[jdom-interest] Re: JDOM thread safety

Joseph Bowbeer jozart at csi.com
Sun Aug 13 14:26:04 PDT 2000 

Jason, As I mentioned in private correspondence, I repeat here for
archival and general distribution:

To guarantee thread safety, I recommend that anything that
shouldn't change after construction be declared 'final' and that
anything that can change after construction use 'synchronized' in
some form.

The cached results of lazily evaluated computations would fall
into the latter group, but, as we've discussed, this caching is a
special case because the user isn't aware they're modifying the
document.

As a policy, it seems reasonable to me to decide that the
behind-the-scenes changes should be synchronized by JDOM, and that
synchronization of the other changes should be the responsibility
of the user.

To uphold their end of the bargain, the user can use a read-write
lock.  Doug Lea provides several flavors in his util.concurrent
package, including a re-entrant one.

  http://gee.cs.oswego.edu/dl/cpj/


By the way, if anyone wants to rock their world concerning thread
safety in Java, look at the "Double-Checked Locking is Broken"
document referenced on Bill Pugh's Java Memory Model page:

  http://www.cs.umd.edu/~pugh/java/memoryModel/

--
Joe Bowbeer


--__--__--

Date: Fri, 11 Aug 2000 13:54:27 -0700
From: Jason Hunter <jhunter at acm.org>
To: jdom-interest at jdom.org
Subject: Re: JDOM thread safety

> The point we need to take away is that
> we need to make sure that none of
> our caching logic has race conditions
> for read-only access, and really
> IMHO we *should* guarantee that
> read-only access of JDOM doesn't
> need external synchronization once
> the doc has been built.  A quick code
> review of the most likely problem areas
> makes me think we're OK and have
> always been OK, but we need to make
>  sure we stay OK in the future.




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Subject: [jdom-interest] SaxBuilder and extra features
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Hi,

Sorry if this has been mentioned before but I just joined
list. I need to set some custom features and properties on a
SAX parser. SAXBuilder doesn't give you any access to this
as such. Would it be possible to add either methods such as

setFeature( feature, value )
setProperty( property, value )

or else make it extensible via templated method design
pattern ? I would be happy to do it myself if you like ?

Cheers,

Pete

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Keith Thomas wrote:
> 
> Hi,
> 
> I'm working with a fairly new version of JDOM (a CVS download from last
> week) and can't find details of which version of xerces I should be using. I
> know that a xerces.jar comes with JDOM but I need all the accompanying
> xerces javadocs etc as I sometimes have to work in DOM itself. Apologies if
> this info is somewhere obvious and I've missed it.

You can find Xerces docs at http://xml.apache.org/.

-Edwin
> 
> Regards,
> Keith Thomas
> XTRA On-Line
> _______________________________________________
> To control your jdom-interest membership:
> http://lists.denveronline.net/mailman/options/jdom-interest/youraddr@yourhost.com

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Keith Thomas wrote:
> 
> Hi,
> 
> I'm working with a fairly new version of JDOM (a CVS download from last
> week) and can't find details of which version of xerces I should be using. I
> know that a xerces.jar comes with JDOM but I need all the accompanying
> xerces javadocs etc as I sometimes have to work in DOM itself. Apologies if
> this info is somewhere obvious and I've missed it.

You can find Xerces docs at http://xml.apache.org/.

-Edwin
> 
> Regards,
> Keith Thomas
> XTRA On-Line
> _______________________________________________
> To control your jdom-interest membership:
> http://lists.denveronline.net/mailman/options/jdom-interest/youraddr@yourhost.com

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