Localizing XMLJava requires processing Java .properties files. JavaPM is used to generate XLIFF from /src folder.
Use a command like this to generate XLIFF:
/path-to-Javapm/createxliff.sh -srcLang en -tgtLang es -enc UTF-8 -reuse -2.0 -src /path-to-XMLJava/src -xliff yourXliffFile.xlf XMLJava .properties are encoded in UTF-8; translated versions must be generated using UTF-8 character set.
You can find XLIFF and TMX sample files for XMLJava's .properties in /i18n folder.