代码优化

src/main/java/org/ssssssss/magicapi/provider/impl/LowerColumnMapperProvider.java

@@ -14,6 +14,6 @@ public class LowerColumnMapperProvider implements ColumnMapperProvider {
 
 	@Override
 	public String mapping(String columnName) {
-		return columnName.toLowerCase();
+		return columnName == null ? null : columnName.toLowerCase();
 	}
 }

src/main/java/org/ssssssss/magicapi/provider/impl/UpperColumnMapperProvider.java

@@ -14,7 +14,7 @@ public class UpperColumnMapperProvider implements ColumnMapperProvider {
 
 	@Override
 	public String mapping(String columnName) {
-		return columnName.toUpperCase();
+		return columnName == null ? null : columnName.toUpperCase();
 	}
 
 }