.

JavaFileManager does not know the details of how it is being used, and 
so it does not know whether it is being used in a "legacy" compilation 
using PLATFORM_CLASS_PATH, or in a "modular" compilation" using 
SYSTEM_MODULE_PATH.  Therefore both the PLATFORM_CLASS_PATH and 
SYSTEM_MODULE_PATH locations are defined, for use as the context dictates.

We are also updating StandardJavaFileManager to better support 
Path-based locations, as well as File-based locations. JRT_MARKER_FILE 
is a remnant of that transition, and that of introducing jrt-fs to JDK 8 
and JDK 9.

-- Jon