RFR: 8315130: java.lang.IllegalAccessError when processing classlist to create CDS archive [v3]

[Ioi Lam]

On Fri, 4 Apr 2025 18:17:14 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> src/java.base/share/classes/jdk/internal/misc/CDS.java line 420:
>> 
>>> 418:                 // class loader. Thus it is safe to delegate their loading to system class loader
>>> 419:                 // (our parent) - this is what the default implementation of loadClass() will do.
>>> 420:                 return (Class<?>) DEFINE_CLASS.invoke(this, name, res);
>> 
>> Instead of subclassing from `URLClassLoader` and go through the trouble of calling its `defineClass()` method, maybe we should just subclass from `ClassLoader` and maintain a hashtable of java.util.jar.JarFiles.
>> 
>> 
>> HashMap<String, JarFile> map = ....;
>> JarFile jar = map.get(source) ... or open a new JarFile if not found
>> byte[] buffer = read jar file for the given class name;
>> call ClassLoader.defineClass(buffer, ...)
>
> All the opening and reading is handled by `URLClassPath` (it's not just JARs, can also be directories). I used only `defineClass` from `URLClassLoader` to minimize the behavior difference with the old code — besides defining the class it defines its package and protection domain. But it looks like static CDS strips these anyway, so I've removed `URLClassLoader` entirely.
> 
> `URLClassPath` usage can also be removed — then the small addition to it from this PR won't be needed but its functionality will be somewhat duplicated in `CDS.UnregisteredLoader`. I've implemented this [in a separate branch](https://github.com/openjdk/jdk/compare/master...TimPushkin:jdk:one-loader-v2?expand=1).

I prefer the changes in your separate branch. URLClassPath is intended for sequential access. Adding the new method for random access could introduce extraneous requirements that might affect future evolution of URLClassPath. As the code for JarSource and Dir Source is quite small, I think it's acceptable.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24223#discussion_r2029438393