RE: Tomcat 6.0 documentation: is classloading description correct?
Caldarale, Charles R chuck.caldar...@unisys.com wrote on 06/16/2010 09:55:19 PM: From: peter_f...@blm.gov [mailto:peter_f...@blm.gov] Subject: Re: Tomcat 6.0 documentation: is classloading description correct? The docs say in one place that the order is one way (WebApp first, then Boot, System and Common, which is as I'd expect) Please document where it says that; make sure not to ignore the sentence: There are exceptions. Also, don't assume that the complete list of exceptions is described in that paragraph rather than the bulleted list. The exceptions it gives are the ones I'd expect - no overriding JRE classes, servlet classes ignored, use of the endorsed override mechanism. I'm really more interested in the non-exceptional case of simply loading my application classes and those from third-party jars such as Apache Commons packages. I need confirmation that that second part of the documentation is in error (or not, of course). All parts of the classloader doc appear to be correct to me, also confirmed by a quick glance at the code. I don't see how that can be the case: When a request to load a class from the web application's WebappX class loader is processed, this class loader will look in the local repositories first, instead of delegating before looking ... All other class loaders in Tomcat 6 follow the usual delegation pattern. But then it says, this, which describes a different search order: Bootstrap classes of your JVM System class loader classes (described above) /WEB-INF/classes of your web application /WEB-INF/lib/*.jar of your web application $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar They can't *both* be right. --Pete You might want to look at the API spec for the class of interest: http://tomcat.apache.org/tomcat-6.0- doc/api/org/apache/catalina/loader/WebappClassLoader.html - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Tomcat 6.0 documentation: is classloading description correct?
2010/6/16 peter_f...@blm.gov: Looking at section 10 of the 6.0 user guide, which describes classloading, the text makes perfect sense and matches the way I understand things work. However the summary at the end of the section Class Loader Definitions looks wrong; it basically says that the search order is... Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar ...when my understanding is it should be... WEB-INF/classes WEB-INF/lib/*.jar Bootstrap $CLASSPATH $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar So, is the documentation just wrong, or have I misunderstood something? The order is Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_BASE/lib $CATALINA_BASE/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar as documented. Note, that many Bootstrap and $CLASSPATH classes are loaded at early stages of Tomcat startup sequence, that is before classloading hierarchy itself is created. It would be a mess if those classes were ignored. That is why people should not play with $CLASSPATH, unless in certain very rare cases. If you have some documentation changes in your mind, the patches are welcome. The sources are in webapps/docs/*.xml . Create a Bugzilla issue and attach a diff file there (svn diff or an 'Unified diff' (diff -u)). Best regards, Konstantin Kolinko - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Tomcat 6.0 documentation: is classloading description correct?
On 17.06.2010 16:37, Konstantin Kolinko wrote: 2010/6/16peter_f...@blm.gov: Looking at section 10 of the 6.0 user guide, which describes classloading, the text makes perfect sense and matches the way I understand things work. However the summary at the end of the section Class Loader Definitions looks wrong; it basically says that the search order is... Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar ...when my understanding is it should be... WEB-INF/classes WEB-INF/lib/*.jar Bootstrap $CLASSPATH $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar So, is the documentation just wrong, or have I misunderstood something? The order is Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_BASE/lib $CATALINA_BASE/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar as documented. Note, that many Bootstrap and $CLASSPATH classes are loaded at early stages of Tomcat startup sequence, that is before classloading hierarchy itself is created. It would be a mess if those classes were ignored. That is why people should not play with $CLASSPATH, unless in certain very rare cases. If you have some documentation changes in your mind, the patches are welcome. The sources are in webapps/docs/*.xml . Create a Bugzilla issue and attach a diff file there (svn diff or an 'Unified diff' (diff -u)). I guess part of the confusion comes from the terminology parent and delegating. The classloader used by the webapps is derived from the usual URLClassloader as an extension. In Tomcat land it's parent is the classloader that loads from the common lib directory. The webapp classloader is not delegating first in the sense that it first tries to find classes via it's own super URLClassloader, before asking the parent common loader. The URLClassloader in turn is the one, that first goes down to bootstrap and system/CLASSPATH before checking the configured URLs (WEB-INF). So in Tomcat terminology it's true, that the webapp classloader does only delegate (to common) if it can't find the class, but the webapp loader itself does delegate to bootstrap and system first. (hope that's true and not too confusing ...) Regards, Rainer - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Tomcat 6.0 documentation: is classloading description correct?
