It is possible to view Javadoc hovers with eclipse.jdt.ls?

[francesco-cadei]

I have installed eglot and setted up with eclipse.jdt.ls .
All works fine but it would be amazing if there was the possibility to view Javadoc hovers like promised by eclipse.jdt.ls.

[yveszoundi]

@francesco-cadei , I think that the notion of "hover" in eglot means at the current "cursor location" (i.e., not mouse hover).
I don't know if that was also your current understanding or expectation (eldoc).

I've noticed that few "weird" JDT.LS things in respect to javadoc information:

• For basic JDK types, you can usually get javadoc information on methods (getName, but not non classes (java.io.File)
• For external libraries, it seems that the javadoc information is looked up properly with the cursor either on a method, class or package/module
• There might be other discrepancies, in comparison to what you see in a full blown IDE: I usually write code without IDE or LSP myself

In the screenshot below, the mouse cursor is on assertThat (JUnit method), and the javadoc is displayed inside the eldoc buffer (M-x eldoc-doc-buffer).

[francesco-cadei]

Thanks for the answer.
It is possible to have a little description of the methods like oracle https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/io/PrintStream.html#println()?

[yveszoundi]

Yes, per screenshot below with the specific example in your follow-up question.

• Does it not work when you try it, with the mouse cursor on println and the eldoc buffer open? (M-x eldoc-doc-buffer)?
• You might also need the package markdown-mode installed too, for rendering the javadocs (I can't recall).

[francesco-cadei]

I have the markdown-mode. But for the println() I only have this:

my settings of eglot:

(use-package eglot
  :config
  (add-to-list 'eglot-server-programs
	       '(java-mode . ("~/jdt-language-server-1.33.0-202402151717/bin/jdtls")))
  :hook
  (java-mode . eglot-ensure) ;; https://download.eclipse.org/jdtls/milestones/?d
  (js-mode . eglot-ensure) ;; npm install -g typescript-language-server typescript
  )

[yveszoundi]

I think that you also need to install JDK sources depending on your environment (openjdk-21-source on Ubuntu, essentially having src.zip in $JAVA_HOME/jre/lib accordingly to your JDK version).

[francesco-cadei]

I am in debian and I was using default-jdk.
Now solved with openjdk-17-jdk and openjdk-17-source.