Re: PersistentManager and ClassNotFoundException

[Christopher Schultz]

Jakub,

On 5/24/24 09:31, Jakub Królikowski wrote:
On Fri, May 24, 2024 at 11:23 AM Mark Thomas <ma...@apache.org> wrote:
Can you provide the simplest web application (with source) that
replications the problem?

Mark


On 23/05/2024 23:45, Jakub Królikowski wrote:
Hi,

I'm working with Tomcat 10.1.

When a user starts using the store in my web application, I save the
ShopCart object on the "cart" session attribute.
I want the "cart" attributes to return to the session after restarting
the
app.


To enable session persistence I added

<Manager pathname="SESSIONS.ser" />

to the Context. It loads the StandardManager.

And this works fine - after reload / restart the object "ShopCart" is
back
in the session.



I want to experiment with PersistentManager. Tomcat docs says: "
The persistence across restarts provided by the *StandardManager* is a
simpler implementation than that provided by the *PersistentManager*. If
robust, production quality persistence across restarts is required then
the
*PersistentManager* should be used with an appropriate configuration.

"

I hope for a Listener of deserialization of the session attributes.

The new Manager configuration looks like this:

<Manager className="org.apache.catalina.session.PersistentManager"
maxActiveSessions="2" saveOnRestart="true">

<Store className="org.apache.catalina.session.FileStore" directory=
"c:\tomcat10\sessionperm"/>

</Manager>

But it doesn't work. After restart I get this exception:


java.lang.ClassNotFoundException: ....ShopCart

at

org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1332)

at

org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1144)

at java.base/java.lang.Class.forName0(Native Method)

at java.base/java.lang.Class.forName(Class.java:534)

at java.base/java.lang.Class.forName(Class.java:513)

at

org.apache.catalina.util.CustomObjectInputStream.resolveClass(CustomObjectInputStream.java:158)

at
java.base/java.io
.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:2061)

at
java.base/java.io
.ObjectInputStream.readClassDesc(ObjectInputStream.java:1927)

at
java.base/java.io
.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2252)

at
java.base/java.io
.ObjectInputStream.readObject0(ObjectInputStream.java:1762)

at
java.base/java.io
.ObjectInputStream.readObject(ObjectInputStream.java:540)

at
java.base/java.io
.ObjectInputStream.readObject(ObjectInputStream.java:498)

at

org.apache.catalina.session.StandardSession.doReadObject(StandardSession.java:1198)

at

org.apache.catalina.session.StandardSession.readObjectData(StandardSession.java:831)

at org.apache.catalina.session.FileStore.load(FileStore.java:203)

at
org.apache.catalina.session.StoreBase.processExpires(StoreBase.java:138)

at

org.apache.catalina.session.PersistentManagerBase.processExpires(PersistentManagerBase.java:409)

at

org.apache.catalina.session.ManagerBase.backgroundProcess(ManagerBase.java:587)

at

org.apache.catalina.core.StandardContext.backgroundProcess(StandardContext.java:4787)

at

org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1172)

at

org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1176)

at

org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1176)

at

org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1154)

at

java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)




at

java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:358)

at

java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)

at

java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)

at

java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)

at

org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:63)

at java.base/java.lang.Thread.run(Thread.java:1583)


I guess this means that the two managers use ClassLoader differently.
How to get the PersistentManager to work in this case?

Best regards,
--
Jakub Królikowski


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Hi Mark,
It seems to me that this can be tested on any application.
In Tomcat 10.1, if any session attribute is an instance of a new public
class (unknown to Tomcat and to Tomcat class loader), implementing
java.io.Serializable,
then on reloading the application PersistanceManager (configured as in the
first message) crashes with ClassNotFoundException. StandardManager works.
I don't know if this problem occurred in earlier versions of Tomcat.

If you fail to reproduce this bug, let me know, I will prepare a simple web
app.

Where is your <Manager> configuration located? It *should* be inside 
your <Context> located in META-INF/context.xml in your web application. 
If it's in there, then everything it does should be in the context (and 
ClassLoader) of your web application -- where your classes should be 
locatable.

If you have it anywhere else, it probably won't work the way you expect 
it to work.

-chris

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