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Re: [ jEdit-devel ] Fwd: javax.xml.parsers.FactoryConfigurationError: MarkerSets + XML plugin
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From: Shlomy R. <sre...@gm...> - 2009-10-02 04:53:41
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Not completely sure about the first point below. I think
JARClassLoader caches only loaded classes; when a plugin is loaded /
started, the plugin class is loaded first. If it does not directly
make use of other classes (of the plugin itself) at startup, then the
other plugin classes are not loaded and also not cached (yet) in
JARClassLoader.
I guess, if you caused the other XML plugin classes to be loaded
during startup, then we would not have this problem in MarkerSets.
But again, I am not sure.
Shlomy
On Thu, Oct 1, 2009 at 9:56 PM, Eric Le Lay
<ker...@us...> wrote:
> Yes, the issue is resolved, but I would be really insterested in
> understanding why there is this failure...
>
> >From what I have gathered :
> - JARClassLoader caches all possible class names, from all the
> plugin jars, at startup (see PluginJAR.init(), JARClassLoader.classHash).
> - this information is used to load a class provided by any given
> plugin, from any given plugin.
> - It is installed everywhere as the class loader
> - In the beanshell console Class.forName("xml.XmlPlugin") fails,
> even if JARClassLoader.classHash.containsKey("xml.XmlPlugin") returns true
> - the DocumentBuilderFactory uses
> Thread.currentThread().getContextClassLoader() to load the class given
> in the system property, and it fails to find the class.
>
> I'm really puzzled, now !
>
>
> Alan Ezust a écrit :
>> FYI, I just rolled back the change in SVN so that I no longer get this
>> exception, so from my point of view, the issue is resolved (I can
>> start up jEdit and XML works), but it would be nice if we could find
>> out what a better solution to this problem is.
>>
>> I am sending a copy of this to jedit-devel because I think it belongs
>> on the whole list.
>> Please in the future, when discussing JarClassLoader issues and other
>> very technical XML plugin issues such as this, please also include the
>> -devel list.
>>
>> On Wed, Sep 30, 2009 at 11:54 AM, Shlomy Reinstein <sre...@gm...
>> <mailto:sre...@gm...>> wrote:
>>
>> I don't know exactly how it works, but I don't think it's the class
>> hash that matters here. Seems to me like XML starts first, but only
>> some of the classes are loaded (maybe only the plugin class). However,
>> the XML startup registers some XML parser classes to be used later by
>> some java classes (that's what the setting of the system properties
>> does).
>> Later, MarkerSets start, and it tries to read the XML using the java
>> classes. The java classes in turn try to load the necessary classes of
>> the XML plugin, but fails to do so because it's in the context of
>> another plugin JAR.
>> I think Matthieu should be able to provide more details on this, as he
>> made some changes to the PluginJAR or to JARClassLoader some time ago
>> in order to allow plugins to find resources in non-plugin jars they
>> depend on.
>>
>> Matthieu, am I correct? Can you explain this?
>>
>> Thanks,
>> Shlomy
>>
>> On Wed, Sep 30, 2009 at 7:29 PM, Eric Le Lay
>> <ker...@us...
>> <mailto:ker...@us...>> wrote:
>> > Hi Shlomy,
>> >
>> > then how can a plugin find classes from a plugin it depends on (e.g.
>> > XmlPlugin find the Console ErrorSource classes) ?
>> > I don't understand the code in JARClassLoader : isn't the
>> classHash a
>> > static member, which makes it accessible to all instances of
>> > JARClassLoader ?
>> >
>> >
>> > Alan Ezust a écrit :
>> >>
>> >>
>> >> ---------- Forwarded message ----------
>> >> From: *Shlomy Reinstein* <sre...@gm...
>> <mailto:sre...@gm...> <mailto:sre...@gm...
