Details
Bug
Closed
Major
Description
Executing the following unit test against the svn trunk produces an assertion error and prints the json:
{"tree-map":
,"entry":{"string":["a","b"]}}
It seems the "entry" element should be part of the "tree-map" element, rather than at the top level
public void testTreeMap()
{ TreeMap map = new TreeMap(); map.put("a", "b"); XStream xstream = new XStream(new JettisonMappedXmlDriver()); String json = xstream.toXML(map); System.out.println(json); Object o = xstream.fromXML(json); assertEquals(map, o); }Issue Links
- is related to
-
XSTR-576
Remove <no-comparator/> tag from TreeMap and TreeSet output.
-
Activity
The problem is that TreeMapConverter is using an empty xml element to represent the lack of a value.
I don't think json has the same concept of a null object.
inserting:
context.convertAnother(true);
on line 75 fixes the problem, however it makes the xml look a bit more ugly (it was already pretty clearly a signal to the deserializer rather than a model of the serialized data though)
The alternative would be to not have any element to represent the lack of a comparator, and use the lack of the comparator node to signal a naturally ordered TreeMap, however I tried coding that up and it was starting to look extremely ugly.
That might just be my inexperience with the stream writer model thinger in use though.
Travis Dixon
added a comment - The problem is that TreeMapConverter is using an empty xml element to represent the lack of a value.
I don't think json has the same concept of a null object.
inserting:
context.convertAnother(true);
on line 75 fixes the problem, however it makes the xml look a bit more ugly (it was already pretty clearly a signal to the deserializer rather than a model of the serialized data though)
The alternative would be to not have any element to represent the lack of a comparator, and use the lack of the comparator node to signal a naturally ordered TreeMap, however I tried coding that up and it was starting to look extremely ugly.
That might just be my inexperience with the stream writer model thinger in use though. XStream writes anything that is necessary to recreate the object. The TreeMapConverter uses the first element to keep track of a comparator, otherwise it could not differentiate from the first element in the map. Please use Jettison 1.2, it has a better handling of empty elements.
Jörg Schaible
added a comment - XStream writes anything that is necessary to recreate the object. The TreeMapConverter uses the first element to keep track of a comparator, otherwise it could not differentiate from the first element in the map. Please use Jettison 1.2, it has a better handling of empty elements. While the problem is not really solvable in case a comparator is actually set, it works now at least without explicit comparator due to fixed issue XSTR-576. Available in HEAD.
Jörg Schaible
added a comment - While the problem is not really solvable in case a comparator is actually set, it works now at least without explicit comparator due to fixed issue XSTR-576 . Available in HEAD. 
com.thoughtworks.xstream.converters.collections.TreeMapConverter:73
a TreeMap with a comparator will be successfully serialized and de-serialized.
Seems like the problem is either in PathTrackingWriter or jettison itself.
For the moment two usable work-arounds exist:
1 - Ensure all TreeMap's being serialized have comparators
2 - Write our own TreeMapConverter to either set the comparator at serialization, or ignore null comparators (which requires changes to deserialization)