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From "Craig R. McClanahan" <craig...@apache.org>
Subject RE: Digester yielding IllegalAccessException in CallMethodRule, SetNextRule
Date Wed, 05 Dec 2001 06:40:58 GMT


On Tue, 4 Dec 2001, Donnie Hale wrote:

> Date: Tue, 4 Dec 2001 22:44:09 -0500
> From: Donnie Hale <donnie@haleonline.net>
> Reply-To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
> To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
> Subject: RE: Digester yielding IllegalAccessException in CallMethodRule,
>      SetNextRule
>
> Craig,
>
> Thanks for the prompt response. If I understand your second case, I tried
> it, and it worked as I wanted:
>
> // Callback.java
> public class Callback implements Reader.WebXmlFileDigestion
> {
>     public Callback(Driver d)
>     {
>         driver_ = d;
>     }
>
>     public void parseError(Throwable t) throws Exception
>     {
>         t.printStackTrace();
>     }
>
>     public void setServletMapping(
>         String servletName, String urlPattern)
>     {
>         driver_.addServletMapping(servletName, urlPattern);
>     }
>
>     Driver driver_;
> }
>
> Then, in Driver.java, I used
>
>         reader.digestWebXmlFile(new Callback(this));
>
> instead of passing the anonymous implementing class.
>

OK, so we know it definitely has something to do with visibility of the
called class.

> I'll have to see if I have Sun's 1.3 JDK around to try. If not, it could be
> a while, as I only have IDSL access. :)
>
> One more, related, thing, since you're in the know.

I better be, since I wrote Digester :-).

> Is it possible to
> implement an interface with methods which have package scope though the
> interface methods are public? I don't care that some unknown future entity
> implements the interface; but I don't want the methods in the implementation
> of it that I care about to be publicly accessible. My copy of the language
> spec is at work...
>

I'm sure it's feasible to implement access via reflection (which is what
Digester uses) to methods defined public through an interface - we ran
into a similar case in BeanUtils and solved it be looking up an
appropriate java.lang.reflect.Method object correctly.  I'm not sure what
happens when you shadow a package-private method with a public one -- will
have to check on that.  However, AFAIK, the class itself has to be public
for any of this to work.

