Refactored BaseMapper and fixed bug that occurred when using foreign …

…key objects.

README.md

@@ -89,7 +89,7 @@ First, include the Maven artifact:
 <dependency>
     <groupId>com.github.collinalpert</groupId>
     <artifactId>java2db</artifactId>
-    <version>1.5.2</version>
+    <version>1.5.3</version>
 </dependency>
 ```
 Or include the [JAR](https://github.com/CollinAlpert/Java2DB/releases/) in your project. To begin using this library, you need to do two things on program start (or whenever you feel like it, it just may not work then):

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.github.collinalpert</groupId>
     <artifactId>java2db</artifactId>
-    <version>1.5.2</version>
+    <version>1.5.3</version>
     <packaging>jar</packaging>
 
     <name>Java2DB</name>

src/main/java/com/github/collinalpert/java2db/mappers/BaseMapper.java

@@ -14,7 +14,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
-import java.util.stream.Collectors;
 
 /**
  * @author Collin Alpert
@@ -60,10 +59,10 @@ public Optional<T> map(ResultSet set) {
 	 * @return A list of Java entities.
 	 */
 	public List<T> mapToList(ResultSet set) {
-		List<T> list = new ArrayList<>();
+		var list = new ArrayList<T>();
 		try {
 			while (set.next()) {
-				T entity = IoC.resolve(clazz);
+				var entity = IoC.resolve(clazz);
 				setFields(set, entity);
 				list.add(entity);
 			}
@@ -86,33 +85,35 @@ private void setFields(ResultSet set, T entity) throws IllegalAccessException {
 		var fields = Utilities.getAllFields(entity, true);
 		try {
 			var foreignKeys = getForeignKeys(fields, set);
-			var foreignKeyObjects = getForeignKeyObjects(fields);
 			for (var field : fields) {
 				field.setAccessible(true);
-				if (field.getAnnotation(ForeignKeyObject.class) != null) {
-					ForeignKeyObject fkObjectNumber = field.getAnnotation(ForeignKeyObject.class);
-					Class<?> clz = foreignKeyObjects.keySet().stream().filter(x -> x == field.getType()).findFirst().orElseThrow();
-					var service = IoC.resolveServiceByEntity((Class<? extends BaseEntity>) clz);
-					var fkObject = service.getById(foreignKeys.get(fkObjectNumber.value()));
-					if (fkObject.isPresent()) {
-						field.set(entity, fkObject.get());
-					} else {
+				ForeignKeyObject foreignKeyObject;
+				if ((foreignKeyObject = field.getAnnotation(ForeignKeyObject.class)) != null) {
+					if (!BaseEntity.class.isAssignableFrom(field.getType())) {
+						throw new IllegalArgumentException(String.format("Foreign key object %s with id %d does not extend BaseEntity.", field.getType(), foreignKeyObject.value()));
+					}
+					var service = IoC.resolveServiceByEntity((Class<? extends BaseEntity>) field.getType());
+					var optionalEntity = service.getById(foreignKeys.get(foreignKeyObject.value()));
+					if (!optionalEntity.isPresent()) {
 						System.err.printf("Could not set type %s with name %s\n", field.getType(), field.getName());
+						continue;
 					}
+					field.set(entity, optionalEntity.get());
 					continue;
 				}
 				var value = set.getObject(field.getName(), field.getType());
 				field.set(entity, value);
-
 			}
 		} catch (SQLException e) {
 			e.printStackTrace();
+			//TODO add possibility of custom mapping classes.
 			throw new IllegalArgumentException("Cannot use base mapping. Please define custom mapping in according mapping class.");
 		}
 	}
 
+
 	/**
-	 * @param fields List of fields to get the foreign key annotations from.
+	 * @param fields Map of fields to get the foreign key annotations from.
 	 * @param set    The {@link ResultSet} is needed to get the actual foreign key.
 	 * @return A {@link Map} where the keys are the id number of this foreign key and the values are the actual foreign keys.
 	 * @throws SQLException when the foreign key in the {@link ResultSet} does not exist.
@@ -127,15 +128,4 @@ private Map<Integer, Integer> getForeignKeys(ArrayList<Field> fields, ResultSet
 		}
 		return map;
 	}
-
-	/**
-	 * Gets the classes of all fields that represent a foreign key object, i.e. do not exist on the database.
-	 *
-	 * @param fields A list of fields to get the foreign key objects from.
-	 * @return A {@link Map} where the keys are the classes of the foreign keys and the value is the id number for this foreign key.
-	 */
-	private Map<Class<?>, Integer> getForeignKeyObjects(ArrayList<Field> fields) {
-		return fields.stream().filter(field -> field.getAnnotation(ForeignKeyObject.class) != null)
-				.collect(Collectors.toMap(Field::getType, field -> field.getAnnotation(ForeignKeyObject.class).value()));
-	}
 }

src/main/java/com/github/collinalpert/java2db/services/BaseService.java

@@ -56,6 +56,8 @@ public BaseService(Class<T> clazz) {
 	 * Creates this Java entity on the database.
 	 *
 	 * @param instance The instance to create on the database.
+	 * @throws SQLException if the query cannot be executed due to database constraints
+	 *                      i.e. non-existing default value for field or an incorrect data type.
 	 */
 	public void create(T instance) throws SQLException {
 		var insertQuery = new StringBuilder("insert into `").append(tableName).append("` (");
@@ -180,6 +182,8 @@ public List<T> getAll() {
 	 * Updates this entity's row on the database.
 	 *
 	 * @param instance The instance to update on the database.
+	 * @throws SQLException if the query cannot be executed due to database constraints
+	 *                      i.e. non-existing default value for field or an incorrect data type.
 	 */
 	public void update(T instance) throws SQLException {
 		var updateQuery = new StringBuilder("update `").append(tableName).append("` set ");