documents: libreoffice not working; could not find a JRE

[patte]

I saw that in installNextcloud.sh you pacman libreoffice-fresh, so I followed that the setup should had full libreoffice support.
Problem is, when I try to enable M$ Word Support (in Admin -> Settings -> Documents -> Local) I get the Error Conversion failed. Check log for details. In the log I find the following line:

{"reqId":"REMOVED","remoteAddr":"REMOVED","app":"documents","message":"Conversion test failed. Raw output:javaldx: Could not find a Java Runtime Environment!\nWarning: failed to read path from javaldx\n","level":2,"time":"2016-08-28T14:56:03+00:00","method":"POST","url":"\/index.php\/apps\/documents\/ajax\/admin.php","user":"admin"}

I exec bashed into the container and tried to run libreoffice manually, there I discovered the could not find a JRE.

[root@be2dcffd103d /]# li
libassuan-config  libmcrypt-config  libpng16-config   libtool           link              linux32
libgcrypt-config  libpng-config     libreoffice       libtoolize        linkicc           linux64
[root@be2dcffd103d /]# libreoffice -v
Failed to open display
javaldx: Could not find a Java Runtime Environment!
Warning: failed to read path from javaldx
terminate called after throwing an instance of 'com::sun::star::uno::DeploymentException'
[root@be2dcffd103d /]# libreoffice --version
terminate called after throwing an instance of 'com::sun::star::uno::DeploymentException'
[root@be2dcffd103d /]# java -version
bash: java: command not found
[root@be2dcffd103d /]#

And ideas what I might get wrong?