Re: DOMWrite an HTMLDocument

"Roger C. Soares" <[email protected]>
Newsgroups gmane.comp.java.enhydra.barracuda.general
Message-ID <[email protected]> 
Hi Jake,

Thanks for the information and code samples. I have to study it better 
to see if it fits my case. You gave me lots of new information! :)

Well, internally, my system works with XML and the W3C Document. HTML is 
just one source of data, and somehow it needs to be imported to an XML 
Document so I can do something with it. In the end I have an XML 
Document, but sometimes it is interesting to format it to HTML to send 
to a browser, that's where I was using the HTMLDocumentFactory. I was 
creating a basic HTML document and importing the nodes from the XML 
Document, so the DOMWriter would use the HTML formatter.

As the createBasicDocument() returns an HTMLDocument I dont't have how 
to set the encoding without getting the DOMImplementation. Also, I can't 
dynamically populate this HTMLDocument and serialize it any more:

HTMLDocument themeDoc = HTMLDocumentFactory.createBasicDocument();
themeDoc.getBody().appendChild(themeDoc.createTextNode("test"));
new DefaultDOMWriter().write(themeDoc, context.getResponse());

I don't really understand well how XMLC works, maybe this 
HTMLDocumentFactory was intended to be an XMLC only class. But as it 
returns an org.w3c.dom.html.HTMLDocument I was expecting it to be valid...

Thanks,
Roger.

