DATACMNS-1066 - ClassGeneratingPropertyAccessorFactory now opts out on failed access to ClassLoader.

We now eagerly check the accessibility of the defineClass(…) method on the class loader to be used for a PersistentEntity. This will then cause the clients to use a different PropertyAccessorFactory (as things stand today: the one using reflection) and not fail to create the class later on.

src/main/java/org/springframework/data/mapping/model/ClassGeneratingPropertyAccessorFactory.java

@@ -36,7 +36,6 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.springframework.asm.ClassWriter;
@@ -44,7 +43,6 @@ import org.springframework.asm.Label;
 import org.springframework.asm.MethodVisitor;
 import org.springframework.asm.Opcodes;
 import org.springframework.asm.Type;
-import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
@@ -94,8 +92,8 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 	 * Checks whether an accessor class can be generated.
 	 *
 	 * @param entity
-	 * @return {@literal true} if the runtime is equal or greater to Java 1.7, property name hash codes are unique and the
-	 *         type has a class loader we can use to re-inject types.
+	 * @return {@literal true} if the runtime is equal or greater to Java 1.7, we can access the ClassLoader, the property
+	 *         name hash codes are unique and the type has a class loader we can use to re-inject types.
 	 * @see PersistentPropertyAccessorFactory#isSupported(PersistentEntity)
 	 */
 	@Override
@@ -103,6 +101,12 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 
 		Assert.notNull(entity, "PersistentEntity must not be null!");
 
+		try {
+			Evil.getClassLoaderMethod(entity);
+		} catch (Exception o_O) {
+			return false;
+		}
+
 		if (entity.getType().getClassLoader() == null || entity.getType().getPackage().getName().startsWith("java")) {
 			return false;
 		}
@@ -1432,6 +1436,7 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 	 * accessed from a class in the same class loader.
 	 *
 	 * @author Mark Paluch
+	 * @author Oliver Gierke
 	 */
 	@UtilityClass
 	private static class Evil {
@@ -1446,25 +1451,30 @@ public class ClassGeneratingPropertyAccessorFactory implements PersistentPropert
 		 * @param persistentEntity
 		 * @return
 		 */
-		@SuppressWarnings("rawtypes")
 		Class<?> defineClass(String name, byte[] bytes, int offset, int len, PersistentEntity<?, ?> persistentEntity) {
 
 			ClassLoader classLoader = persistentEntity.getType().getClassLoader();
-			Class<?> classLoaderClass = classLoader.getClass();
 
 			try {
 
-				Class<? extends PersistentEntity> persistentEntityClass = persistentEntity.getClass();
-				Method defineClass = ReflectionUtils.findMethod(classLoaderClass, "defineClass", String.class, byte[].class,
-						Integer.TYPE, Integer.TYPE, ProtectionDomain.class);
+				Method defineClass = getClassLoaderMethod(persistentEntity);
 				defineClass.setAccessible(true);
 
 				return (Class<?>) defineClass.invoke(classLoader, name, bytes, offset, len,
-						persistentEntityClass.getProtectionDomain());
+						persistentEntity.getClass().getProtectionDomain());
 
 			} catch (ReflectiveOperationException e) {
 				throw new IllegalStateException(e);
 			}
 		}
+
+		static Method getClassLoaderMethod(PersistentEntity<?, ?> entity) {
+
+			ClassLoader classLoader = entity.getType().getClassLoader();
+			Class<?> classLoaderClass = classLoader.getClass();
+
+			return ReflectionUtils.findMethod(classLoaderClass, "defineClass", String.class, byte[].class, Integer.TYPE,
+					Integer.TYPE, ProtectionDomain.class);
+		}
 	}
 }