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Java Forum / General / December 2007NoClassDefFoundError
I have developed a program with Netbeans for Linux. It accesses a MySQL database. This is done via the com.mysql.jdbc Driver jar file. It works fine when I run the program on its own, but when I try to do it through Java web start, I get a NoClassdefFoundError. Do you know why this can be? The application can be accessed at http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. We run the Tomcat server on Linux. Regards. ... >http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. That JNLP is invalid - the resources element should appear before the application-desc). Here is a valid (and slighly optimized) version of it. <?xml version="1.0" encoding="utf-8"?> <jnlp spec="1.0+" codebase="http://cafka.econ.au.dk/LMDG_Doc/"> <information> <title>Cafkadoc Java Application</title> <vendor>CLS</vendor> <description> Cafka documentation application </description> <description kind="short"> Application for documentation about the DLS projects </description> <offline-allowed/> </information> <security> <all-permissions/> </security> <resources> <j2se version="1.5+"/> <jar href="Mailman.jar"/> </resources> <application-desc /> </jnlp>  SignatureAndrew Thompson http://www.physci.org/ > .. > >http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. [quoted text clipped - 34 lines] > > Message posted via http://www.javakb.com I exchanged it for yours, but I still get the same error. >> .. >> >http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. ... > I exchanged it for yours, but I still get the same error. Did you try flushing the cache (or testing the app. against a new cache - by changing the cache location)? SignatureAndrew Thompson http://www.physci.org/ > >> .. > >> >http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. [quoted text clipped - 5 lines] > > -- How would I do that? I simply have not done that thing. Thank you for helping me. >> >> .. >> >> >http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. >> Did you try flushing the cache (or testing the app. against >> a new cache - by changing the cache location)? > How would I do that? ... I describe it on the end of this thread. <http://forum.java.sun.com/thread.jspa?threadID=5209499> SignatureAndrew Thompson http://www.physci.org/ >... >>http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. >> com.mysql.jdbc .. NoClassdefFoundError > >That JNLP is invalid - the resources element should .. ..also include.. > <resources> > <j2se version="1.5+"/> > <jar href="Mailman.jar"/> > </resources> > <application-desc /> ></jnlp> ..a reference to the Jar that contains the com.mysql.jdbc.* classes, and (checks) Mailman.jar (the only archive referenced in that resources element) surely does *not* contain them! That would be another problem, and probably the underlying cause of the NDFE. SignatureAndrew Thompson http://www.physci.org/ >>... >>>http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. >>> com.mysql.jdbc .. NoClassdefFoundError ... >That would be another problem, and probably the >underlying cause of the NDFE. ummm.. By 'NDFE', I meant the 'NoClassdefFoundError'. SignatureAndrew Thompson http://www.physci.org/ > >>... > >>>http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. [quoted text clipped - 10 lines] > > Message posted via http://www.javakb.com Thanks once more. If you go there, you will see that I have done almost exactly as you indicate in another discussion at http://forum.java.sun.com/thread.jspa?threadID=5240706&tstart=0. I can't follow your tip on cache flush. I use Tomcat on Linux. You stated the Windows case. >> >>... >> >>>http://cafka.econ.au.dk/LMDG_Doc/launchm.jnlp. ... > Thanks once more. If you go there, .. Sorry - where exactly? (Are you referring the the URL to the JNLP file, the other thread at the Sun forums.. somewhere else? >..you will see that I have done almost >exactly as you indicate in another discussion at >http://forum.java.sun.com/thread.jspa?threadID=5240706&tstart=0. I can't >follow your tip on cache flush. I use Tomcat on Linux. You stated the >Windows case. Ummm.. OK. Are you saying that there is *no* *Java* *Control* *Panel* on this *Linux* box? Despite that this page* has screenshots of the JCP on Win., I think it implies the JCP is available (in some form) for all Java installations. * <http://java.sun.com/j2se/1.5.0/docs/guide/deployment/deployment-guide/jcp.html SignatureAndrew Thompson http://www.physci.org/ > Ummm.. OK. Are you saying that there is *no* *Java* *Control* *Panel* > on this *Linux* box? Despite that this page* has screenshots of the > JCP on Win., I think it implies the JCP is available (in some form) > for all Java installations. There typically is a java control panel included in the linux sun jre: "jcontrol", in the jre's /bin directory. (Also