--
Jacob Kjome wrote:
> At 12:10 AM 7/14/2003 -0300, you wrote:
> 
>> Hi Jake,
>>
>> For the transformation I read XML files from the disk and change 
>> dynamically the DOM tree with the parameters from the request.
>>
>> The JAXP API has a method to load an XML from an InputStream:
>> javax.xml.parsers.DocumentBuilder.parse(InputStream is)
>> doesn't it work for you?
> 
> 
> Sure it does.  I was wondering specifically how you were using XMLC to 
> do this.  Apparently you are not using XMLC to do this, though.
> 
> In the example reduced test case you provided where XMLC was bombing on 
> a NullPointerException, that is actually to be expected.  Here is the 
> explanation from David Li of XMLC fame...
> 
> <quote name="David Li">
> It should throw a null point exception. When you call 
> createBasicDocument(), it creates a XercesLinkedHTMLDocument whose 
> xmlobject is null.
> 
> encoding = ((XMLObjectLink)document).getXMLObject().getEncoding();
> 
> Is calling getEncoding on the null object. There is no reason to call 
> the createBasicDocument and serialize it right away.
> </quote>
> 
> That's why I was wondering how you were creating the document.  It seems 
> you had to be using XMLC to load up your document because it had to be 
> an instance of XMLObjectLink to call getEncoding().  Until I see how you 
> were attempting to load the document via XMLC and getting the 
> NullPointerException, this isn't a bug and it won't be fixed in the 
> XMLC-2.2 final release.  The release will be done very early this week, 
> so get as much info to me now as you can if you want it working the way 
> you think it should work.
> 
>> Now, to the HTML parsing. I don't use XMLC, I call JTidy directly 
>> instead. It is an ugly hack, I remember having some problems when I 
>> wrote this code, but if there is another way to do it that doesn't 
>> involve too many hours to implement I'm willing to update it. Tell me 
>> what you need and I'll research if I can come up with a code you can 
>> use and then I'll just use DOMLoader.
>>
>> My HTML parser works like this:
>> 1) Read the HTML file from the web
>> 2) Save it to a temp file
>> 3) Parse the temp file with JTidy and store the output in an String
>> 4) Parse this String with Xerces to finally have a DOM tree
>>
>> I don't remember why I had to create a temp file, I think I can remove 
>> this step because JTidy can read from an InputStream. And I had to get 
>> JTidy's output on a String and parse it again because the DOM tree 
>> generated by JTidy was not compatible with the W3C DOM API... :(
>>
>> Here is the code:
>> -- 
>> Tidy tidy = new Tidy();
>> FileInputStream in = new FileInputStream(tmpfile);
>> tidy.setMakeClean(false);
>> tidy.setTidyMark(false);        // Don't add Tidy META tag.
>> tidy.setXmlTags(false);
>> tidy.setXmlOut(true);
>> tidy.setRawOut(true);   // avoid mapping values > 127 to entities
>>
>> ByteArrayOutputStream strWriter = new ByteArrayOutputStream();
>> Document tDoc = tidy.parseDOM(in, strWriter);
>>
>> String pageStr = strWriter.toString();
>> pageStr = pageStr.substring(pageStr.indexOf("<html"), 
>> pageStr.length()-1);
>> StringReader strReader = new StringReader("<?xml version=\"1.0\" 
>> encoding=\"ISO-8859-1\"?>\n" + htmlDtd + pageStr);
>>
>> DOMParser domParser = new DOMParser();
>> domParser.parse(new InputSource(strReader));
>> Document doc = domParser.getDocument();
>> -- 
> 
> 
> So, this is what you are doing as a work around to the issue with XMLC 
> that you are having?
> 
>> Humm.. look at that, If DOMLoader can read HTML files I can change all 
>> that by: DOMLoader.load(tmpfile); !!!! Wow! :)
> 
> 
> Yep, but this functionality all depends on the DOMFactory backing the 
> DOMLoader.  The default one for DefaultDOMLoader is the 
> DeferredParsingDOMFactory which, in order to load documents from a file, 
> you need to configure by providing the ServletContext to said factory.  
> This allows it to read context parameters from the web.xml.  Also note 
> that this duplicates the functionality of the XMLCContext from XMLC 
> which would allow you to completely bypass Barracuda's DOMLoader and 
> DOMWriter.  It all depends on what works best for you.  You can see an 
> example of deferred parsing in the XMLC tomcat example.  See the latest 
> CVS for XMLC...
> http://forge.objectweb.org/cvs/?group_id=49
> 
> Note that there are some bug fixes and changes in deferred parsing 
> behavior in the latest XMLC CVS compared to that in Barracuda-1.2.0.  
> Again, XMLC-2.2 will be released this week, so you won't have to wait 
> long for it.  I'm attaching a zip file that has examples of using 
> XMLCContext -vs- using Barracuda's dom loading and writing.  See the 
> web.xml file for examples of the context param configuration I mentioned.
> 
> Note that in addition to the ability to load an hml doc from file, 
> deferred parsing also automatically reloads the file if any change has 
> been made to it.
> 
> Jake
> 
>> Cheers,
>> Roger.
>>
>> -- 
>> Jacob Kjome wrote:
>>
>>> Hi Roger,
