fix: find meta_properties_path from path or classpath (#522)

Co-authored-by: Yuqing Zhu <yuqing.zhu@139.com>

core/src/main/java/cn/edu/tsinghua/iginx/engine/physical/storage/StorageEngineClassLoader.java

@@ -79,6 +79,9 @@ protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundE
     } else {
       clazz = super.loadClass(name, resolve);
     }
+    if (clazz == null) {
+      throw new ClassNotFoundException(name);
+    }
     classMap.put(name, clazz);
     return clazz;
   }

core/src/test/java/cn/edu/tsinghua/iginx/engine/physical/storage/StorageEngineClassLoaderTest.java

@@ -0,0 +1,36 @@
+/*
+ * IGinX - the polystore system with high performance
+ * Copyright (C) Tsinghua University
+ * TSIGinX@gmail.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package cn.edu.tsinghua.iginx.engine.physical.storage;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class StorageEngineClassLoaderTest {
+  @Test
+  void testNotFound() {
+    assertThrows(
+        ClassNotFoundException.class,
+        () -> {
+          StorageEngineClassLoader classLoader = new StorageEngineClassLoader("not_found");
+          classLoader.loadClass("not_found");
+        });
+  }
+}