I have a SAR. One of the MBean attributes is a String (actually, for my real use-case the value is a Properties object, but due to JIRA AS7-5336, there are other problems, but let's just go with String attribute type, because the same problem I will describe happens with that type, too)

If the string value is longer than around 3650 characters the beginning of the string is stripped (I can't nail it down to a specific value, but its around that number, give or take 10 characters or so)

For example, if I have this in jboss-service.xml:

<attribute name="MyStrAttrib">
This is a really long string.
...[lots of characters here]...
It has more than 3650
characters in it.
</attribute>

What my MBean setter (setMyStrAttrib(String s)) will be passed is something like "aracters in it." The characters at index 0 through ~3650 are missing, I only have the parts after it.

In my real example, the reason why the string is so long is that its a Properties string with lots of name/value pairs. I ended up working around AS7-5336 but then I hit this issue.