called "ControlPanel", but that was a poor name choice on a unix/linux box. Not sure, but I think some/older jres may only have had the "ControlPanel" name. Either way, it's the same tool, just "jcontrol" is a better name) If you want to use the linux java control panel on a GUI-less server, path of least pain is probably to just "ssh -X" (i.e. forward the X11 connection) into the server from a linux (or other X11) desktop with a GUI. > I have developed a program with Netbeans for Linux. It accesses a MySQL > database. This is done via the com.mysql.jdbc Driver jar file. It works [quoted text clipped - 4 lines] > on > Linux. I saw the JNLP posted by Andrew Thompson. The answer is simple, you need to add the mysql driver jar file to the jnlp under the resources section and also have the jar file on the server. For example, I keep my jars in the relative directory lib/ and include the following line in my jnlp (you might have a different driver name so substitute yours): <jar href="lib/mysql-connector-java-5.0.3-bin.jar" download="lazy"/> Cheers Lionel. >NoClassdefFoundError see http://mindprod.com/jgloss/runerrormessages.html#NOCLASSDEFFOUNDERROR This is the hardest exception to track down. It has many many possible causes. I wish Sun could figure out some way to break it down into subexceptions. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >> NoClassdefFoundError > [quoted text clipped - 4 lines] > causes. I wish Sun could figure out some way to break it down into > subexceptions. But a rather obvious starting point in this case is to include the driver file which contains the classes that the OP is actually trying to load dynamically! >>> NoClassdefFoundError ... >> causes. I wish Sun could figure out some way to break it down into >> subexceptions. > >But a rather obvious starting point in this case is to include the >driver file which contains the classes that the OP is actually trying to >load dynamically! Sure. But two people have now identified that aspect (not that Roedy would necessarily have noticed) and Roedy tends to take the 'high overview' and replies with 'a wealth of information to cover the possibilities' that is encapsulated in the page at the end of the link provided. Added to that, it is a hint to the OP that most compile/run-time errors can be explored/investigated at the mindpord site. So the *next* time the OP sees a NoClassdefFoundError, or an AccessControlException, or an.. (etc) they know a good place to start, in investigating it. SignatureAndrew Thompson http://www.physci.org/ >Added to that, it is a hint to the OP that most compile/run-time >errors can be explored/investigated at the mindpord site. So >the *next* time the OP sees a NoClassdefFoundError, or an >AccessControlException, or an.. (etc) they know a good >place to start, in investigating it. As Andrew usually puts it "this is not a help desk". In my view you generally should NOT hand the solution on a plate. You should give general information useful to solve that class of problems. In the process of applying those hints, the questioner becomes a better programmer. There is a matter of balance. If you give too general a hint, the student becomes discouraged and gets the idea he/she is hopeless. If you give too specific a hint, they don't learn anything. Just right, and the student gets a great rush of accomplishment, (which reinforces learning), and learns the most about that class of problem. If the questioner is an accomplished Java programmer, simply handing over the answer is appropriate. They have probably already tried the usual mechanisms and for some reason went off on some wrong tangent in understanding. The other way I look at this is, the questioner is NOT the primary intended audience. It is all the other students. The other students are not interested in the minutiae of the problem. They want to learn something they can apply to THEIR problems. So you should try to give advice that is generally applicable. What I am often doing when I come in late to the conversation is pointing out the student could have handled this on his own simply by looking up a few keywords in the Java glossary. Then there is no delay waiting for an answer that may never come, or may come with a large dose of invective. