fixes NPE issues reported in #203

Author: anidotnet

nitrite/src/main/java/org/dizitart/no2/exceptions/ErrorCodes.java

@@ -113,6 +113,7 @@ public class ErrorCodes {
     public static final int VE_OBJ_STORE_EMPTY_KEY = 1085;
     public static final int VE_FIND_NOT_IN_INDEX_NULL_FIELD = 1086;
     public static final int VE_FIND_NOT_IN_INDEX_NULL_VALUE = 1087;
+    public static final int VE_OBJ_REMOVE_NULL_OBJECT = 1088;
 
     /* NitriteIOException Codes */
     public static final int NIOE_DATABASE_OPENED = 2001;

nitrite/src/main/java/org/dizitart/no2/objects/DefaultObjectRepository.java

@@ -158,6 +158,7 @@ public WriteResult update(ObjectFilter filter, Document update, boolean justOnce
 
     @Override
     public WriteResult remove(T element) {
+        notNull(element, errorMessage("element can not be null", VE_OBJ_REMOVE_NULL_OBJECT));
         if (idField == null) {
             throw new NotIdentifiableException(OBJ_REMOVE_FAILED_AS_NO_ID_FOUND);
         }

nitrite/src/test/java/org/dizitart/no2/EdgeCases.java

@@ -4,10 +4,12 @@
 import org.dizitart.no2.objects.ObjectRepository;
 import org.dizitart.no2.objects.data.Employee;
 import org.dizitart.no2.objects.data.Note;
+import org.dizitart.no2.objects.data.WithNitriteId;
 import org.dizitart.no2.objects.filters.ObjectFilters;
 import org.junit.Test;
 
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 
 /**
  * @author Anindya Chatterjee
@@ -34,6 +36,14 @@ public void testDeleteIteratorNPE() {
 
     @Test
     public void testDelete() {
-        Employee employee = employeeRepository.find().firstOrDefault();
+        ObjectRepository<WithNitriteId> repo = db.getRepository(WithNitriteId.class);
+        WithNitriteId one = new WithNitriteId();
+        one.setName("Jane");
+        repo.insert(one);
+
+        WithNitriteId note = repo.find().firstOrDefault();
+        repo.remove(note);
+
+        assertNull(repo.getById(one.idField));
     }
 }

nitrite/src/test/java/org/dizitart/no2/objects/NitriteIdAsIdTest.java

@@ -18,11 +18,11 @@
 
 package org.dizitart.no2.objects;
 
-import lombok.Data;
 import org.dizitart.no2.Nitrite;
 import org.dizitart.no2.NitriteId;
 import org.dizitart.no2.WriteResult;
 import org.dizitart.no2.exceptions.InvalidIdException;
+import org.dizitart.no2.objects.data.WithNitriteId;
 import org.dizitart.no2.util.Iterables;
 import org.junit.After;
 import org.junit.Before;
@@ -106,10 +106,4 @@ public void changeIdDuringUpdate() {
         assertEquals(repo.size(), 1);
     }
 
-    @Data
-    private static class WithNitriteId {
-        @Id
-        private NitriteId idField;
-        private String name;
-    }
 }

nitrite/src/test/java/org/dizitart/no2/objects/data/WithNitriteId.java

@@ -0,0 +1,15 @@
+package org.dizitart.no2.objects.data;
+
+import lombok.Data;
+import org.dizitart.no2.NitriteId;
+import org.dizitart.no2.objects.Id;
+
+/**
+ * @author Anindya Chatterjee
+ */
+@Data
+public class WithNitriteId {
+    @Id
+    public NitriteId idField;
+    public String name;
+}