The standardmanager persist sessions across reload using serialization. That mean all object in session must be serializable. An object is serializable if 1) it implements the Serializable interface (see also the externalizable interface which give more control on serialization) 2) it has an no-parameter constructor 3) all it's instance fields are serializable
The serialization process does not store or restore static field, because those are class wide and not related to object instance. En l'instant précis du 07/05/07 09:20, mélanie langlois s'exprimait en ces termes: > Hello, > > We are running tomcat 5.0.28, and we have a problem with the > standardManager when restarting our application. We have a > NullPointerException when the StandardManager loads a session > object.This object has static fields calling another class method (to > obtain the bundles key for some page title). However, this second > class has not been iniatlized yet, Ok, you have class A static initialization assume some class B static methods calls were before (maybe during a servlet initialization , a context listerner or filter job), this is a big design problem, you can not easily be sure of when class A will be static initialized by classloader. This is weak design as it's very difficult to be 100% sure of class initialization order in a code. > and I can see that the standard Manager initialize this class after. > But it's too late, the NullPointerException makes it impossible to > access the index page properly. We need to restart. Standard Manager does not initialize classes, it initialize instances of those classes. It's the classloader that does the job of static initialization of classes. > How does the standard manager works ? Does it try to load all static > objects first ? persistence is done only on object instances, the classloader does static initialization of class members, standardManager does unserialization, all unserialization does is a Object o = someClass.newInstance(); and then put unserialized values in 'o' fields. > Why the startup is working fine when the standard manager is not > launched (no session persisted )? Because order in which your classloader statically initialize your classes is not the same if you don't try at startup to unserialize user session. Possible solutions: 1) revise design of your session objects, those should be serializable to be in session. Move the static field to another object shared by all users. 2) Don't put this problematic object in the session. 3) Don't use session persistence (aka don't use a Manager) > > Thanks, > > Mélanie > > _________________________________________________________________ > Gagnez des pc Windows Vista avec Live.com http://www.image-addict.fr/ > > > --------------------------------------------------------------------- > To start a new topic, e-mail: users@tomcat.apache.org > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
