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From Ray Holme <>
Subject Re: serialization and newest tomcat
Date Mon, 13 Jan 2014 14:02:46 GMT
Oh, I missed one comment from Daniel before (embedded and I did not see on the first pass,

No, you don't know the application so I would like to explain that some information kept in
the "shared application" beans is very static, needs to be loaded from the DB and is used
everywhere by every user. The number of hits to the DB would quadruple (at minimum) without
these small tables being in memory. I waste maybe 5k of memory to reduce DB use in an active
system and speed up user response time. This would be silly for a system that it NOT active.

On Monday, January 13, 2014 8:38 AM, Ray Holme <> wrote:
OK, that makes perfect sense. We are NOT talking about SESSION objects (where I am defining
session as login to logout of a USER as I mentioned before, perhaps you are defining this
as "while tomcat is up" - I can see either def.). These type beans are all fine, but I would
actually never want them serialized if Tomcat restarts as I would want the user to log back
in for a lot of reasons (but no damage would be caused if they were serialized).

I am talking about java beans that are part of the "application" and shared information available
to all users. These MUST be initialized at startup (they are) and OLD serial copies are defunct
(dangerous as they cause crazy connections to happen) when tomcat is restarted.

Soooo - here is the question:

I would like to allow serialization, but tell Tomcat that certain beans should NOT be resurrected
without me getting warnings in the log file when I don't mark them as serialisable.


Right now, I have stopped warnings but caused other problems.

On Monday, January 13, 2014 8:08 AM, Daniel Mikusa <> wrote:

On Jan 12, 2014, at 8:45 AM, Ray Holme <> wrote:

I haven't been following this thread, but I wanted to clarify a couple comments here just
to make sure someone reading this in the future doesn't get the wrong ideas.

> serialization causes some problems in apache-tomcat-7.0.35

No.  What causes problems is when application objects are placed in the session and they
are not serializable.  This happens because, by default, Tomcat will try to save your session
data when it restarts.  It does this by serializing the data to disk.  Then when it restarts,
it deserializes the data and restores the sessions.

The only other reason why your sessions would need to be serializable is if you're using clustering
(i.e. you add the distributable tag to web.xml).

> I have several applications and run on fedora linux. I have used many releases of fedora
and tomcat.
> My applications are characterized by
>    a) all use a DB (firebird)
>    b) all use both jsp and java servlets
>    c) all use transient java beans for a "round" of interaction (user request - user
>    d) all have 1 or more session java beans for each user (login - logout)
>    e) all have 1 or more application beans (initialized at startup, can refresh, passed
>    f) all have an application specific jar and share a common code jar
> Long ago I added serialization to almost all of the java beans to stop tomcat whining
in the catalina.out file. This worked just fine until the most recent tomcat release.
> On my development machine, java changes build new jars and apache/tomcat must be restarted
to work right. Starting with the new release, problems with connections happened.
> After research, I discovered that the applications were going nuts with connection requests
and xinetd was shutting down the connection factory service. It took a 30 minute wait (or
reboot) to fix this problem. My guess is that the application wide beans were not only being
made fresh as always happens (they use one connection each to initialize), but that the serialized
versions were coming back up and trying to refresh causing lots of strange connections to
be created (if one is not passed, one is made and there are many routines each needing a connection).

I'm not going to pretend to fully understand how your application works, but from what I took
of this explanation it sounds like your application is stuffing a lot of unnecessary things
into the session.  Limiting that or taking a closer look at how those objects are being serialized
is probably something you should consider.

> To solve this problem, I stopped serialization. This solved the problem.

This certainly works, however it's worth nothing that you'll lose any session data when you
restart Tomcat.  For development that's fine, but in production you might not want to do
that.  I guess it depends on your app and what's in the sessions though.

> From the notes I got from others (thanks Mark and ...):
> serialization can be stopped by putting this in many places

The "many places" are context files.  There are several locations where you can configure
your application's context.

> - here is one:
>    appname/META-INF/context.xml
>    <Manager pathname="" />

Again, just watch out as this will prohibit Tomcat from saving session data on restart. 
In other words, all session data is going to be lost on restart.

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