diff --git a/lib/Db/BookmarkMapper.php b/lib/Db/BookmarkMapper.php
index c7f5c7a..6ed45ee 100644
--- a/lib/Db/BookmarkMapper.php
+++ b/lib/Db/BookmarkMapper.php
@@ -36,19 +36,22 @@ class BookmarkMapper extends ReaderMapper {
      * @param string $name
      * @return array
      */
-    public function get($fileId, $name, $type=null) {
-        $sql = "SELECT * FROM `*PREFIX*reader_bookmarks` WHERE file_id=? AND `user_id`=?";
-        $args = [ $fileId, $this->userId ];
-        if (!(null === $type)) {
-            $sql .= " AND `type`=?";
-            $args[] = $type;
-        }
-        if (!(null === $name)) {
-            $sql .= " AND `name`=?";
-            $args[] = $name;
-        }
+    public function get($fileId, $name, $type = null) {
+    	$query = $this->db->getQueryBuilder();
+    	$query->select('*')
+            ->from($this->getTableName())
+            ->where($query->expr()->eq('file_id', $query->createNamedParameter($fileId)))
+            ->andWhere($query->expr()->eq('user_id', $query->createNamedParameter($this->userId)));
 
-        return $this->findEntities($sql, $args);
+    	if ($type !== null) {
+            $query->andWhere($query->expr()->eq('type', $query->createNamedParameter($type)));
+    	}
+
+    	if ($name !== null) {
+       	    $query->andWhere($query->expr()->eq('name', $query->createNamedParameter($name)));
+    	}
+
+    	return $this->findEntities($query);
     }
 
     /**
diff --git a/lib/Db/PreferenceMapper.php b/lib/Db/PreferenceMapper.php
index 16af9be..e4db648 100644
--- a/lib/Db/PreferenceMapper.php
+++ b/lib/Db/PreferenceMapper.php
@@ -10,6 +10,7 @@
 
 namespace OCA\Epubreader\Db;
 
+use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCA\Epubreader\Utility\Time;
 use OCP\IDBConnection;
 
@@ -29,22 +30,18 @@ class PreferenceMapper extends ReaderMapper {
      * @return array
      */
     public function get($scope, $fileId, $name=null) {
-        if(!empty($name)) {
-            $sql = "SELECT * FROM `*PREFIX*reader_prefs` WHERE `scope`=? AND `file_id`=? AND `user_id`=? AND `name`=?";
-            $args = array(
-                $scope,
-                $fileId,
-                $this->userId,
-                $name);
-        } else {
-            $sql = "SELECT * FROM `*PREFIX*reader_prefs` WHERE `scope`=? AND `file_id`=? AND `user_id`=?";
-            $args = array(
-                $scope,
-                $fileId,
-                $this->userId);
+        $query = $this->db->getQueryBuilder();
+        $query->select('*')
+            ->from($this->getTableName())
+            ->where($query->expr()->eq('scope', $query->createNamedParameter($scope)))
+            ->andWhere($query->expr()->eq('file_id', $query->createNamedParameter($fileId)))
+            ->andWhere($query->expr()->eq('user_id', $query->createNamedParameter($this->userId)));
+
+        if (!empty($name)) {
+            $query->andWhere($query->expr()->eq('name', $query->createNamedParameter($name)));						   
         }
 
-        return $this->findEntities($sql, $args);
+        return $this->findEntities($query); 
     }
 
     /**
diff --git a/lib/Db/ReaderMapper.php b/lib/Db/ReaderMapper.php
index 516783a..50969a6 100644
--- a/lib/Db/ReaderMapper.php
+++ b/lib/Db/ReaderMapper.php
@@ -11,12 +11,12 @@
 namespace OCA\Epubreader\Db;
 
 use OCP\IDBConnection;
-use OCP\AppFramework\Db\Mapper;
+use OCP\AppFramework\Db\QBMapper;
 use OCP\AppFramework\Db\Entity;
 
 use OCA\Epubreader\Utility\Time;
 
-abstract class ReaderMapper extends Mapper {
+abstract class ReaderMapper extends QBMapper {
 
     /**
      * @var Time
@@ -28,12 +28,12 @@ abstract class ReaderMapper extends Mapper {
         $this->time = $time;
     }
 
-    public function update(Entity $entity) {
+    public function update(Entity $entity): Entity {
         $entity->setLastModified($this->time->getMicroTime());
         return parent::update($entity);
     }
 
-    public function insert(Entity $entity) {
+    public function insert(Entity $entity): Entity {
         $entity->setLastModified($this->time->getMicroTime());
         return parent::insert($entity);
     }