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com >>Added to that, it is a hint to the OP that most compile/run-time >>errors can be explored/investigated at the mindpord site. So >>the *next* time the OP sees a NoClassdefFoundError, or an >>AccessControlException, or an.. (etc) they know a good >>place to start, in investigating it. ... >There is a matter of balance. ... Thank you for that quote. It is ..nice to hear you express something that sounds surprising* (to me). * Your goodwill and good intention is not a question (worthy of the slightest thought). SignatureAndrew Thompson http://www.physci.org/ ... >The other way I look at this is, the questioner is NOT the primary >intended audience. It is all the other students. The other students >are not interested in the minutiae of the problem. They want to learn >something they can apply to THEIR problems. So you should try to give >advice that is generally applicable. F'cken Yay. (sorry - did not mean to interrupt this sound exposition, but I was ..'possessed by a great spirit' (shrugs vaguely - that'll do)). >What I am often doing when I come in late to the conversation is >pointing out the student could have handled this on his own simply by >looking up a few keywords in the Java glossary. Then there is no >delay waiting for an answer that may never come, or may come with a >large dose of invective. Well stated. SignatureAndrew Thompson http://www.physci.org/ >... >What I am often doing when I come in late to the conversation is [quoted text clipped - 4 lines] > >Well stated. In fact, to take that (a little) further, my 'homepage' at the moment is a simple page on my local file-system that has 'handy links' as well as a 'search form' pointed at Google, that can specify - search string - file type, & - domain search For the file type and domain search, I have drop down lists. The domain search includes 8 Java related domains - *one of those 8* is mindprod. The mindprod site rates highly in my 'search for knowledge' in relation to the Java programming language. SignatureAndrew Thompson http://www.physci.org/ ... >..'search form' pointed at Google, Speaking of which. Drop this in some HTML. Very handy (if I say so myself). <form method='get' action='http://www.google.com/search'> Text: <input type='text' size='20' name='as_q'> Filetype: <select name='as_filetype' size='1'> <option value='' selected>All <option value='java'>Java <option value='jnlp'>JNLP <option value='hs'>HelpSet <option value='au'>Sound - AU <option value='wav'>Sound - Wav <option value='aiff'>Sound - AIFF <option value='jpg'>Image - JPEG <option value='gif'>Image - GIF <option value='png'>Image - PNG </select> Site: <select name='as_sitesearch' size='1'> <option value='' selected>All <option value='java.sun.com'>Sun <option value='forum.java.sun.com'>Sun - Forums <option value='bugs.sun.com'>Sun - Bug DB <option value='ant.apache'>Apache - Ant <option value='mindprod.com'>Mindprod <option value='physci.org'>PhySci <option value='java.net'>Java.net <option value='dev.java.net'>Java.net - Dev </select> <input type='submit'> </form> HTH SignatureAndrew Thompson http://www.physci.org/ > But a rather obvious starting point in this case is to include the > driver file which contains the classes that the OP is actually trying to > load dynamically! Thanks a lot for giving straight advice. Your solution worked, but there was one more thing that I had to do for the error not to come. The jar of the SQL database driver had to be signed as well. I thought that it was enough to include it. It was downloaded from an official source. The documentation on this is not very clear, neither from Apache or Netbeans or the stuff on JNLP files from Sun. That's why I needed some help from here. Regards, Håkan Lane > The documentation on this is not very clear, neither from Apache or > Netbeans or the stuff on JNLP files from Sun. That's why I needed some > help from here. I have to beg the differ on that one. The documentation for JWS does clearly state that you must sign your jars. You need to work closely with the Java control panel to get all the debugging output to see what is going on. But glad you got there. Lionel. ... > ...The >jar of the SQL database driver had to be signed as well. Does it? I had been meaing to ask why your project specified <all-permissions/>. That is not necessary for an app. that simply wants to 'phone home' to a DB coming off the same server. If you need the app. to contact a different server, then it would require either trust or the user to OK the cross-domain access. What else does the project do that might require trust? Have you tried it without asking for all-permissions? SignatureAndrew Thompson http://www.physci.org/ >The >jar of the SQL database driver had to be signed as well. If you are asking how to sign jars, see http://mindprod.com/jgloss/jarsignerexe.html http://mindprod.com/jgloss/jar.html http://mindprod.com/jgloss/certificate.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com On Sun, 02 Dec 2007 20:27:09 +0100, "H.L" <H.L@softhome.net> wrote, quoted or indirectly quoted someone who said : >The >jar of the SQL database driver had to be signed as well. If you are asking how to sign jars, see http://mindprod.com/jgloss/jarsignerexe.html http://mindprod.com/jgloss/jar.html http://mindprod.com/jgloss/certificate.html SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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