[jdom-interest] jdom 2.0 with generics
Brad Cox
bcox at virtualschool.edu
Mon Aug 8 04:10:34 PDT 2011
Any interest in some simple additions (trivial pom.xml files) to build jdom
with maven?
If so, I'll need a recipe for how to push changes via git. I use mercurial
for everything else.
After years of tolerating W3C DOM, JDOM was like coming home again! Thanks
for resurrecting this!
On Sun, Aug 7, 2011 at 9:32 PM, Jason Hunter <jhunter at servlets.com> wrote:
> I thought I'd send a status update on JDOM 2.0...
>
> In the last couple weeks I've setup a GitHub repository for the work at
> https://github.com/hunterhacker/jdom. Rolf was able to import the CVS
> history fully into GitHub. If you're curious how, he wrote a wiki page in
> the project.
>
> The project has branches for 1.0, 1.1, and 1.1.1. The master branch is for
> 2.0 work, now underway.
>
> Here's a list of improvements we might make (feedback welcome):
> https://github.com/hunterhacker/jdom/wiki/JDOM-2.0
>
> A list of outstanding bugs and RFEs:
> https://github.com/hunterhacker/jdom/issues
>
> If you're new to GitHub one of the perks is you can "watch" the project to
> see what's happening. You can also fork the project, make changes, and send
> us a pull request to incorporate your change into the official tree. That's
> ideal for simple bug fixes or even major Java 5 feature adjustments where
> you might want to work in isolation for a while.
>
> You can follow the project on Twitter at:
> http://twitter.com/#!/jdomproject
>
> And see all commits at:
> http://twitter.com/#!/jdomcommits
>
> We're looking for others who want to be heavily involved in the Java 5
> work. Speak up if that's you.
>
> -jh-
>
> On Jul 22, 2011, at 1:33 PM, Jason Hunter wrote:
>
> > Rolf's been sending in good code for as long as I can remember. :)
> >
> > The reason I've resisted jumping on generics was the backward
> compatibility problem. It's just something you can do without breaking old
> code, as Rolf's email explains in some good detail.
> >
> > I do think it's causing JDOM to be seen in a negative light, so we should
> do something about it.
> >
> > The alternative package approach is probably the best road forward. It's
> a bit uglier, but it makes explicit the breakage, and means you can use JDOM
> 1.1 and JDOM 2.0 classes in the same project without conflict (an issue that
> arises if a project uses both Library X and Library Y which both depend on
> JDOM and maybe not the same versions).
> >
> > I suppose org.jdom2 is the best package. Suitable for a 2.0 release.
> >
> > I don't have a lot of time to do coding but I'll be happy to coordinate.
> Rolf, why don't you send me the code and I'll put it in revision control.
> Some others have sent in versions as well. We can decide which one's best
> and work on a 2.0 release.
> >
> > Maybe we should move the code to github while we're at it?
> >
> > Send in thoughts...
> >
> > -jh-
> >
> > On Jul 21, 2011, at 4:56 PM, Rolf Lear wrote:
> >
> >> As an overview of what I did:
> >>
> >> README.Java5
> >> ============
> >>
> >> Here are the more significant changes made for the Java5 proposed
> solution.
> >>
> >> 1. Modified org.jdom.filter.Filter to be generic.
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> This allows Filter Implementations to return specific Content types.
> >> In addition, instead of returning boolean, it instead must fulfill the
> contract to return the input content cast in to
> >> the same type as the Filter <T>. Returning a null value indicates the
> filter does not match.
> >>
> >> public interface Filter <T extends Content> extends java.io.Serializable
> {
> >> public T filter(Content content);
> >> }
> >>
> >> Here is the JDom1.1 interface:
> >> public interface Filter extends java.io.Serializable {
> >> public boolean matches(Object obj);
> >> }
> >>
> >> Significant implications of this change include the change of the method
> name from 'matches' to 'filter'.
> >> This is somewhat mitigated by the 'AbstractFilter' method 'matches'
> which is simply:
> >> return filter(content) != null;
> >>
> >> Another 'regression' is that the filter and matches method now require
> at least 'Content' instead of 'Object' data.
> >> A direct implication of this is that you can not have a Filter on
> Document Objects. I could not find any examples of
> >> this in the project, or my work environment. It seems to be somewhat
> 'safe'. This is especially true because Filters
> >> are primarily used as input to the Parent.getContent(Filter) method,
> which, since the content can never be Document,
> >> implies this change is probably benign. It does make some code redundant
> in class ContentFilter.
> >>
> >> All classes that implement Filter have been modified to be sensible.
> >>
> >> This is the change that makes the code:
> >> List<Element> kids = someelement.getChildren();
> >> possible.
> >>
> >>
> >> 2. Modified Parent to be generic.
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >>
> >> This allows for the method:
> >> Parent<T> addContent(Content content)
> >> to be added to the Parent interface, and still return the right type...
> >>
> >>
> >> 2. Rewrote much of ContentList (again)
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> Three motivators for this change:
> >> a) Generics - so much had to change to accomodate Generics, seems this
> was the core impact.
> >> b) Compliance - set() method on Collections are not supposed to impact
> Concurrent Modification,
> >> but JDom did. Changed this so that set() does not impact concurrent
> status.
