Re: [aspectwerkz-user] [patch] DTD error after reload

Hi Mattias.

Sorry for missing your mail on the dev list. I sounds like a logical
explaination. I have not tested it nor experienced it. But I am taking
your word for it. I will try it out and add the fix to the dist.

Thanks a lot for tracking it down.

It is great when the only bugs you are getting are bugs like this,
then you know that the framework is stable.

/Jonas

On 11/22/05, Mattias Jiderhamn <[email protected]> wrote:
>  [Nobody answered this in the dev list, so I'll givet it a try on the user
> list]
>
>  I believe I have finally tracked down and fixed a problem with reading the
> DTD file after web application reload. Since long we have experienced now
> and then that - using online weaving - after the application has been
> reloaded a couple of times, the XML parser claims the DTD is invalid. Here
> is an example:
>
>  com.caucho.xml.XmlParseException:
> http://aspectwerkz.codehaus.org/dtd/aspectwerkz_2_0.dtd:1:
> expected '<' at end of file
>          at com.caucho.xml.XmlParser.error(XmlParser.java:2831)
>          at
> com.caucho.xml.XmlParser.parseDoctypeDecl(XmlParser.java:573)
>          at
> com.caucho.xml.XmlParser.parseDoctype(XmlParser.java:496)
>          at
> com.caucho.xml.XmlParser.parseNode(XmlParser.java:386)
>          at
> com.caucho.xml.XmlParser.parseInt(XmlParser.java:240)
>          at
> com.caucho.xml.AbstractParser.parse(AbstractParser.java:633)
>          at org.dom4j.io.SAXReader.read(SAXReader.java:339)
>          at org.dom4j.io.SAXReader.read(SAXReader.java:261)
>          at
> org.codehaus.aspectwerkz.definition.XmlParser.createDocument(XmlParser.java:229)
>  ...
>
>  For long I believed this was a problem with the XML parser, but I have
> today discovered that this may rather be a bug within AspectWerkz in
> combination with online weaving and a dynamic class loader.
>
>  The DTD is located within the AW jar file by a static member in
> org.codehaus.aspectwerkz.definition.XmlParser, namely
> DTD_STREAM. This (as the name indicates...) is a stream. I believe the
> problem occurs because when the stream has been read once, it cannot be read
> again. When the web application is reloaded, the classes need to be
> re-weaved by AspectWerkz and AspectWerkz tries to parse aop.xml again. It
> then uses the same stream, since the AW jar is in the bootclasspath rather
> than the application classpath, and therefore the DTD cannot be read.
>
>  The obvious solution - which seem to work so far - is NOT to store the
> stream as a static member. Instead we store the URL and instantiate a new
> stream for every use. Below you will find a patch for this (I could e-mail
> this as a file).
>
>  What do you guys think? Is my analysis correct, or is this in fact an XML
> parser issue?
>
>
>  Index:
> src/main/org/codehaus/aspectwerkz/definition/XmlParser.java
> ===================================================================
>  RCS file:
> /home/projects/aspectwerkz/scm/aspectwerkz4/src/main/org/codehaus/aspectwerkz/definition/XmlParser.java,v
>  retrieving revision 1.6
>  diff -u -r1.6 XmlParser.java
>  ---
> src/main/org/codehaus/aspectwerkz/definition/XmlParser.java
>  15 Dec 2004 23:09:06 -0000      1.6
>  +++
> src/main/org/codehaus/aspectwerkz/definition/XmlParser.java
>  11 Nov 2005 10:59:24 -0000
>  @@ -47,7 +47,7 @@
>       /**
>        * A handler to the DTD stream so that we are only using one file
> descriptor
>        */
>  -    private final static InputStream DTD_STREAM =
> XmlParser.class.getResourceAsStream("/aspectwerkz2.dtd");
>  +    private final static URL DTD_URL =
> XmlParser.class.getResource("/aspectwerkz2.dtd");
>
>       /**
>        * The timestamp, holding the last time that the definition was
> parsed.
>  @@ -267,13 +267,15 @@
>           EntityResolver resolver = new EntityResolver() {
>               public InputSource resolveEntity(String publicId, String
> systemId) {
>                   if (publicId.equals(DTD_PUBLIC_ID) ||
> publicId.equals(DTD_PUBLIC_ID_ALIAS)) {
>  -                    InputStream in = DTD_STREAM;
>  -                    if (in == null) {
>  -                        System.err.println("AspectWerkz - WARN - could not
> open DTD");
>  -                        return new InputSource();
>  -                    } else {
>  -                        return new InputSource(in);
>  +                    try {
>  +                        InputStream in = DTD_URL.openStream();
>  +                        if (in != null)
>  +                            return new InputSource(in);
>                       }
>  +                    catch(IOException ioex ) {
>  +                    }
>  +                    System.err.println("AspectWerkz - WARN - could not
> open DTD");
>  +                    return new InputSource(); // avoid null pointer
> exception
>                   } else {
>                       System.err.println(
>                               "AspectWerkz - WARN - deprecated DTD "
>
>
>
>
>
>    Mattias Jiderhamn


--
Jonas Bonér
Terracotta, Inc.

http://www.terracottatech.com
http://blogs.codehaus.org/people/jboner/