What's the purpose of defining redirections for JRE-Classes in JBoss AS 7?

[cberger]

Hey guys,

it would be nice if someboy could tell me why JBoss defines these redirections:

javax.xml.parsers.SAXParserFactory = __redirected.__SAXParserFactory
javax.xml.stream.XMLEventFactory = __redirected.__XMLEventFactory
javax.xml.stream.XMLInputFactory = __redirected.__XMLInputFactory
javax.xml.stream.XMLOutputFactory = __redirected.__XMLOutputFactory
javax.xml.transform.TransformerFactory = __redirected.__TransformerFactory
javax.xml.validation.SchemaFactory:http://www.w3.org/2001/XMLSchema = __redirected.__SchemaFactory
javax.xml.xpath.XPathFactory:http://java.sun.com/jaxp/xpath/dom = __redirected.__XPathFactory

I've found a lot of articles about ClassNotFoundExceptions related to these redirected classes. I'm familiar with the fundamental principle of the jboss modular class loading environment but I do not understand why I get these exceptions occasionally.

As I understand, there is a problem with the implementaions when they load classes dynamically (e.g. Class.forName()). Because in this case, the wrong CL could be used (eg. TCCL). But why is this only sometimes the case?

I would be very pleased if somebody can give a comprehensive description of how jboss-modules, these redirections and the wrong way of using CL relates to each other to get this result:

03:48:28,161 ERROR [stderr] Caused by: java.lang.ClassNotFoundException: __redirected.__XMLInputFactory
03:48:28,162 ERROR [stderr]     at java.lang.Class.forName(Class.java:139)
03:48:28,163 ERROR [stderr]     at javax.xml.stream.FactoryFinder.newInstance(Unknown Source)
03:48:28,171 ERROR [stderr]     at javax.xml.stream.FactoryFinder.find(Unknown Source)
03:48:28,171 ERROR [stderr]     at javax.xml.stream.FactoryFinder.find(Unknown Source)

Thanks in advance

Christian

[cberger]

up, because of the spam bots

[nickarls]

J.G has an answer in

https://community.jboss.org/thread/171177

(although I'm not sure if there has been changes since then)

[cberger]

Hi Nicklas,

thx for sharing the link, unfortunately I already now that discussion. The exception occured likely in the OSGi env but after switching to JBoss 7.2.0 everything is fine. That's great but I want to understand why it's working now. Since deployments in JBoss 7 are all modules they have the similar isolated behaviour like OSGi-Bundles. IMHO: the reason for these exceptions must be the same for modules and bundles.

Are there any further information about this topic?

Thanks in advance

Cheers

Christian