[I] DynMethods.Builder.ctorImpl ignores the builder's configured ClassLoader [kyuubi]

["LuciferYang (via GitHub)" <gi...@apache.org>]

LuciferYang opened a new issue, #7688:
URL: https://github.com/apache/kyuubi/issues/7688

   ### Description
   
   `DynMethods.Builder` lets a caller choose the loader used for name-based lookups:
   
   ```java
   public Builder loader(ClassLoader newLoader) {
     this.loader = newLoader;
     return this;
   }
   ```
   
   `impl(String className, ...)` honours it:
   
   ```java
   Class<?> targetClass = Class.forName(className, true, loader);
   ```
   
   `ctorImpl(String className, ...)` does not. It builds a fresh inner `DynConstructors.Builder`, whose own `loader` field defaults to `Thread.currentThread().getContextClassLoader()`, and never forwards the one configured on the outer builder:
   
   ```java
   this.method = new DynConstructors.Builder().impl(className, argClasses).buildChecked();
   ```
   
   So `.loader(x).ctorImpl("some.Class")` resolves `some.Class` through the thread context loader rather than through `x`. When the context loader cannot see the class, `DynConstructors.Builder.impl(String, ...)` swallows the `ClassNotFoundException` as a candidate miss, and the outer `build()` / `buildChecked()` then fails with a generic cannot-find error. The configured loader is ignored without any diagnostic saying so.
   
   This matters in Kyuubi because engine code reflects into classes that are only visible to a particular loader (a Spark or Flink user classloader, an isolated engine classloader), and `.loader(...)` is the documented way to name that loader.
   
   Reproducer:
   
   ```java
   ClassLoader appLoader = MyClass.class.getClassLoader();
   ClassLoader blinded = new URLClassLoader(new URL[0], null);
   Thread.currentThread().setContextClassLoader(blinded);
   
   DynMethods.builder("MyClass")
       .loader(appLoader)                  // ignored
       .ctorImpl(MyClass.class.getName())
       .buildChecked();
   
   // java.lang.NoSuchMethodException: Cannot find method: MyClass
   ```
   
   Expected: the constructor is found, because `appLoader` can see `MyClass`.
   
   ### Affected code
   
   `DynMethods.Builder.ctorImpl(String, Class...)`. The `ctorImpl(Class, Class...)` overload takes an already-loaded class and its inner lookup only calls `Class.getConstructor`, so it never reads a loader and is unaffected.
   
   ### Upstream
   
   Neither upstream copy forwards the loader either: parquet-common has the same shape on 1.12.x and on current master, and iceberg-common had it on 0.12.1 before removing `ctorImpl` altogether. Note that `ctorImpl` currently has no callers inside Kyuubi, so an alternative to fixing it is to follow iceberg and drop both overloads; that is a maintainer call.
   


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Re: [I] DynMethods.Builder.ctorImpl ignores the builder's configured ClassLoader [kyuubi]

["pan3793 (via GitHub)" <gi...@apache.org>]

pan3793 closed issue #7688: DynMethods.Builder.ctorImpl ignores the builder's configured ClassLoader
URL: https://github.com/apache/kyuubi/issues/7688


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