Make NativeImageSystemClassLoader able to handle having module classloader with a parent ClassPathClassLoader

Author: olpaw

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageClassLoaderSupport.java

@@ -102,13 +102,19 @@ public class NativeImageClassLoaderSupport {
     public final ModuleLayer moduleLayerForImageBuild;
     public final ModuleFinder modulepathModuleFinder;
 
+    static final class ClassPathClassLoader extends URLClassLoader {
+        public ClassPathClassLoader(URL[] urls, ClassLoader parent) {
+            super(urls, parent);
+        }
+    }
+
     protected NativeImageClassLoaderSupport(ClassLoader defaultSystemClassLoader, String[] classpath, String[] modulePath) {
 
         classes = EconomicMap.create();
         packages = EconomicMap.create();
         emptySet = EconomicSet.create();
 
-        classPathClassLoader = new URLClassLoader(Util.verifyClassPathAndConvertToURLs(classpath), defaultSystemClassLoader);
+        classPathClassLoader = new ClassPathClassLoader(Util.verifyClassPathAndConvertToURLs(classpath), defaultSystemClassLoader);
 
         imagecp = Arrays.stream(classPathClassLoader.getURLs())
                         .map(Util::urlToPath)

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageSystemClassLoader.java

@@ -25,11 +25,13 @@
 package com.oracle.svm.hosted;
 
 import java.io.IOException;
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
 import java.net.URL;
 import java.security.SecureClassLoader;
 import java.util.Collections;
 import java.util.Enumeration;
+import java.util.List;
 import java.util.Set;
 import java.util.WeakHashMap;
 import java.util.jar.JarFile;
@@ -135,34 +137,55 @@ public boolean isDisallowedClassLoader(ClassLoader c) {
     private static final Method defineClass = ReflectionUtil.lookupMethod(ClassLoader.class, "defineClass",
                     String.class, byte[].class, int.class, int.class);
 
-    static Class<?> loadClass(ClassLoader classLoader, String name, boolean resolve) throws ClassNotFoundException {
-        Class<?> loadedClass = null;
+    private static final Constructor<Enumeration<?>> compoundEnumerationConstructor;
+    static {
+        /* Reuse utility class defined as package-private class in java.lang.ClassLoader.java */
+        String className = "java.lang.CompoundEnumeration";
         try {
-            /* invoke the "loadClass" method on the current class loader */
-            loadedClass = ((Class<?>) loadClass.invoke(classLoader, name, resolve));
-        } catch (Exception e) {
-            if (e.getCause() instanceof ClassNotFoundException) {
-                throw ((ClassNotFoundException) e.getCause());
+            @SuppressWarnings("unchecked")
+            Class<Enumeration<?>> compoundEnumerationClass = (Class<Enumeration<?>>) Class.forName(className);
+            compoundEnumerationConstructor = ReflectionUtil.lookupConstructor(compoundEnumerationClass, Enumeration[].class);
+        } catch (ClassNotFoundException | ReflectionUtil.ReflectionUtilError e) {
+            throw VMError.shouldNotReachHere("Unable to get access to class " + className, e);
+        }
+    }
+
+    private static Class<?> loadClass(List<ClassLoader> activeClassLoaders, String name, boolean resolve) throws ClassNotFoundException {
+        ClassNotFoundException classNotFoundException = null;
+        for (ClassLoader loader : activeClassLoaders) {
+            try {
+                /* invoke the "loadClass" method on the current class loader */
+                return ((Class<?>) loadClass.invoke(loader, name, resolve));
+            } catch (Exception e) {
+                if (e.getCause() instanceof ClassNotFoundException) {
+                    classNotFoundException = ((ClassNotFoundException) e.getCause());
+                } else {
+                    String message = String.format("Can not load class: %s, with class loader: %s", name, loader);
+                    VMError.shouldNotReachHere(message, e);
+                }
             }
-            String message = String.format("Can not load class: %s, with class loader: %s", name, classLoader);
-            VMError.shouldNotReachHere(message, e);
         }
-        return loadedClass;
+        VMError.guarantee(classNotFoundException != null);
+        throw classNotFoundException;
     }
 
