NoSuchMethodError loading class in webapp from common class loader
Hi, I am running Tomcat 7.0.28 on RHEL 6.2 with a single web app. The web app in question uses reflection to load some implementations of our classes (kind of like a service loader) knowing the class name. I am trying to add additional implementations by dropping them in the tomcat's lib directory but I keep seeing NoSuchMethodError for the constructor to the class. I know the constructor is there because if I move the jar into the web app's lib directory (webapp/[WEB_APP]/WEB_INF/lib) everything works. I figure this must be some class loader issue I am not understanding but these docs[1][2] don't seem to indicate there should be any issue. -Bryan [1] - http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html [2] - http://download.oracle.com/otndocs/jcp/servlet-2.4-fr-spec-oth-JSpec/
Re: NoSuchMethodError loading class in webapp from common class loader
2013/5/3 Bryan Baugher bjb...@gmail.com: Hi, I am running Tomcat 7.0.28 on RHEL 6.2 with a single web app. The web app in question uses reflection to load some implementations of our classes (kind of like a service loader) knowing the class name. I am trying to add additional implementations by dropping them in the tomcat's lib directory but I keep seeing NoSuchMethodError for the constructor to the class. I know the constructor is there because if I move the jar into the web app's lib directory (webapp/[WEB_APP]/WEB_INF/lib) everything works. I figure this must be some class loader issue I am not understanding but these docs[1][2] don't seem to indicate there should be any issue. -Bryan [1] - http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html [2] - http://download.oracle.com/otndocs/jcp/servlet-2.4-fr-spec-oth-JSpec/ Using the common classloader is somewhat tricky, because the Webapp classloader has priority rule imposed by servlet spec does mess up things, as explained in [1]. Your description does not have enough details, nor source code, nor stacktaces, and with such I would guess that you have the following: a) Your constructor has some arguments b) The classes mentioned as argument types in that method can be loaded both from common class loader and from webapp classloader. (If they cannot be loaded from the former, you are also in trouble). c) Classes loaded from different classloaders are considered different by JVM (even if they have the same name and bytecode),. You are asking for a method specifying its arguments by using classes loaded by webapp classloader and they do not match the ones loaded by common classloader Just a guess. Best regards, Konstantin Kolinko - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: NoSuchMethodError loading class in webapp from common class loader
Sorry I tried to leave on what I thought were unnecessary details. You are correct my constructor has arguments. One of the arguments comes from another dependency jar that exists in both the webapp and tomcat/lib so I think your guess (c) could be right. I guess the solution would be to move the dependency out of the webapp and into tomcat/lib. On Fri, May 3, 2013 at 9:16 AM, Konstantin Kolinko knst.koli...@gmail.comwrote: 2013/5/3 Bryan Baugher bjb...@gmail.com: Hi, I am running Tomcat 7.0.28 on RHEL 6.2 with a single web app. The web app in question uses reflection to load some implementations of our classes (kind of like a service loader) knowing the class name. I am trying to add additional implementations by dropping them in the tomcat's lib directory but I keep seeing NoSuchMethodError for the constructor to the class. I know the constructor is there because if I move the jar into the web app's lib directory (webapp/[WEB_APP]/WEB_INF/lib) everything works. I figure this must be some class loader issue I am not understanding but these docs[1][2] don't seem to indicate there should be any issue. -Bryan [1] - http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html [2] - http://download.oracle.com/otndocs/jcp/servlet-2.4-fr-spec-oth-JSpec/ Using the common classloader is somewhat tricky, because the Webapp classloader has priority rule imposed by servlet spec does mess up things, as explained in [1]. Your description does not have enough details, nor source code, nor stacktaces, and with such I would guess that you have the following: a) Your constructor has some arguments b) The classes mentioned as argument types in that method can be loaded both from common class loader and from webapp classloader. (If they cannot be loaded from the former, you are also in trouble). c) Classes loaded from different classloaders are considered different by JVM (even if they have the same name and bytecode),. You are asking for a method specifying its arguments by using classes loaded by webapp classloader and they do not match the ones loaded by common classloader Just a guess. Best regards, Konstantin Kolinko - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org -- -Bryan
