Writing first Liferay application: how to deploy module to server + error: A full JDK (not just JRE) is required

Question

I'm following Liferay getting-started example to develop my first we app with Liferay IDE in which it is mentioned:

Even though all you’ve done is generate it, the guestbook-web project is ready to be built and deployed to Liferay DXP. Make sure that your server is running, and if it isn’t, select it in Developer Studio’s Servers pane and click the start button. After it starts, drag and drop the guestbook-web project from the Project Explorer to the server.

I started the server, however, I don't know how to deploy guestbook-web module to server. Drag and drop is not working for me:

When Opening the web page, this is shown which doesn't contain anything related to guestbook-web module:

Update

When I drag and drop my module on server, for some reason it is not allowed:

Update

Also, I'm receiving such errors on console:

22-Apr-2020 16:02:54.419 SEVERE [http-nio-8080-exec-6] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [Module Framework Servlet] in context with path [] threw exception [PWC6345: There is an error in invoking javac.  A full JDK (not just JRE) is required] with root cause
 org.apache.jasper.JasperException: PWC6345: There is an error in invoking javac.  A full JDK (not just JRE) is required

I have set both JDK and JRE path for IDE, not sure why it says A full JDK (not just JRE) is required.

Update

To fix A full JDK (not just JRE) is required error, inspired by this answer, I ran the IDE with this command:

C:\Program Files (x86)\LiferayWorkspacewithDevStudioCommunityEdition\liferay-developer-studio>DeveloperStudio.exe -vm "C:\Program Files\Java\jdk1.8.0_251\bin\javaw.exe"

The error is resolved and default widgets are fine now:

Olaf Kock · Accepted Answer · 2020-04-23T08:03:16.430

In the IDE: You'll drag the "guestbook-web" with the mouse and drop it right on the highlighted "Liferay 7.x at localhost" Server (Note: on, not below).

Outside of the IDE: Your project generates a jar, and you can copy that to Liferay's deploy directory.

Once the module is deployed, it won't magically show up on the page: Log in as Administrator, choose the "Add" button (a plus sign) and add a "widget" to the page: In the list of Widgets you'll find your new portlet/widget.

The screenshot of your installation looks weird though, as if something didn't go wrong and you'll likely need to look for signs of problems in the log file to see why Liferay ends up in the state that it's in, with a couple of default widgets being unavailable - however, that's unrelated to the question how to deploy new code to the runtime.

Edit: You've mentioned the required JDK from the log. That's good to be fixed.

With regards to the not-working drag&drop: It looks like you're using Liferay Workspace. From the icons in Project Explorer, it looks like your module isn't recognized as such: Try to "Gradle/Refresh Gradle Project" (right-click on "modules") to see if it needs some updates that are missing (and observe its log output). Icons on my IDE look like this:

Once you get those modules recognized, you should be able to drag&drop them to the server.

Thanks! I updated the post with a screenshot of drag and drop =) — Megidd, Apr 22 '20 at 15:15
Also updated my post with console log errors: `A full JDK (not just JRE) is required` — Megidd, Apr 22 '20 at 16:08
Sounds like the result to _"you'll likely need to look for signs of problems in the log file"_ — Olaf Kock, Apr 23 '20 at 06:32
Right =) I'm not sure why drag-and-drop is still *not* working for me :( — Megidd, Apr 23 '20 at 07:26
I missed that drag&drop problem earlier. See my edits. Thanks for accepting the answer already. — Olaf Kock, Apr 23 '20 at 08:03