>> <mailto:sre...@gm...>>>
>> >> Date: Wed, Sep 30, 2009 at 7:17 AM
>> >> Subject: Re: javax.xml.parsers.FactoryConfigurationError:
>> MarkerSets +
>> >> XML plugin
>> >> To: Alan Ezust <ala...@gm...
>> <mailto:ala...@gm...> <mailto:ala...@gm...
>> <mailto:ala...@gm...>>>
>> >>
>> >>
>> >> Well then, now you know where it comes from... The problem is, in
>> >> jEdit each plugin has its own jar class loader, which does not know
>> >> the other jars. Some time ago Matthieu did some work on this,
>> so that
>> >> MyDoggyPlugin could find the resource files of MyDoggy, but in
>> general
>> >> each plugin can only see itself. So if one plugin modifies some
>> system
>> >> properties to cause java internal classes to instantiate classes of
>> >> its own, then another plugin that gets to instantiate them
>> might not
>> >> find them.
>> >>
>> >> Shlomy
>> >>
>> >> On Wed, Sep 30, 2009 at 4:06 PM, Alan Ezust
>> <ala...@gm... <mailto:ala...@gm...>
>> >> <mailto:ala...@gm... <mailto:ala...@gm...>>> wrote:
>> >>> this is the reply eric sent me privately not to the list.
>> >>>
>> >>>
>> >>> ---------- Forwarded message ----------
>> >>> From: Eric Le Lay <ker...@us...
>> <mailto:ker...@us...>
>> >> <mailto:ker...@us...
>> <mailto:ker...@us...>>>
>> >>> Date: Mon, Sep 28, 2009 at 9:42 AM
>> >>> Subject: Re: javax.xml.parsers.FactoryConfigurationError:
>> MarkerSets + XML
>> >>> plugin
>> >>> To: Alan Ezust <ala...@gm...
>> <mailto:ala...@gm...> <mailto:ala...@gm...
>> <mailto:ala...@gm...>>>
>> >>>
>> >>>
>> >>> Hi Alan,
>> >>> this may have something to do with lines 44-47 of
>> xml/XmlPlugin.java
>> >>>
>> >>> They were commented and I de-commented them to see what happened.
>> >>> Now I see !
>> >>>
>> >>> Something seems broken with the plugin class loader:
>> >>> org.apache.xerces.jaxp.DocumentBuilderFactoryImpl exists in
>> >>> xercesImpl.jar, so it should be found !!!
>> >>>
>> >>> Alan Ezust a écrit :
>> >>>> Something strange happens on jedit startup when I have the trunk
>> >>>> versions of XML and Markets enabled:
>> >>>>
>> >>>>
>> >>>> javax.xml.parsers.FactoryConfigurationError: Provider
>> >>>> org.apache.xerces.jaxp.DocumentBuilderFactoryImpl not found
>> >>>> at
>> >>>>
>> >>>>
>> >>
>> javax.xml.parsers.DocumentBuilderFactory.newInstance(DocumentBuilderFactory.java:129)
>> >>>> at
>> marker.MarkerSetsPlugin.importXml(MarkerSetsPlugin.java:249)
>> >>>> at
>> marker.MarkerSetsPlugin.loadState(MarkerSetsPlugin.java:93)
>> >>>> at marker.MarkerSetsPlugin.start(MarkerSetsPlugin.java:79)
>> >>>> at
>> org.gjt.sp.jedit.PluginJAR.startPlugin(PluginJAR.java:1391)
>> >>>> at
>> org.gjt.sp.jedit.PluginJAR.activatePlugin(PluginJAR.java:752)
>> >>>> at
>> >>>>
>> org.gjt.sp.jedit.PluginJAR.activatePluginIfNecessary(PluginJAR.java:822)
>> >>>> at org.gjt.sp.jedit.jEdit.main(jEdit.java:482)
>> >>>>
>> >>>> Both plugins fail to start (XML and MarkerSets) but if I
>> unload and
>> >>>> reload them from plugin manager, it seems to be fine again.
>>
>>
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>
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