Avoid trying to load files starting with ._

src/main/java/world/bentobox/bentobox/database/json/JSONDatabaseHandler.java

@@ -56,7 +56,7 @@ public List<T> loadObjects() {
             tableFolder.mkdirs();
         }
         // Load each object from the file system, filtered, non-null
-        for (File file: Objects.requireNonNull(tableFolder.listFiles((dir, name) ->  name.toLowerCase(Locale.ENGLISH).endsWith(JSON)))) {
+        for (File file: Objects.requireNonNull(tableFolder.listFiles((dir, name) ->  name.toLowerCase(Locale.ENGLISH).endsWith(JSON) && !name.startsWith("._")))) {
             try (FileReader reader = new FileReader(file)){
                 T object = getGson().fromJson(reader, dataObject);
                 if (object != null) {

src/test/java/world/bentobox/bentobox/database/json/JSONDatabaseHandlerTest.java

@@ -0,0 +1,177 @@
+package world.bentobox.bentobox.database.json;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.when;
+
+import java.beans.IntrospectionException;
+import java.io.File;
+import java.lang.reflect.InvocationTargetException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+
+import org.bukkit.Bukkit;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.powermock.api.mockito.PowerMockito;
+import org.powermock.core.classloader.annotations.PrepareForTest;
+import org.powermock.modules.junit4.PowerMockRunner;
+import org.powermock.reflect.Whitebox;
+
+import com.google.gson.annotations.Expose;
+
+import world.bentobox.bentobox.BentoBox;
+import world.bentobox.bentobox.database.DatabaseConnector;
+import world.bentobox.bentobox.database.objects.DataObject;
+import world.bentobox.bentobox.util.Util;
+
+/**
+ * Test class
+ * @author tastybento
+ */
+@RunWith(PowerMockRunner.class)
+@PrepareForTest( { Bukkit.class, BentoBox.class, Util.class })
+public class JSONDatabaseHandlerTest {
+
+    @Mock
+    private BentoBox plugin;
+    @Mock
+    private DatabaseConnector connector;
+    private TestClass test;
+
+    private JSONDatabaseHandler<TestClass> handler;
+
+    /**
+     * @throws java.lang.Exception
+     */
+    @Before
+    public void setUp() throws Exception {
+        // Setup plugin
+        Whitebox.setInternalState(BentoBox.class, "instance", plugin);
+        when(plugin.isEnabled()).thenReturn(false);  // Force sync actions
+        //Bukkit
+        PowerMockito.mockStatic(Bukkit.class, Mockito.RETURNS_MOCKS);
+
+        test = new TestClass();
+        test.setUniqueId("test");
+        handler = new JSONDatabaseHandler<>(plugin, TestClass.class, connector);
+    }
+
+    class TestClass implements DataObject {
+
+        @Expose
+        private String uniqueId;
+
+        @Override
+        public String getUniqueId() {
+            return uniqueId;
+        }
+
+        @Override
+        public void setUniqueId(String uniqueId) {
+            this.uniqueId = uniqueId;
+
+        }
+
+    }
+
+    /**
+     * @throws java.lang.Exception
+     */
+    @After
+    public void tearDown() throws Exception {
+        // Clean up the folders
+        File dataFolder = new File("database");
+        if (dataFolder.exists()) {
+            Files.walk(dataFolder.toPath())
+            .sorted(Comparator.reverseOrder())
+            .map(Path::toFile)
+            .forEach(File::delete);
+        }
+        dataFolder = new File("database_backup");
+        if (dataFolder.exists()) {
+            Files.walk(dataFolder.toPath())
+            .sorted(Comparator.reverseOrder())
+            .map(Path::toFile)
+            .forEach(File::delete);
+        }
+        Mockito.framework().clearInlineMocks();
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.database.json.JSONDatabaseHandler#loadObjects()}.
+     * @throws IntrospectionException 
+     * @throws InvocationTargetException 
+     * @throws IllegalAccessException 
+     */
+    @Test
+    public void testLoadObjects() throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        assertTrue(handler.loadObjects().isEmpty());
+        handler.saveObject(test);
+        assertEquals(test.getUniqueId(), handler.loadObjects().getFirst().getUniqueId());
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.database.json.JSONDatabaseHandler#loadObject(java.lang.String)}.
+     * @throws IntrospectionException 
+     * @throws InvocationTargetException 
+     * @throws IllegalAccessException 
+     */
+    @Test
+    public void testLoadObject() throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        assertNull(handler.loadObject("test"));
+        handler.saveObject(test);
+        assertEquals(test.getUniqueId(), handler.loadObject("test").getUniqueId());
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.database.json.JSONDatabaseHandler#deleteObject(java.lang.Object)}.
+     * @throws IntrospectionException 
+     * @throws InvocationTargetException 
+     * @throws IllegalAccessException 
+     */
+    @Test
+    public void testDeleteObject() throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        handler.saveObject(test);
+        assertNotNull(handler.loadObject("test"));
+        handler.deleteObject(test);
+        assertNull(handler.loadObject("test"));
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.database.json.JSONDatabaseHandler#objectExists(java.lang.String)}.
+     * @throws IntrospectionException 
+     * @throws InvocationTargetException 
+     * @throws IllegalAccessException 
+     */
+    @Test
+    public void testObjectExists() throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        assertFalse(handler.objectExists("test"));
+        when(connector.uniqueIdExists(anyString(), anyString())).thenReturn(true);
+        assertTrue(handler.objectExists("test"));
+    }
+
+    /**
+     * Test method for {@link world.bentobox.bentobox.database.json.JSONDatabaseHandler#deleteID(java.lang.String)}.
+     * @throws IntrospectionException 
+     * @throws InvocationTargetException 
+     * @throws IllegalAccessException 
+     */
+    @Test
+    public void testDeleteID() throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        assertNull(handler.loadObject("test"));
+        handler.saveObject(test);
+        handler.deleteID("test");
+        assertNull(handler.loadObject("test"));
+    }
+
+}