> Can I please get a review of this doc-only change which proposes to add an
> `@apiNote` on the constructors of `URLClassLoader` and `SecureClassLoader` to
> explain the current implementation of these constructors? This addresses
> https://bugs.openjdk.org/browse/JDK-8228773?
>
> As noted in that issue, this updated documentation is to help applications be
> aware that a `null` value which represents the bootstrap class loader when
> passed for `parent` class loader will mean that the constructed
> `URLClassLoader` may not be able to load all platform classes.
>
> Specifically, only a specific set of modules are mapped (at JDK build time)
> to the bootstrap class loader. Some modules like `java.sql` are visible to
> the platform class loader but not to the bootstrap classloader. The
> distinction between these class loaders is explained in the API documentation
> of `ClassLoader` class
> https://docs.oracle.com/en/java/javase/24/docs/api/java.base/java/lang/ClassLoader.html#builtinLoaders.
>
> Using `null` (which represents a bootstrap class loader) for `parent` when
> constructing the `URLClassLoader` then means that the class loader would not
> be able to load some of these platform classes. For example, consider:
>
>
> import java.net.*;
>
> public class Test {
> public static void main(String[] args) throws Exception {
> System.out.println("testing against Java " +
> System.getProperty("java.version"));
>
> final ClassLoader cl = new URLClassLoader(new URL[0], null);
> final Class<?> klass = cl.loadClass("java.sql.ResultSet"); // load a
> platform class that belongs to the java.sql module
> System.out.println("loaded " + klass + " using classloader: " +
> klass.getClassLoader());
>
> }
> }
>
> which constructs the `URLClassLoader` with the bootstrap class loader as its
> parent and then attempts to load a platform class `java.sql.ResultSet`. Since
> this class' module is mapped to the platform class loader and not the
> bootstrap class loader, running this code against Java 9+ will result in a
> `ClassNotFoundException`:
>
>
> testing against Java 24
> Exception in thread "main" java.lang.ClassNotFoundException:
> java.sql.ResultSet
> at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:349)
> at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:557)
> at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:490)
> at Test.main(Test.java:8)
>
>
> No new tests have been introduced and existing tests in tier1, tier2 and
> tier3 continue to pass.
>
> Once we settle on th...
Jaikiran Pai has updated the pull request incrementally with three additional
commits since the last revision:
- replace system class loader reference with bootstrap class loader
- remove "the"
- {@code null} instead of null
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/25517/files
- new: https://git.openjdk.org/jdk/pull/25517/files/12f70566..9897bec3
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=25517&range=03
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=25517&range=02-03
Stats: 18 lines in 2 files changed: 0 ins; 0 del; 18 mod
Patch: https://git.openjdk.org/jdk/pull/25517.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/25517/head:pull/25517
PR: https://git.openjdk.org/jdk/pull/25517
