url not showing in references

As others have written, it is not clear how you are using this. Suppose for example you have that bib entry in a file url.bib and then just

\documentclass{article}

\begin{document}
\bibliographystyle{plain}
\nocite{*}
\bibliography{url}
\end{document}

That will give a result similar to the one you got. Maybe this is how you have done it. In that case you should have noticed that there was a warning when you ran Bibtex:

Warning--entry type for "Doe" isn't style-file defined

That is, this default style doesn't know about the @online entry type. (So it shows the normal fields in some normal way, but really doesn't know about that url field.)

The traditional way of entering entries like this in Bibtex is like

@Misc{doemisc,
  author =   {Doe, Ringo},
  title =    {This is a test entry of type {@ONLINE}},
  howpublished = {\url{http://www.test.org/doe/}},
  month =    jun,
  year =     2009}

Use \usepackage{url} in your document to get the \url command.

There may be other Bibtex styles that define an entry type @online but chances are you've seen this because Biblatex has such an entry field. So this LaTeX file using Biblatex can use a bib file with the entry you cited.

\documentclass{article}
\usepackage{biblatex}
\addbibresource{url.bib}

\begin{document}
\nocite{*}
\printbibliography
\end{document}

This easy way worked for me:

Use \bibliographystyle{plainurl} instead of just "plain". This solved everything for me. Enter that command after \bibliography{...}.

Remember to put \usepackage{url}.