>>> Ah... that is quite novel
>>> Out of curiosity, can you provide the code snippets you use to load 
>>> the generated XSL transformation using XMLC for both XML and HTML 
>>> documents?  This might be functionality we'd want to add to the 
>>> DOMLoader.  Right now the DOMLoader loads documents from classes and 
>>> either a file from the file system or classpath, but does not yet 
>>> load a stream (if that is, in fact, what you are doing).  Anyway, 
>>> rather than speculate on what you are doing, I'll just wait for you 
>>> to tell me what you are doing....and we'll try to get the bug worked 
>>> out on the XMLC side of things.
>>> thanks,
>>> Jake
>>> At 10:20 AM 7/11/2003 -0300, you wrote:
>>>
>>>> Hi Jake,
>>>>
>>>> Thanks a lot for the workaround. Unfortunatly it doesn't work for me 
>>>> because my Document comes from an XSL transformation, so it is not a 
>>>> class. I'm using it to generate a preview:
>>>> http://www.livesidebar.com/servlet/SetTheme.event?themeId=doubleTab
>>>>
>>>> Fortunatly, it works for XML Documents, so I'm now generating XHTML 
>>>> which is fine for now. Hopefully this bug will be fixed when I need 
>>>> to generate HTML again, so that's fine :)
>>>>
>>>> Thanks again!
>>>> Cheers,
>>>> Roger.
>>>>
>>>> -- 
>>>> Jacob Kjome wrote:
>>>>
>>>>> Hi Roger,
>>>>> Hopefully this bug will get tracked down and fixed in XMLC before 
>>>>> making the XMLC-2.2 release.  In the meantime, you should be able 
>>>>> to load your document successfully using (exception handling not 
>>>>> provided for brevity)...
>>>>> DOMLoader loader = DefaultDOMLoader.getGlobalInstance();
>>>>> Document doc = null;
>>>>> doc = loader.getDOM(MyPageHTML.class);
>>>>> new DefaultDOMWriter().write(doc, resp);
>>>>> Jake
>>>>> At 10:06 AM 7/10/2003 -0300, you wrote:
>>>>>
>>>>>> Hi Jake,
>>>>>>
>>>>>> I did test the reduced test case. It produces the exact same 
>>>>>> exception from when I get the HTMLDocument from my business object.
>>>>>>
>>>>>> Thanx,
>>>>>> Roger.
>>>>>>
>>>>>> -- 
>>>>>> Jacob Kjome wrote:
>>>>>>
>>>>>>> Hi Roger,
>>>>>>> See comments below...
>>>>>>> At 11:30 PM 7/9/2003 -0300, you wrote:
>>>>>>>
>>>>>>>> Hey Barracuda wizards!
>>>>>>>>
>>>>>>>> I'm updating an application from Barracuda 0.something to 
>>>>>>>> Barracuda 1.2 and I got stuck on this:
>>>>>>>>
>>>>>>>> -- 
>>>>>>>> java.lang.NullPointerException
>>>>>>>>         at 
>>>>>>>> org.enhydra.xml.io.BaseDOMFormatter.getEncoding(BaseDOMFormatter.java:326) 
>>>>>>>>
>>>>>>>>         at 
>>>>>>>> org.enhydra.xml.io.BaseDOMFormatter.(BaseDOMFormatter.java:374)
>>>>>>>>         at org.enhydra.xml.io.HTMLFormatter.(HTMLFormatter.java:99)
>>>>>>>>         at 
>>>>>>>> org.enhydra.xml.io.DOMFormatter.getFormatter(DOMFormatter.java:156)
>>>>>>>>         at 
>>>>>>>> org.enhydra.xml.io.DOMFormatter.write(DOMFormatter.java:192)
>>>>>>>>         at 
>>>>>>>> org.enhydra.barracuda.core.util.dom.DefaultDOMWriter.write(DefaultDOMWriter.java:181) 
>>>>>>>>
>>>>>>>>         at 
>>>>>>>> org.enhydra.barracuda.core.util.dom.DefaultDOMWriter.write(DefaultDOMWriter.java:146) 
>>>>>>>>
>>>>>>>>         at 
>>>>>>>> lsb.presentation.screens.WizardScreen$RenderTabPreviewHandler.handleViewEvent(WizardScreen.java:336) 
>>>>>>>>
>>>>>>>> -- 
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hmm... curious.  Looks like it has more to do with XMLC than 
>>>>>>> Barracuda, though.  As such, I'm cc'ing the XMLC list.
>>>>>>>
>>>>>>>> when writing an HTMLDocument with DefaultDOMWriter.
>>>>>>>>
>>>>>>>> Do you guys have an idea what it could be? The reduced testcase is:
>>>>>>>>
>>>>>>>> HTMLDocument themeDoc = 
>>>>>>>> org.enhydra.xml.xmlc.html.HTMLDocumentFactory.createBasicDocument(); 
>>>>>>>>
>>>>>>>> new DefaultDOMWriter().write(themeDoc, context.getResponse());
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> What exactly are you trying to do?  createBasicDocument() will 
>>>>>>> create an empty HTMLDocument.  Why would you want to write that 
>>>>>>> immediately to output?  It still shouldn't fail with a 
>>>>>>> NullPointerException in BaseDOMFormatter, however.  Looks like it 
>>>>>>> bombs on the second line below...
>>>>>>> } else if (document instanceof XMLObjectLink) {
>>>>>>>         encoding = 
>>>>>>> ((XMLObjectLink)document).getXMLObject().getEncoding();
>>>>>>> }
>>>>>>> Not sure how that would cause a null pointer exception?  If the 
>>>>>>> document is an instance of XMLObjectLink, then the document is, 
>>>>>>> obviously, not null and that whole line should succeed.  Richard, 
>>>>>>> David, Mark, any ideas here?
>>>>>>> Roger, did you actually test your reduced testcase or are you 
>>>>>>> assuming that it is equivalent to another piece of code that is 
>>>>>>> bombing?  If you haven't tested the reduced testcase, can you 
>>>>>>> post your actual code?  It might make a bit more sense.
>>>>>>> Jake
>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> Roger.
>>>>>>>>
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>>>>>>>
>>>>>>>
>>>>>>>
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