Javadoc is not displayed when calling CocAction('doHover')

I am using OpenJDK 11 on Debian and have the corresponding doc package installed. Previously, I was getting javadoc info from the OpenJDK doc package when calling CocAction(‘doHover’). Now when I call CocAction('doHover') (using a keymapping or the command prompt) with the cursor on a keyword like String, I do not get the javadoc info from the doc package in the preview window like I did before. Instead I get this:

This is the information I was seeing before I installed the doc package.

I don’t know if it’s related, but I started having this problem after I applied the fix for #15. Before that, I was getting the correct documentation.

I updated the server from jdt-language-server-0.36.0-201903201910 to jdt-language-server-0.36.1-201904020132 by running :CocCommand java.updateLanguageServer to see if that would fix the issue, but it did not.

This is the trace I get when i try to get the hover info:

[Trace - 3:45:08 PM] Sending request 'textDocument/hover - (5)'.
Params: {
    "textDocument": {
        "uri": "file:///home/user/udemy/maven/mb2g-lombok/src/main/java/guru/springframework/model/User.java"
    },
    "position": {
        "line": 12,
        "character": 14
    }
}


[Trace - 3:45:08 PM] Received response 'textDocument/hover - (5)' in 56ms.
Result: {
    "contents": {
        "language": "java",
        "value": "java.lang.String"
    }
}

[ioperations]

solved by

 sudo apt install openjdk-${VERSION}-source 

[rajitbanerjee]

I had a similar issue with no hover showing at all until I added this to my vimrc:

function! ShowDocIfNoDiagnostic(timer_id)
  if (coc#float#has_float() == 0 && CocHasProvider('hover') == 1)
    silent call CocActionAsync('doHover')
  endif
endfunction

function! s:show_hover_doc()
  call timer_start(500, 'ShowDocIfNoDiagnostic')
endfunction

autocmd CursorHoldI * :call <SID>show_hover_doc()
autocmd CursorHold * :call <SID>show_hover_doc()

Thanks to https://thoughtbot.com/blog/modern-typescript-and-react-development-in-vim#tool-tip-documentation-and-diagnostics