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From el...@apache.org
Subject cvs commit: xml-xerces/java/docs faq-general.xml
Date Fri, 20 Feb 2004 16:38:01 GMT
elena       2004/02/20 08:38:01

  Modified:    java/docs faq-general.xml
  Add FAQ on Xerces serializers and classloaders
  Revision  Changes    Path
  1.40      +56 -0     xml-xerces/java/docs/faq-general.xml
  Index: faq-general.xml
  RCS file: /home/cvs/xml-xerces/java/docs/faq-general.xml,v
  retrieving revision 1.39
  retrieving revision 1.40
  diff -u -r1.39 -r1.40
  --- faq-general.xml	18 Feb 2004 22:27:06 -0000	1.39
  +++ faq-general.xml	20 Feb 2004 16:38:01 -0000	1.40
  @@ -38,6 +38,62 @@
  + <faq title="ClassCastException using Xerces">
  +   <q>Why do I get ClassCastException when I use Xerces and WebSphere Application
Server (WAS)?
  + </q>
  + <a>
  +    <p>
  +Xerces uses the <code>ObjectFactory</code> class to load some classes dynamically,
e.g. the parser configuration. The <code>ObjectFactory</code> finds the specified
implementation class by querying the system property, reading <code>META-INF/services/factoryId</code>
file or using a fallback classname. After the implementation is found, the <code>ObjectFactory</code>
tries to load the file using the context classloader and if it is null, the <code>ObjectFactory</code>
uses system classloader. 
  +If you run Xerces in the environment, such as WAS, that has multiple classloaders you might
get ClassCastExceptions thrown from Xerces because different classloaders might get involved
in loading Xerces classes. For example, ClassCastExceptions may occur when utility EAR classes
that use Xerces load Xerces classes from WAR modules. 
  +We suggest you read <jump href="http://www-106.ibm.com/developerworks/websphere/library/techarticles/0310_searle/searle.html">"Avoiding
ClassCastExceptions..."</jump> article which explains a workaround for this problem.

  +Also you might want to read <jump href="http://www-106.ibm.com/developerworks/websphere/library/techarticles/0112_deboer/deboer.html">"J2EE
Class Loading Demystified"</jump> article that explains how multiple classloaders work
in WAS.
  +    </p>
  +  </a>
  + </faq>
  + <faq title="Xerces HTML, XHTML, and XML Serializers">
  +   <q>What can I use instead of Xerces HTML, XHTML, or XML serializers?
  + </q>
  + <a>
  +If you want to achieve interoperability, you should not be using Xerces serialization code
  +Instead, the <jump href="http://java.sun.com/xml/jaxp/index.jsp">JAXP</jump>
Transformer API should be used to serialize HTML, XHTML, and SAX. The <jump href="http://www.w3.org/DOM/DOMTR">DOM</jump>
Level 3 Load and Save API (or JAXP Transformer API) should be used to serialize DOM.
  +    <p>Using <jump href="http://java.sun.com/xml/jaxp/index.jsp">JAXP</jump>
you can serialize HTML and XHTML as follows:</p>
  +// Create an "identity" transformer - copies input to output
  +Transformer t = TransformerFactory.newInstance().newTransformer();
  +// for "XHTML" serialization, use the output method "xml"
  +// and set publicId as shown
  +t.setOutputProperty(OutputKeys.METHOD, "xml");
  +                    "-//W3C//DTD XHTML 1.0 Transitional//EN");
  +               "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd");
  +// For "HTML" serialization, use
  +t.setOutputProperty(OutputKeys.METHOD, "html");
  +// Serialize DOM tree
  +t.transform(new DOMSource(doc), new StreamResult(System.out));
  +You can find more details about the future of Xerces serializers in the <jump href="http://marc.theaimsgroup.com/?l=xalan-dev&amp;m=107593381313807&amp;w=2">archives</jump>.
  +<note>The HTML and XHTML serializers (<code>org.apache.xml.serialize</code>)
have been <code>deprecated</code> in Xerces 2.6.2 release. We might deprecate
<code>XMLSerializer</code> in the future release.</note>
  +  </a>
  + </faq>
    <faq title="Obtaining smaller jars">
      <q>I don&apos;t need all the features Xerces provides, but I&apos;m
      running in an environment where space is at a premium.  Is there

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