Re: Service Provider mechanism and javax.imageio.spi.ServiceRegistry

Speaking of properties files, ordering and comments, does anyone know
of a readily available SAX handler-like or DOM-like parser for
properties files? (Seems like the right way to have written that code
in the first place...)

On 11/3/07, Attila Szegedi <[email protected]> wrote:
> It's easy to dicover and process these files with a bit of custom code. I
> have it in few places, most notably here:
>
> <http://dynalang.svn.sourceforge.net/viewvc/dynalang/trunk/dynalang/src/org/dynalang/mop/impl/AutoDiscovery.java?view=markup>
>
> Something like this'll return you a list of service instances for all
> declared services within a ClassLoader's scope:
>
> <T> static List<T> getServices(Class<T> serviceItf, ClassLoader cl)
> throws IOException, InstantiationException, IllegalAccessException,
> ClassNotFoundException {
>      List<T> list = new LinkedList<T>();
>      String path = "/META-INF/services/" + serviceItf.getClass().getName();
>      Enumeration<URL> urls;
>      if(cl == null) {
>          urls = ClassLoader.getSystemResources(path);
>      }
>      else {
>          urls = cl.getResources(path);
>      }
>      for(;urls.hasMoreElements();) {
>          URL url = urls.nextElement();
>          InputStream in = url.openStream();
>          try {
>              Properties props = new Properties();
>              props.load(in);
>             for (Object className : props.keySet()) {
>                  T serviceInstance = (T)Class.forName(
>                      className.toString(), true, cl).newInstance());
>              list.add(serviceInstance);
>          }
>          finally {
>              in.close();
>          }
>      }
>      return list;
> }
>
> I'm using Properties object 'cause I get skipping of empty lines and
> handling of # comments for free. It does not guarantee you that you'll
> instantiate the objects in the order they were declared in individual
> files though, but I can live with that...
>
> That's it :-)
>
> BTW, it stinks that java.util.Properties doesn't extend Hashtable<String,
> String>...
>
> Attila.
>
> On Wed, 31 Oct 2007 15:03:49 +0100, Bertrand Delacretaz
> <[email protected]> wrote:
>
> > On 10/31/07, Bertrand Delacretaz <[email protected]> wrote:
> >
> >> ...But it feels a bit weird to have this in javax.imageio.spi, is there
> >> a
> >> better alternative?...
> >
> > Someone mentioned off-list the java.util.ServiceLoader class, which
> > looks like what I'm looking for, but it's available starting with Java
> > 1.6 only.
> >
> > -Bertrand
> >
> --
> home: http://www.szegedi.org
> weblog: http://constc.blogspot.com
>
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