refactor

src/main/java/com/alibaba/druid/mapping/MappingEngine.java

@@ -33,6 +33,10 @@ public class MappingEngine {
         this(new MySqlMappingProvider());
     }
     
+    public MappingEngine(MappingProvider provider){
+        this.provider = provider;
+    }
+    
     public Entity getFirstEntity() {
         for (Map.Entry<String, Entity> entry : entities.entrySet()) {
             return entry.getValue();
@@ -49,10 +53,6 @@ public class MappingEngine {
         this.dataSource = dataSource;
     }
 
-    public MappingEngine(MappingProvider provider){
-        this.provider = provider;
-    }
-
     public MappingProvider getMappingProvider() {
         return provider;
     }