ERROR："Invalid or no mapping to system data types found" in Gateway Client

Hello experts:

         I want to use http method 'post' to upload file to internal table,and after I redefine 'create_stream' in my DPC and test it in Client,It shows "Invalid or no mapping to system data types found".

this is my MPC:

lo_entity_type = model->create_entity_type('File').

lo_entity_type->set_is_media( 'X' ).

lo_property = lo_entity_type->create_property( iv_property_name  ='Mandt    iv_abap_fieldname = 'MANDT').

lo_property = lo_entity_type->create_property( iv_property_name  ='Filename'  iv_abap_fieldname = 'FILENAME').

lo_property->set_is_key( ).

lo_property = lo_entity_type->create_property( iv_property_name  ='Sydate' iv_abap_fieldname = 'SYDATE').

lo_property = lo_entity_type->create_property( iv_property_name  ='Sytime' iv_abap_fieldname = 'SYTIME').

lo_property = lo_entity_type->create_property( iv_property_name  ='Value'  iv_abap_fieldname = 'VALUE').

lo_property = lo_entity_type->create_property( iv_property_name  ='Mimetype' iv_abap_fieldname = 'MIMETYPE').

lo_entity_type->bind_structure( 'Z_CL_MODEL_PROVIDER=>FILE' ).

lo_entity_type->create_entity_set( 'FILESET' ).

this is my DPC:

method/IWBEP/IF_MGW_APPL_SRV_RUNTIME~CREATE_STREAM.

DATA ls_excel                     TYPE ZEXCELDETAIL.

         ls_excel-mimetype = is_media_resource-mime_type.

         ls_excel-filename = iv_slug.

         ls_excel-value = is_media_resource-value.

         copy_data_to_ref( EXPORTING is_data = ls_excel

                           CHANGING  cr_data = er_entity ).

Is anyone knows how to fix with it?

Thanks!!!!!!!

Regards,

Cao