A JAXP (Java API for XML Processing) developer primarily works with Java applications to process and manipulate XML data. They use the JAXP framework to parse XML documents, transform XML data using XSLT, and validate XML data against XML schema or DTD. They handle tasks like reading, writing and manipulating XML data, converting it into other formats, or extracting useful information. Additionally, they troubleshoot and resolve any issues related to XML data processing. Their role also involves staying updated with the latest trends in XML technologies and integrating them into existing systems to enhance functionality and efficiency.