[icedtea-web] RFC: Patch to support plugin classloader sharing

[Dr Andrew John Hughes]

On 21:08 Wed 02 Mar     , Deepak Bhole wrote:
> * Deepak Bhole <dbhole at redhat.com> [2011-03-02 20:55]:
> > * Dr Andrew John Hughes <ahughes at redhat.com> [2011-03-02 20:33]:
> > > On 17:17 Wed 02 Mar     , Deepak Bhole wrote:
> > > > This patch allows plugins from the same page to use the same
> > > > classloader.
> > > > 
> > > > There are known applets (Microsoft Live Meeting, *.map24.com) which rely
> > > > on this behaviour as they try to access static variables from one applet
> > > > through another.
> > > > 
> > > > ChangeLog:
> > > > 2011-03-02  Deepak Bhole <dbhole at redhat.com>
> > > > 
> > > >     Fix RH604061: Microsoft Live Meeting doesn't work
> > > >     Fix PR475: (uk.map24.com) Applet doesn't stop loading
> > > >     * configure.ac: Added checks for sun.misc.JarIndex and
> > > >     sun.misc.URLClassPath
> > > >     * netx/net/sourceforge/jnlp/PluginBridge.java
> > > >     (PluginBridge): Set unique key based on document base (i.e. plugin origin
> > > >     page).
> > > >     * netx/net/sourceforge/jnlp/runtime/JNLPClassLoader.java
> > > >     (getInstance): When trying to compare against file.getFileLocation(),
> > > >     ensure that it is a JNLP application. If it is a plugin and baseloader is
> > > >     not null, marge the loaders.
> > > >     (merge): Use the new addFileURLsFirst function.
> > > >     (addFileURLsFirst): New function. Adds a url to the search path and moves
> > > >     it to the top if it is a file (jar/zip/etc.) path.
> > > >     * NEWS: Updated.
> > > > 
> > > > This should go in 1.1 only for now.
> > > > 
> > > > Cheers,
> > > > Deepak
> > > 
> > > Comments inline.
> > > 
> > > > diff -r 5dbf0f9de599 NEWS
> > > > --- a/NEWS	Wed Mar 02 11:50:30 2011 -0500
> > > > +++ b/NEWS	Wed Mar 02 17:16:03 2011 -0500
> > > > @@ -21,7 +21,9 @@
> > > >    - Use Firefox's proxy settings if possible
> > > >    - RH669942: javaws fails to download version/packed files (missing support for jnlp.packEnabled and jnlp.versionEnabled)
> > > >  * Plugin
> > > > +  - PR475: (uk.map24.com) Applet doesn't stop loading
> > > >    - PR612: NetDania application ends on java.security.AccessControlException: access denied (java.util.PropertyPermission browser read)
> > > > +  - RH604061: Microsoft Live Meeting doesn't work
> > > >  
> > > 
> > > If this is the same bug, then it should be one line:
> > > 
> > > - PR475, RH604061: Allow applets from the same page to use the same classloader
> > > 
> > 
> > Sure.
> > 
> > <snip>
> > > >  New in release 1.0 (2010-XX-XX):
> > > >  
> > > 
> > > This is horrible.  Not only is it going to break if the implementation details of
> > > URLClassLoader change (have you checked OpenJDK7?) but it will fail with any
> > > different implementation of URLClassLoader.  Can you not override a method or
> > > use our own classloader instead of this awful hack?
> > >
> > 
> > Yep, I agree 100% .. (well 99.9 :)) that it is a terrible hack.
> > 
> > The security re-design will rewrite significant parts of the classloader
> > and I am going to make sure that this method, or nothing like it exists
> > thereafter. With this gone, the additional sun.misc.* dep will be gone
> > too. Overriding is not possible because the methods and fields are
> > private. Good point re: OpenJDK7 though. I will take a look.
> > 
> > Until the rewrite, this is really the only way I can think of to share
> > classloaders and not have the client hammer the server by trying to load
> > each class from an http://.../ path first. Bad code aside though, I do
> > think it is worthwhile putting it in in the interim assuming it is
> > stable (which it was in all my testing) with IcedTea and IcedTea6.
> >
> 
> Hold the reply please. I just thought of another solution that might
> work, but it is more disruptive (from code perspective).  I will
> implement it and post it tomorrow and we can discuss which one to adopt
> on the list.
> 

Ok. I'd pretty much prefer most things to this solution.

> Cheers,
> Deepak
>  
> > Thanks,
> > Deepak
> > 
> > 
> >  
> > > >  }
> > > > 
> > > 
> > > 
> > > -- 
> > > Andrew :)
> > > 
> > > Free Java Software Engineer
> > > Red Hat, Inc. (http://www.redhat.com)
> > > 
> > > Support Free Java!
> > > Contribute to GNU Classpath and IcedTea
> > > http://www.gnu.org/software/classpath
> > > http://icedtea.classpath.org
> > > PGP Key: F5862A37 (https://keys.indymedia.org/)
> > > Fingerprint = EA30 D855 D50F 90CD F54D  0698 0713 C3ED F586 2A37

-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

Support Free Java!
Contribute to GNU Classpath and IcedTea
http://www.gnu.org/software/classpath
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Fingerprint = EA30 D855 D50F 90CD F54D  0698 0713 C3ED F586 2A37