Ok, the problem is my misunderstanding of the process here. I thought WebAppClassLoader always checked WEB-INF/lib before delegating; I see that it actually delegates to the System loader first, then checks WEB-INF/lib, and finally delegates to its own parent. So my comment earlier about they can't both be right was of course wrong - not only *can* they be both right, they *are* :) This explains the technical problem I've been chasing; I'll have it fixed in a jiffy now. Thanks all. --Pete Konstantin Kolinko knst.koli...@gmail.com wrote on 06/17/2010 08:37:56 AM: 2010/6/16 peter_f...@blm.gov: Looking at section 10 of the 6.0 user guide, which describes classloading, the text makes perfect sense and matches the way I understand things work. However the summary at the end of the section Class Loader Definitions looks wrong; it basically says that the search order is... Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar ...when my understanding is it should be... WEB-INF/classes WEB-INF/lib/*.jar Bootstrap $CLASSPATH $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar So, is the documentation just wrong, or have I misunderstood something? The order is Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_BASE/lib $CATALINA_BASE/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar as documented. Note, that many Bootstrap and $CLASSPATH classes are loaded at early stages of Tomcat startup sequence, that is before classloading hierarchy itself is created. It would be a mess if those classes were ignored. That is why people should not play with $CLASSPATH, unless in certain very rare cases. If you have some documentation changes in your mind, the patches are welcome. The sources are in webapps/docs/*.xml . Create a Bugzilla issue and attach a diff file there (svn diff or an 'Unified diff' (diff -u)). Best regards, Konstantin Kolinko - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Tomcat 6.0 documentation: is classloading description correct?
Use Class Loader Definitions carefully, System - This class loader is normally initialized from the contents of the CLASSPATH environment variable. All such classes are visible to both Tomcat internal classes, and to web applications. However, the standard Tomcat 6 startup scripts ($CATALINA_HOME/bin/catalina.sh or %CATALINA_HOME%\bin\catalina.bat) totally ignore the contents of the CLASSPATH environment variable itself, and instead build the System class loader from the following repositories: I think that documentation is correct, --Gurkan From: peter_f...@blm.gov peter_f...@blm.gov To: users@tomcat.apache.org Sent: Wed, June 16, 2010 9:42:35 PM Subject: Tomcat 6.0 documentation: is classloading description correct? Looking at section 10 of the 6.0 user guide, which describes classloading, the text makes perfect sense and matches the way I understand things work. However the summary at the end of the section Class Loader Definitions looks wrong; it basically says that the search order is... Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar ...when my understanding is it should be... WEB-INF/classes WEB-INF/lib/*.jar Bootstrap $CLASSPATH $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar So, is the documentation just wrong, or have I misunderstood something? - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Tomcat 6.0 documentation: is classloading description correct?
When I wrote CLASSPATH I meant the classpath value that's built up by the catalina.sh - I'm well aware that it creates this from clean. I think you're missing the point; CLASSPATH is used to set the System classloader's search path, sure - but the question is where that loader fits into the loader search order used by Tomcat. The docs say in one place that the order is one way (WebApp first, then Boot, System and Common, which is as I'd expect) but in another place right after that says that it's Boot, System, WebApp, Common (which I think is wrong). I need confirmation that that second part of the documentation is in error (or not, of course). Gurkan Erdogdu gurkanerdo...@yahoo.com wrote on 06/16/2010 03:04:08 PM: Use Class Loader Definitions carefully, System - This class loader is normally initialized from the contents of the CLASSPATH environment variable. All such classes are visible to both Tomcat internal classes, and to web applications. However, the standard Tomcat 6 startup scripts ($CATALINA_HOME/bin/catalina.sh or %CATALINA_HOME%\bin\catalina.bat) totally ignore the contents of the CLASSPATH environment variable itself, and instead build the System class loader from the following repositories: I think that documentation is correct, --Gurkan From: peter_f...@blm.gov peter_f...@blm.gov To: users@tomcat.apache.org Sent: Wed, June 16, 2010 9:42:35 PM Subject: Tomcat 6.0 documentation: is classloading description correct? Looking at section 10 of the 6.0 user guide, which describes classloading, the text makes perfect sense and matches the way I understand things work. However the summary at the end of the section Class Loader Definitions looks wrong; it basically says that the search order is... Bootstrap $CLASSPATH WEB-INF/classes WEB-INF/lib/*.jar $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar ...when my understanding is it should be... WEB-INF/classes WEB-INF/lib/*.jar Bootstrap $CLASSPATH $CATALINA_HOME/lib $CATALINA_HOME/lib/*.jar So, is the documentation just wrong, or have I misunderstood something? - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
RE: Tomcat 6.0 documentation: is classloading description correct?
From: peter_f...@blm.gov [mailto:peter_f...@blm.gov] Subject: Re: Tomcat 6.0 documentation: is classloading description correct? The docs say in one place that the order is one way (WebApp first, then Boot, System and Common, which is as I'd expect) Please document where it says that; make sure not to ignore the sentence: There are exceptions. Also, don't assume that the complete list of exceptions is described in that paragraph rather than the bulleted list. I need confirmation that that second part of the documentation is in error (or not, of course). All parts of the classloader doc appear to be correct to me, also confirmed by a quick glance at the code. You might want to look at the API spec for the class of interest: http://tomcat.apache.org/tomcat-6.0-doc/api/org/apache/catalina/loader/WebappClassLoader.html - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