RE: NoSuchMethodError loading class in webapp from common class loader
From: Bryan Baugher [mailto:bjb...@gmail.com] Subject: Re: NoSuchMethodError loading class in webapp from common class loader One of the arguments comes from another dependency jar that exists in both the webapp and tomcat/lib Never, never, never put the same class in the webapp and tomcat/lib - that is a guarantee of nasty class resolution failures. - 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
Re: NoSuchMethodError loading class in webapp from common class loader
I was able to verify that you are correct the JVM treats those classes as different which is why I was getting NoSuchMethodError. After experimenting some more this method seems to be the wrong approach. Do you know of any better approaches on how to add runtime dependencies to a webapp? On Fri, May 3, 2013 at 9:45 AM, Bryan Baugher bjb...@gmail.com wrote: Sorry I tried to leave on what I thought were unnecessary details. You are correct my constructor has arguments. One of the arguments comes from another dependency jar that exists in both the webapp and tomcat/lib so I think your guess (c) could be right. I guess the solution would be to move the dependency out of the webapp and into tomcat/lib. On Fri, May 3, 2013 at 9:16 AM, Konstantin Kolinko knst.koli...@gmail.com wrote: 2013/5/3 Bryan Baugher bjb...@gmail.com: Hi, I am running Tomcat 7.0.28 on RHEL 6.2 with a single web app. The web app in question uses reflection to load some implementations of our classes (kind of like a service loader) knowing the class name. I am trying to add additional implementations by dropping them in the tomcat's lib directory but I keep seeing NoSuchMethodError for the constructor to the class. I know the constructor is there because if I move the jar into the web app's lib directory (webapp/[WEB_APP]/WEB_INF/lib) everything works. I figure this must be some class loader issue I am not understanding but these docs[1][2] don't seem to indicate there should be any issue. -Bryan [1] - http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html [2] - http://download.oracle.com/otndocs/jcp/servlet-2.4-fr-spec-oth-JSpec/ Using the common classloader is somewhat tricky, because the Webapp classloader has priority rule imposed by servlet spec does mess up things, as explained in [1]. Your description does not have enough details, nor source code, nor stacktaces, and with such I would guess that you have the following: a) Your constructor has some arguments b) The classes mentioned as argument types in that method can be loaded both from common class loader and from webapp classloader. (If they cannot be loaded from the former, you are also in trouble). c) Classes loaded from different classloaders are considered different by JVM (even if they have the same name and bytecode),. You are asking for a method specifying its arguments by using classes loaded by webapp classloader and they do not match the ones loaded by common classloader Just a guess. Best regards, Konstantin Kolinko - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org -- -Bryan -- -Bryan
RE: NoSuchMethodError loading class in webapp from common class loader
-Original Message- From: Bryan Baugher [mailto:bjb...@gmail.com] Sent: Friday, May 03, 2013 6:52 AM To: users@tomcat.apache.org Subject: NoSuchMethodError loading class in webapp from common class loader Hi, I am running Tomcat 7.0.28 on RHEL 6.2 with a single web app. The web app in question uses reflection to load some implementations of our classes (kind of like a service loader) knowing the class name. I am trying to add additional implementations by dropping them in the tomcat's lib directory but I keep seeing NoSuchMethodError for the constructor to the class. I know the constructor is there because if I move the jar into the web app's lib directory (webapp/[WEB_APP]/WEB_INF/lib) everything works. I figure this must be some class loader issue I am not understanding but these docs[1][2] don't seem to indicate there should be any issue. -Bryan [1] - http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html [2] - http://download.oracle.com/otndocs/jcp/servlet-2.4-fr-spec-oth- JSpec/ Not to say this affects your specific problem, but I see you referencing the Servlet 2.4 Specification. Tomcat 7 is based on Servlet Specification v3.0: http://jcp.org/en/jsr/detail?id=315 Regards, Denise - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
RE: NoSuchMethodError loading class in webapp from common class loader
From: Denise K. Erwin [mailto:dkerwi...@gmail.com] Subject: RE: NoSuchMethodError loading class in webapp from common class loader Not to say this affects your specific problem, but I see you referencing the Servlet 2.4 Specification. Tomcat 7 is based on Servlet Specification v3.0: Which is compatible with 2.4, 2.5, etc., so it's not an issue. - 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
