Added defensive null checking code to DB

Relates to https://github.com/BentoBoxWorld/BentoBox/issues/447

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

@@ -1,8 +1,5 @@
 package world.bentobox.bentobox.database.json;
 
-import world.bentobox.bentobox.BentoBox;
-import world.bentobox.bentobox.database.DatabaseConnector;
-
 import java.beans.IntrospectionException;
 import java.beans.PropertyDescriptor;
 import java.io.File;
@@ -19,6 +16,10 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Objects;
 
+import world.bentobox.bentobox.BentoBox;
+import world.bentobox.bentobox.database.DatabaseConnector;
+import world.bentobox.bentobox.database.objects.DataObject;
+
 public class JSONDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     private static final String JSON = ".json";
@@ -84,6 +85,15 @@ public class JSONDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void saveObject(T instance) throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        // Null check
+        if (instance == null) {
+            plugin.logError("JSON database request to store a null. ");
+            return;
+        }
+        if (!(instance instanceof DataObject)) {
+            plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
+            return;
+        }
         String path = DATABASE_FOLDER_NAME + File.separator + dataObject.getSimpleName();
 
         // Obtain the value of uniqueId within the instance (which must be a DataObject)
@@ -114,6 +124,16 @@ public class JSONDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void deleteObject(T instance) throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        // Null check
+        if (instance == null) {
+            plugin.logError("JSON database request to delete a null. ");
+            return;
+        }
+        if (!(instance instanceof DataObject)) {
+            plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
+            return;
+        }
+
         // Obtain the value of uniqueId within the instance (which must be a DataObject)
         PropertyDescriptor propertyDescriptor = new PropertyDescriptor("uniqueId", dataObject);
         Method method = propertyDescriptor.getReadMethod();

src/main/java/world/bentobox/bentobox/database/mongodb/MongoDBDatabaseHandler.java

@@ -15,8 +15,8 @@ import com.mongodb.client.model.Indexes;
 import com.mongodb.util.JSON;
 
 import world.bentobox.bentobox.BentoBox;
-import world.bentobox.bentobox.database.json.AbstractJSONDatabaseHandler;
 import world.bentobox.bentobox.database.DatabaseConnector;
+import world.bentobox.bentobox.database.json.AbstractJSONDatabaseHandler;
 import world.bentobox.bentobox.database.objects.DataObject;
 
 /**
@@ -78,6 +78,11 @@ public class MongoDBDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void saveObject(T instance) {
+        // Null check
+        if (instance == null) {
+            plugin.logError("MongoDB database request to store a null. ");
+            return;
+        }
         if (!(instance instanceof DataObject)) {
             plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
             return;
@@ -103,6 +108,11 @@ public class MongoDBDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void deleteObject(T instance) {
+        // Null check
+        if (instance == null) {
+            plugin.logError("MondDB database request to delete a null. ");
+            return;
+        }
         if (!(instance instanceof DataObject)) {
             plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
             return;

src/main/java/world/bentobox/bentobox/database/mysql/MySQLDatabaseHandler.java

@@ -115,6 +115,11 @@ public class MySQLDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void saveObject(T instance) {
+        // Null check
+        if (instance == null) {
+            plugin.logError("MySQL database request to store a null. ");
+            return;
+        }
         if (!(instance instanceof DataObject)) {
             plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
             return;
@@ -138,6 +143,11 @@ public class MySQLDatabaseHandler<T> extends AbstractJSONDatabaseHandler<T> {
 