> >> c) Performance - modified FilterList and FilterListIterator to work on
> an as-needed basis. Will
> >> cache known content, but will only filter data on an as-needed
> basis, or 'lazy' basis. Need to
> >> devise tests to measure performance impact, but things like
> element.getChildren.iterator() will be
> >> much faster.
> >>
> >> Another motivator was conformance with existing concepts, specifically
> List.subList(int,int). The paradigm for
> >> SubList is that modifications to the base list would cause concurrent
> exception in subList. This seems to be
> >> appropriate for FilterLists too, but, too much code depends on
> essentially dynamic/concurrent modification
> >> to make the change. The old behaviour remains.... leading to potentially
> odd things in FilterList iterators.
> >>
> >>
> >> 3. Removed complexities in JDOMException
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> In Java5 we have the initCause method embedded in to Throwable. We don't
> need to jump through hoops any more.
> >>
> >>
> >> 4. Removed TextBuffer class
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> This was an attempt to be a better performing StringBuffer. With Java5's
> StringBuilder, we don't need to worry.
> >>
> >>
> >> 5. Created AttributeType Enum
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> This makes new attributes easy to manage, and also eliminates a bunch of
> org.jdom.test.* stuff.
> >> This also has probably the largest impact on existing code because of
> the requriement to change things like
> >> Attribute att = new Attribute ("name", "somevalue",
> Attribute.ID_TYPE);
> >> to
> >> Attribute att = new Attribute ("name", "somevalue",
> AttributeType.ID_TYPE);
> >>
> >> On the other hand, it is all now TypeSafe ;-)
> >>
> >>
> >> 6. Created Annotation CVS_ID
> >> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >> This is used instead of the static field CVS_ID. This is set up to be an
> annotation to a class. Previously we had:
> >> public class Attribute implements Serializable, Cloneable {
> >> private static final String CVS_ID = "@(#) $RCSfile:
> Attribute.java,v $ $Revision: 1.56 $ $Date: 2007/11/10 05:28:58 $ $Name:
> $";
> >> ....
> >>
> >> we now instead have:
> >> @CVS_ID("@(#) $RCSfile: Attribute.java,v $ $Revision: 1.56 $ $Date:
> 2007/11/10 05:28:58 $ $Name: $")
> >> public class Attribute implements Serializable, Cloneable {
> >>
> >> The motivation for this is because Eclipse complains when there are
> unused private members... but, this is perfect
> >> fodder for annotations.
> >>
> >> As a result, all org.jdom.* classes in the main repo have been modified
> to use the annotation rather than the static String.
> >>
> >> As an excercies later, we will be able to programatically be able to
> determing all the CVS details at runtime using
> >> the annotations, and I have tested that
> >>
> >>
> >> 7. General Tidy-up.
> >> ^^^^^^^^^^^^^^^^^^^
> >>
> >> Fixed all JavaDoc comments where applicable. Ensured @Override was
> specified where appropriate, etc.
> >> basically, I set strict rules in Eclipse, and then fixed all issues.
> >>
> >>
> >> 8. JavaDoc
> >> ^^^^^^^^^^
> >> All public and protected classes, methods, and fields have had their
> JavaDoc entries inspected and completed.
> >>
> >>
> >> 9. build.xml
> >> ^^^^^^^^^^^^
> >>
> >> set Java compliance levels, JDom version number.
> >>
> >> TESTS
> >> =====
> >> org.jdom.test.* has been modified to use and test the new code properly.
> >> Alltests was modified to include some suites that were not included.
> >> Alltests has been run, and all run tests have passed.
> >>
> >>
> >> CONTRIB
> >> =======
> >> All code has been modified to do what appears to be sane usage of the
> new JDom, but testing has not been done.
> >>
> >> STILL TO DO
> >> ===========
> >>
> >> FilterIterator seems clunky still. Especially the XXX warning.
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> On 21/07/2011 7:19 PM, Rolf Lear wrote:
> >>>
> >>> I did a JDOM conversion a while back. Made the code available to those
> who were interested.
> >>>
> >>> There are a few 'gotchas', and most of the Generics implementation
> relies on 'hiding' explicit casting inside of the ContentList class.
> >>>
> >>> It makes code that compiles against the JDOM cleaner, but does not
> actually improve any reliability...
> >>>
> >>> Additionally, the XPath support is pretty much impossible to
> accomplish.
> >>>
> >>> Let me dig up the code.... Or, rather, anyone interested should mail me
> directly.
> >>>
> >>> Rolf
> >>>
> >>
> >> _______________________________________________
> >> To control your jdom-interest membership:
> >> http://www.jdom.org/mailman/options/jdom-interest/youraddr@yourhost.com
> >
> >
> > _______________________________________________
> > To control your jdom-interest membership:
> > http://www.jdom.org/mailman/options/jdom-interest/youraddr@yourhost.com
>
>
> _______________________________________________
> To control your jdom-interest membership:
> http://www.jdom.org/mailman/options/jdom-interest/youraddr@yourhost.com
>
--
Cell: 703-594-1883
Blog: http://bradjcox.blogspot.com
Web: http://virtualschool.edu
Manassas VA 20111
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