Review Request and Testing Question on: Remove unnecessary field and methods from NoSuchMechanismException

[Sebastian Sickelmann]

Hi,

while making some change for using exception-chaining on 
RuntimeException in more cases, i found that 
javax.xml.crypto.NoSuchMechnismException had a private cause field that 
isn't necessary since throwable can handle it. But just removing isn't 
that simple as Alan pointed out[1].
First of all i thought just changing the serialversionUID was the right 
solution, but Alan disagreed and i actually think that too. Unfortunatly 
Alan doen't had the time to explain it in detail, but i think that we 
must search for a solution that doen't break backward serialization 
compatability.

I created a webrev for my suggested change here:
http://oss-patches.24.eu/openjdk8/NoSuchMechanismException/REBASED_ON_8018d541a7b2/

The problem i have is that i think we should add some test for this. But 
got no real clue how to do it right. I tested it manually with the 
source here[2] and the files in here[3].

The files are created with an openjdk7 build(Unfortunatly i think with 
an quite old private build) and with an openjdk8(with my patches to 
NoSuchMechanismException). I tested it manually with my openjdk 7 and 8 
build and in both cases the serialized objects could be loaded correctly 
in all cases.

What is the best way to test this automatically. I thought about 
checking if the newly created openjdk8 serialization is binary equal to 
the jdk7 output, but it isn't because of some unavoidable changes (ex. 
jdk8 has the custom-serialization-bit)

-- Sebastian

[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2011-August/007462.html
[2] 
http://oss-patches.24.eu/openjdk8/NoSuchMechanismException/SeriallizeTest.java
[3] http://oss-patches.24.eu/openjdk8/NoSuchMechanismException/