     @Override
     public void deleteObject(T instance) {
+        // Null check
+        if (instance == null) {
+            plugin.logError("MySQL database request to delete a null. ");
+            return;
+        }
         if (!(instance instanceof DataObject)) {
             plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
             return;

src/main/java/world/bentobox/bentobox/database/yaml/YamlDatabaseHandler.java

@@ -34,6 +34,7 @@ import world.bentobox.bentobox.api.configuration.StoreAt;
 import world.bentobox.bentobox.api.localization.TextVariables;
 import world.bentobox.bentobox.database.AbstractDatabaseHandler;
 import world.bentobox.bentobox.database.DatabaseConnector;
+import world.bentobox.bentobox.database.objects.DataObject;
 import world.bentobox.bentobox.database.objects.adapters.Adapter;
 import world.bentobox.bentobox.database.objects.adapters.AdapterInterface;
 import world.bentobox.bentobox.util.Util;
@@ -293,6 +294,16 @@ public class YamlDatabaseHandler<T> extends AbstractDatabaseHandler<T> {
     @SuppressWarnings("unchecked")
     @Override
     public void saveObject(T instance) throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        // Null check
+        if (instance == null) {
+            plugin.logError("YAML database request to store a null. ");
+            return;
+        }
+        // DataObject check
+        if (!(instance instanceof DataObject)) {
+            plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
+            return;
+        }
         // This is the Yaml Configuration that will be used and saved at the end
         YamlConfiguration config = new YamlConfiguration();
 
@@ -547,6 +558,16 @@ public class YamlDatabaseHandler<T> extends AbstractDatabaseHandler<T> {
      */
     @Override
     public void deleteObject(T instance) throws IllegalAccessException, InvocationTargetException, IntrospectionException {
+        // Null check
+        if (instance == null) {
+            plugin.logError("YAM database request to delete a null. ");
+            return;
+        }
+        if (!(instance instanceof DataObject)) {
+            plugin.logError("This class is not a DataObject: " + instance.getClass().getName());
+            return;
+        }
+
         // Obtain the value of uniqueId within the instance (which must be a DataObject)
         PropertyDescriptor propertyDescriptor = new PropertyDescriptor("uniqueId", dataObject);
         Method method = propertyDescriptor.getReadMethod();

src/test/java/world/bentobox/bentobox/database/mysql/MySQLDatabaseHandlerTest.java

@@ -19,7 +19,7 @@ import org.bukkit.World;
 import org.bukkit.World.Environment;
 import org.bukkit.inventory.ItemFactory;
 import org.bukkit.plugin.PluginManager;
-import org.junit.BeforeClass;
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
@@ -39,7 +39,7 @@ import world.bentobox.bentobox.managers.IslandWorldManager;
 import world.bentobox.bentobox.util.Util;
 
 @RunWith(PowerMockRunner.class)
-@PrepareForTest( { BentoBox.class, Util.class })
+@PrepareForTest( { Bukkit.class, BentoBox.class, Util.class })
 public class MySQLDatabaseHandlerTest {
 
     private static MySQLDatabaseHandler<Island> handler;
@@ -52,8 +52,8 @@ public class MySQLDatabaseHandlerTest {
     private static IslandWorldManager iwm;
 
 
-    @BeforeClass
+    @Before
-    public static void setUpBeforeClass() throws Exception {
+    public void setUp() throws Exception {
         Server server = mock(Server.class);
         world = mock(World.class);
         when(server.getLogger()).thenReturn(Logger.getAnonymousLogger());
@@ -66,8 +66,7 @@ public class MySQLDatabaseHandlerTest {
         ItemFactory itemFactory = mock(ItemFactory.class);
         when(server.getItemFactory()).thenReturn(itemFactory);
 
-        Bukkit.setServer(server);
+        PowerMockito.mockStatic(Bukkit.class);
-
         when(Bukkit.getLogger()).thenReturn(Logger.getAnonymousLogger());
 
         Whitebox.setInternalState(BentoBox.class, "instance", plugin);
@@ -100,6 +99,11 @@ public class MySQLDatabaseHandlerTest {
 
     }
 
+    @Test
+    public void testSaveNullObject() {
+        handler.saveObject(null);
+    }
+
     @Test
     public void testSaveObject() {
         handler.saveObject(instance);