> Thanks much,
>
> Donnie
>

Craig


>
> -----Original Message-----
> From: craigmcc@localhost [mailto:craigmcc@localhost]On Behalf Of Craig
> R. McClanahan
> Sent: Tuesday, December 04, 2001 10:08 PM
> To: Jakarta Commons Developers List
> Subject: Re: Digester yielding IllegalAccessException in CallMethodRule,
> SetNextRule
>
>
> Hi Donnie,
>
> IIRC, Digester only knows how to call public methods of public classes --
> and an anonymous inner class isn't public.
>
> Could you try two things for me?
> * Try this under the Sun JDK just to see if the behavior is different
> * Try this where the driver class is a regular public class,
>   rather than an inner class
>
> That will help us narrow down where the difficulty is.
>
> Craig
>
>
> On Tue, 4 Dec 2001, Donnie Hale wrote:
>
> > Date: Tue, 4 Dec 2001 22:15:20 -0500
> > From: Donnie Hale <donnie@haleonline.net>
> > Reply-To: Jakarta Commons Developers List <commons-dev@jakarta.apache.org>
> > To: commons-dev@jakarta.apache.org
> > Subject: Digester yielding IllegalAccessException in CallMethodRule,
> >      SetNextRule
> >
> > I searched the list archives and didn't see anything directly on-topic.
> > Sorry if I missed it. Also, this is likely a normal Java issue, but I'm
> not
> > getting it. :(
> >
> > Here's a very pared down example which reproduces my problem exactly:
> >
> > // Driver.java
> > public class Driver
> > {
> >     public static void main(String[] args)
> >     {
> >         try
> >         {
> >             Driver driver = new Driver();
> >             driver.parseWebApp(new Reader());
> >         }
> >         catch (Exception e)
> >         {
> >             e.printStackTrace();
> >         }
> >     }
> >
> >     public void Driver()
> >     {
> >     }
> >
> >     public void parseWebApp(Reader reader) throws Exception
> >     {
> >         reader.digestWebXmlFile(
> >             new Reader.WebXmlFileDigestion()
> >             {
> >                 public void parseError(Throwable t) throws Exception
> >                 {
> >                     t.printStackTrace();
> >                 }
> >
> >                 public void setServletMapping(
> >                     String servletName, String urlPattern)
> >                 {
> >                     addServletMapping(servletName, urlPattern);
> >                 }
> >             }
> >         );
> >     }
> >
> >     public void addServletMapping(String servletName, String urlPattern)
> >     {
> >         System.out.println("Mapping read: " + servletName + " => " +
> > urlPattern);
> >     }
> > }
> >
> > // Reader.java
> > import java.io.InputStream;
> > import java.io.IOException;
> > import java.net.URL;
> > import org.xml.sax.Attributes;
> > import org.xml.sax.SAXException;
> > import org.apache.commons.digester.Digester;
> > import org.apache.commons.digester.Rule;
> >
> > public class Reader
> > {
> >     public static interface WebXmlFileDigestion
> >     {
> >         public void parseError(Throwable t) throws Exception;
> >
> >         public void setServletMapping(String servletName, String
> > urlPattern);
> >     }
> >
> >     public void Reader()
> >     {
> >     }
> >
> >     public void digestWebXmlFile(WebXmlFileDigestion callback)
> >         throws Exception
> >     {
> >         // Prepare a Digester to scan the web application deployment
> > descriptor
> >         Digester digester = new Digester();
> >         digester.push(callback);
> >         digester.setDebug(1);
> >         digester.setNamespaceAware(true);
> >         digester.setValidating(false);
> >
> >         // Register our local copy of the DTDs that we can find
> >         for (int i = 0; i < registrations_.length; i += 2)
> >         {
> >             URL url = this.getClass().getResource(registrations_[i+1]);
> >             if (url != null)
> >             {
> >                 digester.register(registrations_[i], url.toString());
> >             }
> >         }
> >
> >         // Configure the processing rules that we need
> >         digester.addCallMethod("web-app/servlet-mapping",
> >             "setServletMapping", 2);
> >         digester.addCallParam("web-app/servlet-mapping/servlet-name", 0);
> >         digester.addCallParam("web-app/servlet-mapping/url-pattern", 1);
> >
> >         InputStream input= null;
> >         try
> >         {
> >             input = this.getClass().getResourceAsStream("web.xml");
> >             digester.parse(input);
> >         }
> >         catch (Throwable e)
> >         {
> >             callback.parseError(e);
> >         }
> >         finally
> >         {
> >             if (input != null)
> >             {
> >                 input.close();
> >             }
> >         }
> >     }
> >
> >     protected static final String registrations_[] =
> >     {
> >         "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN",
> >         "/org/apache/struts/resources/web-app_2_2.dtd",
> >         "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN",
> >         "/org/apache/struts/resources/web-app_2_3.dtd"
> >     };
> > }
> >
> > The object on which the method call is to be invoked is an instance of an
> > anonymous inner class which implements a public (nested) interface. All
> the
> > methods on the interface and its anonymous implementation are public. All
> > the methods on Driver and Reader are public. Yet when I run this, I get:
> >
> > java.lang.IllegalAccessException: Driver$1
> >         at java.lang.reflect.Method.invoke(Native Method)
> >         at
> > org.apache.commons.digester.CallMethodRule.end(CallMethodRule.java:308)
> >         at
> > org.apache.commons.digester.Digester.endElement(Digester.java:757)
> >         at
> > org.apache.xerces.parsers.SAXParser.endElement(SAXParser.java:1403)
> >         at
> >
> org.apache.xerces.validators.common.XMLValidator.callEndElement(XMLValidator
> > .java:1480)
> >         at
> >
> org.apache.xerces.framework.XMLDocumentScanner$ContentDispatcher.dispatch(XM
> > LDocumentScanner.java:1149)
> >         at
> >
> org.apache.xerces.framework.XMLDocumentScanner.parseSome(XMLDocumentScanner.
> > java:381)
> >         at
> org.apache.xerces.framework.XMLParser.parse(XMLParser.java:1081)
> >         at org.apache.commons.digester.Digester.parse(Digester.java:1206)
> >         at Reader.digestWebXmlFile(Reader.java:53)
> >         at Driver.parseWebApp(Driver.java:23)
> >         at Driver.main(Driver.java:9)
> >
> > I'm guessing this has something to do with the "Driver$1" being the
> > classname. But it sure seems like I've done stuff like this before, just
> > possibly not through reflection. Do I have to go to the extreme of making
> > the interface implementation non-anonymous to have any hope of getting
> this
> > to work?
> >
> > BTW, I'm using IBM's JDK 1.3 on Win2K.
> >
> > Thanks much,
> >
> > Donnie
> >
> >
> > --
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> >
> >
>
>
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