Re: w3c html dom versioning oddities

Hi Jake,

The problem is that the HTML DOM Level 2 early Working drafts changed the API of some 
HTMLElements, but not the package names (see 
http://www.w3.org/TR/2000/WD-DOM-Level-2-HTML-20001113/java-binding.html). Before the 
final recommendation the package names where changed to org.w3c.dom.html2, thus ending 
the confusion about incompatibility.

The source of the problem is that people were using the interfaces from those early Level 
2 interfaces and getting into compatibility issues. This poped up again on the Xerces-J 
developer list when Neeraj discovered incompatibilities with JDK1.4, because JDK1.4 ships 
with such an early Level 2 api (having the old package name, but some new methods). See 
thread 'Xerces DOM HTML impl' on the developer list.

Since, the HTML DOM implementation provided by Xerces is really DOM Level 1, they are 
shipping the 'real' DOM Level 1 API with Xerces. However, this may result in some tricky 
classpath issues if you are using JDK1.4, since the Xerces classes don't provide the 
additional methods found in JDK1.4 (HTML DOM Level 2) but not present in the original 
HTML DOM Level 1 API.

I also think the only clean solution is to use HTML DOM Level 1 API or provide a DOM 
Level 2 Implementation, but then use the final recommendation with the new package names. 
Then you won't have any incompatibilities any more. (But AFAIK, there is no Level 2 
implementation out there :-( ).

Also another point to mention is that HTML DOM Level 2 is based on DOM Level 2 Core, 
while Level 1 is based on, you guessed it,  Core DOM Level 1. So if you are using Xerces 
2, you will use DOM Core Level 2 + HTML DOM Level 1. This seems to works ok. I just found 
some performance drawbacks, for example, HTMLDOcument implements the 'getElementById' 
method in a very slow fashion (searching the tree every time). This method is provided in 
  class Document since Level 2 (and implemented by Xerces as Hashtable lookup).

hope that helps,
    Arno


Jacob Kjome wrote:
> 
> Hello,
> 
> I ran into a very strange issue when using the org.w3c.dom.html 
> interfaces in the release versions of Xerces2 (tried 2.3.0 and 2.4.0).  
> The binaries of the xmlParserAPIs.jar and xml-apis.jar both seem to 
> contain a different version of the html dom interfaces than what comes 
> in the source.  For instance, in the Xerces-J-src.2.3.0.zip download, 
> when I browse to org.w3c.dom.html.HTMLOptionElement.java, said file 
> contains the method setSelected(boolean).  However, when I grab the 
> class file from the binary release (Xerces-J-bin.2.3.0.zip) it 
> HTMLOptionElement does not contain that method.  What gives here?
> 
> Another very confusing thing is the source download for the 2.4.0 
> distribution (Xerces-J-src.2.4.0.zip) contains only a single file in the 
> org.w3c.dom.html package ( HTMLDOMImplementation.java ).  Where are 
> rest?  Well, maybe in the xml-apis--src.zip that comes in the 
> Xerces-J-tools.2.4.0.zip download.  Is that right?  Well, the problem 
> here is that the w3c htm dom being used there is based on the original 
> html dom 1 source released back in 1998.  HTMLOptionElement did not have 
> the setSelected(boolean), only getSelected().  But anyone who has used 
> Xerces-1 has already been used to using newer dom interfaces with 
> setSelected(boolean) in HTMLOptionElement.
> 
> Can anyone clear this up?
> 
> 1.  Why has Xerces2 reverted to an older version of the dom interfaces 
> than Xerces1 had?
> 
> 2.  Why does the source download for Xerces 2.3.0 come with newer 
> versions of the dom interfaces than is released in the 2.3.0 binaries 
> (or any of the Xerces2 binaries, for that matter)?  And why does the 
> source download for Xerces 2.4.0 not have these newer sources anymore?
> 
> 3.  Where did these newer sources come from anyway?  After the html DOM1 
> release, all work was done on the html DOM2 release,. but that falls 
> under a different package named org.w3c.dom.html2.
> 
> 
> Curiously enough, if I extract the org.w3c.dom.html package from the 
> Xerces 2.3.0 source distribution, compile the interfaces, jar the 
> interfaces, and put the jar in my build classpath, everything compiles 
> just fine.
> 
> extremely confused,
> 
> Jake
> 
> 
> 
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