Re: Accessing static variable from different webapps
Thanks a lot for helping me understand all this concepts about classloading. I found a pretty good article on class loading in java. http://www.onjava.com/pub/a/onjava/2005/01/26/classloading.html Thanks, Anshaj On Thu, 03 Feb 2005 22:25:53 +0100, Mario Winterer [EMAIL PROTECTED] wrote: For more information on tomcat's classloading concept have a look at: http://jakarta.apache.org/tomcat/tomcat-5.5-doc/class-loader-howto.html As you can see there, Tomcat instantiates a classloader for each web application. So if you put a class - let's say Global - inside the WEB-INF/classes directory of each of two of your web applications, it will be loaded twice. As a fact, a static variable of the Global class - let's say Global.myVar - will exist twice too! But if you put your Global class into the %TOMCAT_HOME%/shared/classes directory ONLY (important: you must remove all occurences of your Global class from the webapps-classes directories to make this work!), it will be loaded by the shared-classloader. Because of the fact that the shared classloader is the parent classloader of all webapp-classloaders, every web-application can access the classes loaded by the shared classloader. But holding resources in static variables inside the shared/classes directory there is not recommmended! Better add a JNDI-resource to your Tomcat's JNDI-context! This is done in server.xml inside the GlobalNamingResources-element* *(see http://jakarta.apache.org/tomcat/tomcat-5.5-doc/config/globalresources.html). Best regards, Tex Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. Thanks, Anshaj On Thu, 03 Feb 2005 06:41:29 -0500, Tim Funk [EMAIL PROTECTED] wrote: Put the class in the common or shared classloader. -Tim Anshaj Mathur wrote: Dear group, I have public class which contains a static variable type integer. I am running different webapps inside single instance of tomcat. I initiated this class in different webapps. I increased the count from a webapp and tried to see it from different webapp. I found that count was not increased in other webapp. It was showing the original count. Am I braking any laws of tomcat security. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- v1.2a r TW 0/0/ FD + 0 DSotM 3 100 21.3% 3jan5 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Accessing static variable from different webapps
Dear group, I have public class which contains a static variable type integer. I am running different webapps inside single instance of tomcat. I initiated this class in different webapps. I increased the count from a webapp and tried to see it from different webapp. I found that count was not increased in other webapp. It was showing the original count. Am I braking any laws of tomcat security. Thanks for your suggestions. Regards, Anshaj -- v1.2a r TW 0/0/ FD + 0 DSotM 3 100 21.3% 3jan5 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Accessing static variable from different webapps
Put the class in the common or shared classloader. -Tim Anshaj Mathur wrote: Dear group, I have public class which contains a static variable type integer. I am running different webapps inside single instance of tomcat. I initiated this class in different webapps. I increased the count from a webapp and tried to see it from different webapp. I found that count was not increased in other webapp. It was showing the original count. Am I braking any laws of tomcat security. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Accessing static variable from different webapps
Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. Thanks, Anshaj On Thu, 03 Feb 2005 06:41:29 -0500, Tim Funk [EMAIL PROTECTED] wrote: Put the class in the common or shared classloader. -Tim Anshaj Mathur wrote: Dear group, I have public class which contains a static variable type integer. I am running different webapps inside single instance of tomcat. I initiated this class in different webapps. I increased the count from a webapp and tried to see it from different webapp. I found that count was not increased in other webapp. It was showing the original count. Am I braking any laws of tomcat security. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- v1.2a r TW 0/0/ FD + 0 DSotM 3 100 21.3% 3jan5 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Accessing static variable from different webapps
Wrong. Static variables are per *classloader*, not per JVM. -Tim Anshaj Mathur wrote: Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Accessing static variable from different webapps
From: Anshaj Mathur [mailto:[EMAIL PROTECTED] Subject: Re: Accessing static variable from different webapps Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. It's one reference per classloader, not JVM. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. That's because there's a separate classloader for each webapp, along with a few others. Take a look at: http://jakarta.apache.org/tomcat/tomcat-5.0-doc/class-loader-howto.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: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Accessing static variable from different webapps
Yes it makes perfect sense. Thanks for clarify some of the basic concepts to me. Regards, Anshaj On Thu, 3 Feb 2005 06:52:55 -0600, Caldarale, Charles R [EMAIL PROTECTED] wrote: From: Anshaj Mathur [mailto:[EMAIL PROTECTED] Subject: Re: Accessing static variable from different webapps Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. It's one reference per classloader, not JVM. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. That's because there's a separate classloader for each webapp, along with a few others. Take a look at: http://jakarta.apache.org/tomcat/tomcat-5.0-doc/class-loader-howto.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: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] -- v1.2a r TW 0/0/ FD + 0 DSotM 3 100 21.3% 3jan5 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Accessing static variable from different webapps
For more information on tomcat's classloading concept have a look at: http://jakarta.apache.org/tomcat/tomcat-5.5-doc/class-loader-howto.html As you can see there, Tomcat instantiates a classloader for each web application. So if you put a class - let's say Global - inside the WEB-INF/classes directory of each of two of your web applications, it will be loaded twice. As a fact, a static variable of the Global class - let's say Global.myVar - will exist twice too! But if you put your Global class into the %TOMCAT_HOME%/shared/classes directory ONLY (important: you must remove all occurences of your Global class from the webapps-classes directories to make this work!), it will be loaded by the shared-classloader. Because of the fact that the shared classloader is the parent classloader of all webapp-classloaders, every web-application can access the classes loaded by the shared classloader. But holding resources in static variables inside the shared/classes directory there is not recommmended! Better add a JNDI-resource to your Tomcat's JNDI-context! This is done in server.xml inside the GlobalNamingResources-element* *(see http://jakarta.apache.org/tomcat/tomcat-5.5-doc/config/globalresources.html). Best regards, Tex Thanks for your reply. I think JVM rules said that there should be 1 reference per JVM for a static variable. Tomcat class loader creates separate instance of a static variable for each webapps. I am just trying to understand how class loader works in tomcat. Thanks, Anshaj On Thu, 03 Feb 2005 06:41:29 -0500, Tim Funk [EMAIL PROTECTED] wrote: Put the class in the common or shared classloader. -Tim Anshaj Mathur wrote: Dear group, I have public class which contains a static variable type integer. I am running different webapps inside single instance of tomcat. I initiated this class in different webapps. I increased the count from a webapp and tried to see it from different webapp. I found that count was not increased in other webapp. It was showing the original count. Am I braking any laws of tomcat security. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