-    static URL findResource(ClassLoader classLoader, String name) {
-        try {
-            // invoke the "findResource" method on the current class loader
-            return (URL) findResource.invoke(classLoader, name);
-        } catch (ReflectiveOperationException e) {
-            String message = String.format("Can not find resource: %s using class loader: %s", name, classLoader);
-            VMError.shouldNotReachHere(message, e);
+    private static URL findResource(List<ClassLoader> activeClassLoaders, String name) {
+        for (ClassLoader loader : activeClassLoaders) {
+            try {
+                // invoke the "findResource" method on the current class loader
+                Object url = findResource.invoke(loader, name);
+                if (url != null)
+                    return (URL) url;
+            } catch (ReflectiveOperationException | ClassCastException e) {
+                String message = String.format("Can not find resource: %s using class loader: %s", name, loader);
+                VMError.shouldNotReachHere(message, e);
+            }
         }
         return null;
     }
 
     @SuppressWarnings("unchecked")
-    static Enumeration<URL> findResources(ClassLoader classLoader, String name) {
+    private static Enumeration<URL> findResources(ClassLoader classLoader, String name) {
         try {
             // invoke the "findResources" method on the current class loader
             return (Enumeration<URL>) findResources.invoke(classLoader, name);
@@ -186,22 +209,38 @@ static Class<?> defineClass(ClassLoader classLoader, String name, byte[] b, int
 
     @Override
     protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
-        return loadClass(getActiveClassLoader(), name, resolve);
+        return loadClass(getActiveClassLoaders(), name, resolve);
     }
 
     @Override
     protected URL findResource(String name) {
-        return findResource(getActiveClassLoader(), name);
+        return findResource(getActiveClassLoaders(), name);
     }
 
     @Override
     protected Enumeration<URL> findResources(String name) throws IOException {
-        return findResources(getActiveClassLoader(), name);
+        List<ClassLoader> activeClassLoaders = getActiveClassLoaders();
+        assert !activeClassLoaders.isEmpty() & activeClassLoaders.size() <= 2;
+        ClassLoader activeClassLoader = activeClassLoaders.get(0);
+        ClassLoader activeClassLoaderParent = activeClassLoaders.size() > 1 ? activeClassLoaders.get(1) : null;
+        if (activeClassLoaderParent != null) {
+            return newCompoundEnumeration(findResources(activeClassLoaderParent, name), findResources(activeClassLoader, name));
+        }
+        return findResources(activeClassLoader, name);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static <T> Enumeration<T> newCompoundEnumeration(Enumeration<?>... enums) {
+        try {
+            return (Enumeration<T>) compoundEnumerationConstructor.newInstance((Object) enums);
+        } catch (ReflectiveOperationException e) {
+            throw VMError.shouldNotReachHere("Cannot instantiate CompoundEnumeration", e);
+        }
     }
 
     public Class<?> forNameOrNull(String name, boolean initialize) {
         try {
-            return Class.forName(name, initialize, getActiveClassLoader());
+            return Class.forName(name, initialize, getActiveClassLoaders().get(0));
         } catch (LinkageError | ClassNotFoundException ignored) {
             return null;
         }
@@ -212,7 +251,7 @@ public Class<?> predefineClass(String name, byte[] array, int offset, int length
         if (forNameOrNull(name, false) != null) {
             throw VMError.shouldNotReachHere("The class loader hierarchy already provides a class with the same name as the class submitted for predefinition: " + name);
         }
-        return defineClass(getActiveClassLoader(), name, array, offset, length);
+        return defineClass(getActiveClassLoaders().get(0), name, array, offset, length);
     }
 
     @Override
@@ -224,11 +263,18 @@ public String toString() {
                         '}';
     }
 
-    private ClassLoader getActiveClassLoader() {
-        ClassLoader delegate = nativeImageClassLoader;
-        return delegate != null
-                        ? delegate
-                        : defaultSystemClassLoader;
+    private List<ClassLoader> getActiveClassLoaders() {
+        ClassLoader activeClassLoader = nativeImageClassLoader;
+        if (activeClassLoader != null) {
+            ClassLoader activeClassLoaderParent = activeClassLoader.getParent();
+            if (activeClassLoaderParent instanceof NativeImageClassLoaderSupport.ClassPathClassLoader) {
+                return List.of(activeClassLoader, activeClassLoaderParent);
+            } else {
+                return List.of(activeClassLoader);
+            }
+        } else {
+            return List.of(defaultSystemClassLoader);
+        }
     }
 
     /**