When customer tries to load a PDF with a PNG file they get a linkage error

Customer gets a linkage error when they try to load a PDF with a PNG.

The java spec relating to these issues is here:

http://java.sun.com/docs/books/jvms/second_edition/html/ConstantPool.doc.html

The customer is seeing this error due to a loading constraint. Here is the explanation of class loading constraints:

A loading constraint is violated if, and only if, all the following four
conditions hold:

There exists a loader L such that L has been recorded by the Java
virtual machine as an initiating loader of a class C named N.

There exists a loader L' such that L' has been recorded by the Java
virtual machine as an initiating loader of a class C' named N.

The equivalence relation defined by the (transitive closure of the) set
of imposed constraints implies N L = N L'.

C != C '.
***

I 'think' that the idea is that if you have two different class loaders
(L and L'), and each loads a class (L loads C and L' loads C') with the
same name (N), loading constraints will be violated if C and C' are not
the same class.

So to bring this back around in relation to issue CSP-19301:

The customer unpacked these jars that ship with confluence:
saxon-6.5.3-patched.jar
ss_css2-0.9.3.jar
xml-apis-1.0.b2.jar
xmlParserAPIs-2.2.1.jar

There are incompatible versions of NodeClass included.

you'll see that they differ in size (1630 vs 1597), indicating that they are different versions of the same class.

rw-rr- 1 ubuntu ubuntu 1630 2000-10-09 18:02 ./saxon-6.5.3-patched.jar/org/w3c/dom/Node.class
rw-rr- 1 ubuntu ubuntu 1630 2003-01-19 23:14 ./ss_css2-0.9.3.jar/org/w3c/dom/Node.class
rw-rr- 1 ubuntu ubuntu 1597 2002-12-01 11:57 ./xml-apis-1.0.b2.jar/org/w3c/dom/Node.class
rw-rr- 1 ubuntu ubuntu 1597 2002-11-11 18:24 ./xmlParserAPIs-2.2.1.jar/org/w3c/dom/Node.class

The following error is thrown

com.atlassian.core.exception.InfrastructureException: java.lang.LinkageError: Class org/w3c/dom/Node violates loader constraints

So this leads back to the point:

if you have two different class loaders
(L and L'), and each loads a class (L loads C and L' loads C') with the
same name (N), loading constraints will be violated if C and C' are not
the same class.