Flow: Support Liferay DXP 7.x (Portlet 3.0)

[pleku]

Continuation for #4760, which targets Portlet 3.0 on general level, but not any Liferay specific features. This issue is for adding automated integration testing with Liferay 7.x and enabling some Liferay specific features. If you are interested in using Liferay 7.x and Vaadin platform, please +1 this issue. If you know some specific things you'd want us to support, please add a comment here and explain _why_ would you need those.

[rlegorreta]

I've develop Liferay 7.1 with Vaadin 8 for two years. It is an excellent micro-front development environment. I would love to se some Vaadin 10+ work on Liferay 7.1+

[pleku]

We now have a prototype of running https://github.com/vaadin/addressbook-portlet using Vaadin 14.2-SNAPSHOT & slightly customized portlet addon 1.0-SNAPSHOT on Liferay 7.2.0.GA1 https://github.com/vaadin/portlet/issues/147#issuecomment-564532079, but there is at least one open question on Liferay's end that we were not able to figure out.

Also the prototype does not use any OSGi features of Liferay, so that might be something that we should be looking at separately.

So it seems that Liferay support for Vaadin 14 is technically feasible, but it has not been prioritized yet. In case you're interested in this, it would make sense to be in contact to us.

[pleku]

There is an issue open for Liferay regarding portlet 3.0 https://issues.liferay.com/browse/LPS-107438

This is still not in our plans to do anything further. If someone would want this, they should contact us about either collaboration or sponsoring for the development.

[mstahv]

If you missed it, there has been some progress! No OSGi, but for plain portlets we have somewhat working prototype now in this branch:

https://github.com/vaadin/portlet/tree/feature/liferay

You can test it for example with this branch of our addressbook demo, if you build a local snapshot from above (use -DskipTests):

https://github.com/vaadin/addressbook-portlet/tree/feature/liferay

All input would be highly appreciated!

There are couple of known issues. Maybe the most relevant is that Liferay's SPA feature needs to be disabled currently.

https://help.liferay.com/hc/en-us/articles/360030752391-Disabling-SPA