Passing messages in method names? Why not!

Have been working with Mockito awesome mocking framework (i LOVE it). It also does use Hamcrest matcher as an option for matching its arguments.

So, say you don't want users of your library to implement interface directly but rather'd like force them to use the Base implementation of this interface and extend it instead? Putting away the reasons which led to this situation, here's how it may be accomplished:

package org.hamcrest;

public interface Matcher extends org.hamcrest.SelfDescribing {

boolean matches(java.lang.Object o);

void _dont_implement_Matcher___instead_extend_BaseMatcher_();

}

Every time you'll try to create a direct implementation of this interface, you'll get this weird method which would tell you what to do.

Good or bad? To me rather bad; something is wrong in design if you offer interface but don't allow users to use it. On the other side it may be good, as BaseMatcher gives some bells and whistles and you don't always know about good base subclass. Also, this may have been caused by some external reasons.

Wicket DownoadLink and AjaxDownload with non-ascii filenames

The problem - yet unsolved for me :(

You have an Apache Wicket application (in my case, this is wicket 1.4.x). You have a page which asks user to download some content and then lets download it. Content is dynamically generated (file?). It should have a name (default one) on client's machine. Name may have cyrillic (or Chinese) symbols.

Symptoms are well described here http://stackoverflow.com/questions/93551/how-to-encode-the-filename-parameter-of-content-disposition-header-in-http

Behavior and the way to overcome it are well described on http://www.codeproject.com/KB/aspnet/NonUSASCII.aspx

Solutions

First of all, I was unable to solve this completely :(

Coming from StackOverflow post, the good way to do would be to form the URL ending with a filename (URL-encoded), and show no filename in Content-Disposition header. All other tricks and tips work not well under different browsers.

Wicket usual approach is to use either DownloadLink or AjaxDownload (thank you guys for such a good solution! Liked it much). First of them is using usual wicket URL coding strategy and second - pretty much the same, being a AjaxBehavior and thus IBehaviorListener. That far I could see no real way to change these URLs. The issue is that both of those don't allow for custom URLs, they are actually plugged into Wicket's infrastructure of page-component-iBehaviorListener-RequestCycle-RequestCodingStrategy chain, so we don't have direct control over it.

One solution proposed by Martin Grigorov on the wicket-users mailing list was to use

http://wicketinaction.com/2011/07/wicket-1-5-mounting-resources/ for mounting, but that did not work out for me as I needed to use containing page's model to generate the actual data.

Fail :(

Will up if any luck.

Wicket this time

another incarnation, switching to wicket-related posting as we're doing wicket jobs at the moment.

Hopefully experiences shared here would save someone's time -- that's a good enough reward.

Java SFTP server review - current state

The life goes on, the new tasks emerge and new research challenges appear.

This time we got the 'heritage' - strangely coupled old system with unclear signal paths (write/poll filesystem instead of doing a local notification call), weird predicates (the file is considered uploaded as soon as 1 hour passes from the start of the upload) and really bad heterohenous design.

The target of the system is get some files uploaded via SFTP (SSH File Transfer Protocol) protocol and process them with some rules, producing output files and making them accessible via the same SFTP. As most of the system is written in Java, we decided to try find the Java SFTP Server to replace part of the existing system. Good things about such an rearchitecturing:

• Making signals simple.
• Having control over filesystem, clients and authentication.
• Introduce uniform build and deploy procedures for the whole system.

A little trouble is that one should distinguish between SFTP and FPTS (FTP over SSL) protocols, as they are completely different.

Having all that in mind, with the good mood we started our little research. Found out some libraries:

• Apache Mina SSHD. Sister project of the Apache FtpServer, this one looks really good in terms of the object design and operation. Code is yet a little fresh, but object breakup is really awesome. We collected our server with the Spring beans and that was pretty easy - to replace the key provider, specify key storage, authenticator and more more other things.
  If you don't want to bother configuring it yourself, the factory gives you pretty good result as it is.
  Being a generic SSH server, Apache SSHD is capable of running SCP and SFTP. Unfortunately, SFTP support is now outdated, and supports only the protocol version 3 (current is 5 or 6). :( We could not use it for the project, as for us it is crucial to have WinSCP support in, and that does not work with protocol v3. After asking about new version guys on the mailing list told me that it'd be awesome if someone implemented that. Who knows if I have some free time, why not? :0
  License is strict GPL
• SshTools is another implementation of the same. Has declared support of the SFTP, SSH and lots of other stuff. Designed pretty good too, has also notion of virtual file system which is very useful if one needs to move storage to DB or process files on the fly. On the other hand, has few documentation and is also licensed under GPL
• JavaSecureFTPd the project is dead as the stone is. GPL, but no one cares :)
• J2SSH Maverick commercial; we did not ever try it, but the rumor says it is pretty good. Has all necessary protocol support.

So, for now situation looks following way - if you have a java app and need to embed SFTP server functionality to it, you either need to try SshTools, help Apache SSHD with the new protocol ;) or pay money for the commercial one.

Not yet sure what we stick to...

Reviving for the second time

Finally, the time has come.
I'm about to change job.
I'm about to change an occupation to something a little different.

Got a new laptop to support my new activities while on the go :) got a new passion and new belief in all the good.

Hopefully will finally establish this blog posting the way i wanted to originally -- one technical posting a week. Think i'll have pretty much of stuff to write on.