This is coming with the bundled jaxb of jdk1.6.0_21.

For this reason storing references to marshallers is not a good idea if you last time marshalled some huge files.

The class is for testing purposes in the attachment. The first argument is package name the second is a unicode xml file. If it is not unicode change the encoding in inputstreamreader. Use big file about 100 MB to see the problem nice way. I attached a screenshot about the heapdump (stopped by debugger) after the line "Trying to release writer locally - nothing happened. Small change is there because string is collected".

I would recommend to do some similar test for unmarshaller and a bytearrayinputstream for example. Is it holding the reference or not?

Example test output:

Test started. Package:biz.i2z.model.content.jaxb, file: c:\2\cucc4, filesize (UNICODE FILE) in mb: 148
MAX : 1450 mb
FREE : 12 mb
TOTAL: 15 mb
Object tree constructed.
MAX : 1450 mb
FREE : 310 mb
TOTAL: 535 mb
State after serialization
MAX : 1450 mb
FREE : 821 mb
TOTAL: 1450 mb
Trying to release writer locally - nothing happened. Small change is there because string is collected.
MAX : 1450 mb
FREE : 969 mb
TOTAL: 1450 mb
Reusing the marshaller released memory
MAX : 1450 mb
FREE : 1225 mb
TOTAL: 1450 mb
Serializing again to get a new proof
MAX : 1450 mb
FREE : 821 mb
TOTAL: 1450 mb
The memory is freed because the buffer that is held by marshaller/xmlserializer/xmloutput is truncated.
MAX : 1450 mb
FREE : 1226 mb
TOTAL: 1450 mb