[jdom-interest] SaxBuilder.setFeature Bug Report and Fix

[Jason Hunter]

Hi Jason,

Great bug report.  I'll take a look next chance I get.  Brad might beat 
me to it since I'm at XML 2004 this week.  (Hi to anyone else here.)

-jh-

Jason Winnebeck wrote:

> Confirmed to be working in JDOM-b9
> Confirmed to be broken in JDOM-1.0 and JDOM nightly 11-16-2004
> 
> I recently upgraded from JDOM beta 9 to JDOM 1.0, and some of my parsing 
> code broke.  I am using Xerces 2.6 with schema validation for some 
> files, and no schema validation for others.  I reuse the same SAXBuilder 
> to build the files, but I change features after build.
> 
> In JDOM b9, this code works.  Here are select lines of code from the 
> actual program.
> 
> SAXBuilder builder = new SAXBuilder( 
> "org.apache.xerces.parsers.SAXParser", false );
> builder.setFeature( "http://apache.org/xml/features/validation/schema", 
> true );
> 
> builder.setIgnoringElementContentWhitespace( true );
> Document doc = builder.build( new File( "SystemConfigurations.xml" ) );
> 
> //Lines omitted that use doc
> 
> //Lines omitted that construct the userConfigs strings and check to see
> //if file should be loaded
> builder.setFeature( "http://apache.org/xml/features/validation/schema", 
> false );
> doc = builder.build( userConfigs );
> 
> In JDOM 1.0, the schema validation will not be turned off for Xerces, 
> and the second document will not build since it cannot find the schema 
> (and therefore not the definition for the root element).
> 
> Using a debugger and after examining code, I found that 
> SAXBuilder.setFeature only sets an entry in a map which is used in 
> createParser, which is only called once if reuseParser is true (default).
> 
> My first attempt to fix this problem was to add lines to setFeature and 
> setProperty that would set the feature or property directly on 
> this.saxParser if it was not null -- however the methods cannot throw 
> JDOMException and I did not want to change the API.
> 
> So what I did was in SAXBuilder.build( InputSource ) I added a call to 
> setFeaturesandProperties.
> 
> I modified both JDOM 11-16-04 nightly and JDOM 1.0 and the fix worked 
> for both.  I decided for our organization it was best to patch 1.0 than 
> patch and use the nightly, so the line number is based off of JDOM 1.0.
> 
> Insert at line 455:
>               //If the user has changed features or properties, they 
> need to be reset.
>               //In the future we could have a flag to prevent extra work.
>               setFeaturesAndProperties( parser, false );
> 
> Surrounding old code plus new code, starting at line 451:
>             else {
>                 // Reset content handler as SAXHandler instances cannot
>                 // be reused
>                 configureParser(parser, contentHandler);
> 
>               //If the user has changed features or properties, they 
> need to be reset.
>               //In the future we could have a flag to prevent extra work.
>               setFeaturesAndProperties( parser, false );
>             }
> 
> This seems to work for my application, but this is my first time looking 
> at JDOM code and I only spent about 15 minutes examining the class 
> before I made the change, so I do not know how correct the code is.  The 
> one thing I am unsure of is the boolean parameter to 
> setFeaturesAndProperties.  It uses true when createParser is called for 
> my application's case, but the false seems to only set the user 
> features, which are what I'm changing.
> 
> Rationale:
> According to the API documentation, I cannot see a restriction that you 
> are only allowed to call setFeature and setProperty before the first 
> call to build.  Therefore I believe the code changes I proposed here 
> better match the API documentation and expected behavior.
> 
> Jason Winnebeck
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