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Tomcat , problem with libraries order

 
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I develop my application with FOP (Apache's formatter) on Oracle's JDeveloper 9i - there everything works OK.
But when I deploy application (through war file) to Tomcat 4.0.3, problems begin.
By this simple code I load XML file and change its encoding:
Document document;
XMLDocument xdoc;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating(false);
DocumentBuilder builder = dbf.newDocumentBuilder();
document = builder.parse(new File("report.xml"));
xdoc = (XMLDocument) document; // ERROR ON TOMCAT
String se = xdoc.getEncoding();
xdoc.setEncoding("WINDOWS-1250");
...
The marked line generates error "ClassCastException".
Both Document and XMLDocument are from the library XMLPARSERV2.JAR, which is loaded before every library FOP 0.20.3 (uses avalon-framework-4.0.jar, batik.jar, logkit-1.0.jar ,
xalan-2.0.0.jar, xerces.jar)
But the class with same name (with different beahavior) - Document.class is
also stored in batik.jar, xalan-2.0.0.jar and xerces.jar.
I think that Tomcat somewhat mixes the libraries order and takes Document.class from one of the FOP libraries instead from xmlparserv2.jar.
I am still rather new to this. Do I need to have set Classpath or something else installed, even if the application is run via web-browser ? (Now I have Tomcat and browser on one PC)
Does somebody see the solution to this ? Thanks.
 
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Tomcat maintains about 5 different sets of classpaths internally. They have a pretty good set of documentation on what they are and how they're used at the jakarta.apache.org/tomcat site.
One reason WHY they've devoted a lot of effort to that is because serious problems happened when Tomcat needed one version of an XML library for its own internal purposes, but webapps needed another(s), so they sat down and figured out a set of rules that (more or less) makes everyone happy.
 
Jiri Nejedly
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Thanks, I found out that Tomcat has its own XML parsing done by xerces.jar stored in \common\lib directory and every work with Document class goes primarily through this library. Either I must replace this library with other parser (xmlparserv2.jar, which however doesn't conform to Sun's JAXP standard ) or I must not use non-standard classes like XMLDocument.
 
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That's a strange sort of occurence. As I understand Tomcat classloaders... if you put xerces.jar version 1.0 (I'm taking that as example) into the WEB-INF/lib directory of your web application, then for that particular web application, version 1.0 of xerces is used, even though up in common/lib there might be a version 2.0 of xerces. And Tomcat will still use the one it knows about (the 2.0 one).

There should be no conflicts between jars used by your application and jars used by Tomcat, as long as they are kept in their proper places.
 
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In a Tomcat 4.0.6 project I'm working on, the servlet seemed to use the xerces.jar in common.lib instead of the one in the applications lib. However, there is a not near the bottom of the release memo that says

--------------------------
Tomcat 4.0 and XML Parsers:
--------------------------
As described above, Tomcat 4.0 makes an XML parser (and many other standard
APIs) available to web applications. This parser is also used internally
to parse web.xml files and the server.xml configuration file. If you wish,
you may replace the "xerces.jar" file in "common/lib" with another XML parser,
as long as it is compatible with the JAXP/1.1 APIs.

Replacing common/lib/xerces.jar with the one we needed seems to be working for us.
 
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