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Unlike the servlet world, these requests must be broken up into the separate portlet requests.

A file upload is an action request.

A response showing an error is a render request.

A file download is a resource request.

See them as the individual parts they must be, then it should be clearer how to proceed...

The upload receives the CSV and does the processing, perhaps keeping the file or the data or perhaps it goes all the way and builds the xls, but it can't return anything. It can, however, pass around request attributes so it can share the fact that the error has occurred and perhaps relevant keys for download.

The render request is handled by a JSP page (in Liferay MVC but could be any render technology you are using) which shows that an error has occurred and the link to download the xls, created as a resource URL and tied to the interface element.

The resource handler is used to return the xls. Perhaps this was already pre-built by the upload, but me, I'd actually delay and build the XLS on demand in the serve resource method. You never really know if someone will click the link to pull the file or not. The bigger question is whether you need to persist the XLS (so you only build one for many downloads or you build on demand so there is no storage requirement but if 100 people click the link you're recreating the file 100 times).

Either way, everything has been broken down to the point where it is clear how to proceed with the portlet implementation.

It was just a question of separating into the proper portlet request flow.

Hello Devid,

Thanks for your valuable response.

in my scenario, I have below screen:

  

Here, I'm uploading CSV just for bulk data upload. I don't want to save csv at all.


Once I'm Getting data at server side from csv. I don't need the CSV furthermore.

After data unwrapped from csv. I have a mechanism to validate them.

During the validation process If data is not valid then only the entire csv data transferred to .xls(Excel) file and the same file will download
to the user who uploaded it.

The purpose of this downloading is to show the faulty record to the user who uploaded the csv.

Else data insert to the database table.

I don't need csv and xls at all for future use. Also, No one will allow to downloading same xls file or csv file again.


Process :

Step1: upload csv file.

Step2: Validate data

          if data is valid
                 Insert data in table
          else 
              -->>> create xls from csv data
              -->>> donwload xls to user who uploaded csv.
finish

How could I handle this ?