Unmarshaling fields with underscores results in exception when fields serialized as attributes instead of tags.

The attached program recreates an exception when reading back in the field XStreamBug.Bug._underscore field.

Exception in thread "main" com.thoughtworks.xstream.converters.ConversionException: null
---- Debugging information ----
message : null
cause-exception : java.lang.NumberFormatException
cause-message : null
class : XStreamBug$Bug
required-type : XStreamBug$Bug
line number : 1
-------------------------------
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:63)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:45)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:46)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:117)
at com.thoughtworks.xstream.core.ReferenceByIdMarshallingStrategy.unmarshal(ReferenceByIdMarshallingStrategy.java:14)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:832)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:819)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:767)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:759)
at XStreamBug.main(XStreamBug.java:14)
Caused by: java.lang.NumberFormatException: null
at java.lang.Long.parseLong(Long.java:372)
at java.lang.Long.valueOf(Long.java:518)
at com.thoughtworks.xstream.converters.basic.LongConverter.fromString(LongConverter.java:16)
at com.thoughtworks.xstream.converters.SingleValueConverterWrapper.fromString(SingleValueConverterWrapper.java:31)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:142)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:121)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:56)
... 9 more

The line "xs.useAttributeFor(long.class)" is the key to recreating this exception. When left out, it works fine. Stepping through the code shows that the attribute name doesn't get escaped before asking the reader for the attribute. For example, in XppReader, the getAttribute(String name) method should probably be something like the following:

public String getAttribute(String name)

Essentially, any field that has an underscore that is written out as an attribute doesn't get deserialized properly without some type of exception.