Thanks all for your interest, especially Uwe. I asked this question on solr-user at the beginning but I got no reply. That's why I re-asked the question at java-user. Thanks for your efforts. I will try it now.
On Mon, Dec 28, 2009 at 12:02 PM, Uwe Schindler <u...@thetaphi.de> wrote: > I opened https://issues.apache.org/jira/browse/LUCENE-2182 about this > problem and already have a fix. > > This is really a bug. The solution is simple because you have to load the > IMPL class using the same classloader as the passed in interface. The > default for Class.forName is the classloader of AttributeSource.class, > which > is the wrong one. > > ----- > Uwe Schindler > H.-H.-Meier-Allee 63, D-28213 Bremen > http://www.thetaphi.de > eMail: u...@thetaphi.de > > > -----Original Message----- > > From: Uwe Schindler [mailto:u...@thetaphi.de] > > Sent: Monday, December 28, 2009 9:20 AM > > To: java-u...@lucene.apache.org > > Cc: solr-user@lucene.apache.org > > Subject: RE: Using the new tokenizer API from a jar file > > > > The question on this list was ok,as it shows a minor problem of using the > > new TokenStream API with Solr. > > > > His plugin was loaded correctly, because if Lucene says, that it cannot > > find > > the *Impl class, it was able to load the interface class before -> the > JAR > > file is "visible" to the JVM. > > > > The problem is the following and has to do with classloaders: > > > > 1. We have different class loaders for different places in Solr. Solr > uses > > for plugins a SolrResourceLoader that searches for JAR files in the local > > lib folder before handling over to the webapp's classloader. > > > > 2. Initially, the lucene JAR is loaded by the Webapp's class loader > > > > 3. If a AttributeImpl is placed into a jar file e.g. in the plugin folder > > of > > solr (the lib folder where solr loads all resources, stop words,...), the > > loading mechanism inside AttributeSource.DEFAULT_ATTRIBUTE_FACTORY is > > unable > > to locate the class file, because Class.forName() always uses the class' > > classloader and not the global/thread one's. So AttributeSource will only > > find the class file if it is in the *same* directory as the lucene- > > core.jar > > file (WEB-INF/lib) and so accessible by the webapp's class loader. > > > > A good introduction about the problem is this one: > > > http://www.theserverside.com/tt/articles/content/dm_classForname/DynLoad.p > > df > > > > The problem is here described for the JVM extensions folder but also > > applies > > to solr, because it has another classloader for plugins. > > > > A solution to fix this would be in lucene to use the thread's context > > class > > loader in AttributeSource.DEFAULT_ATTRIBUTE_FACTORY, but I strongly > > discourage this, as it would break the whole AttributeSource > functionality > > if you add two different attributes with same class names from different > > class loaders to the AttributeSource. > > > > The only solution to the problem is placing the JAR file inside the > > WEB-INF/lib folder where lucene-core.jar is. Plugins in Solr cannot > define > > own attribute implementations. Alternatively he could try to force > preload > > the class by calling Class.forName in his plugin initialization code on > > the > > Impl class. But I am not sure if this works (as Java handles classes from > > different classloaders different). > > > > Uwe > > > > ----- > > Uwe Schindler > > H.-H.-Meier-Allee 63, D-28213 Bremen > > http://www.thetaphi.de > > eMail: u...@thetaphi.de > > > > > -----Original Message----- > > > From: Chris Hostetter [mailto:hossman_luc...@fucit.org] > > > Sent: Monday, December 28, 2009 4:27 AM > > > To: java-u...@lucene.apache.org > > > Subject: Re: Using the new tokenizer API from a jar file > > > > > > > > > : I tried to use it with solr and the problems began. It's always > > telling > > > me > > > : that it cannot find the class GlossAttributeImpl. I think the problem > > is > > > : that my jar file is added to the class path at run time not from the > > > command > > > : line. Do you have a good solution or workaround? > > > > > > You're likely to get mmore helpful answers from other people in the > Solr > > > User community (solr-u...@lucene.a.o) > > > > > > As long as you put your jar in the "lib" directory under your solr home > > > (or refrence it using a <lib/> directive in your solrconfig.xml) Solr's > > > plugin loader will take care of hte classloading for you. > > > > > > if you are confident you have your jar in the correct place, please > > email > > > solr-user with the ClassNotFound stack trace from your solr logs, as > > well > > > as hierarchy of files from your solr home (ie: the output of "find .") > > > > > > > > > -Hoss > > > > > > > > > --------------------------------------------------------------------- > > > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > > > For additional commands, e-mail: java-user-h...@lucene.apache.org > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > > For additional commands, e-mail: java-user-h...@lucene.apache.org > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > For additional commands, e-mail: java-user-h...@lucene.apache.org > > -- regards, Ahmed Saad
