AppToAppSSO between HTML5 AND Java proxy for Document Service

[Epena]

Hello All,

I've created a Java proxy as explained by SAP here:

https://help.sap.com/viewer/b0cc1109d03c4dc299c215871eed8c42/Cloud/en-US/ed1c6732d4214c68846ab9813b9...

Then I've created an HTTP Destination on SCP for use within my HTML5 app to connect to document service.

If I set authentication mode to "Basic" and explicitly type username/password everything works fine from my SAPUI5 app, however, this is not the desired method, I want it to automatically pass credentials of authenticated users to the java app, however, whenever I use "AppToAppSSO" as authentication method on the destination, it prompts for user/password whenever I try to access the document service through proxy java app, even though I've already authenticated to the SAPUI5 app.

Any ideas why this is happening and how to solve it?

Regards.