Usualy, java source files for XML binding are generated using some XML schema or DTD for expected data format.
In this case, proposal is to define XML schema, for example like this:
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://test.org/test/Employee">
<xsd:element name="employee">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="name" type="xsd:string" />
<xsd:element name="age" type="xsd:integer" />
<xsd:element name="salary" type="xsd:double" />
</xsd:sequence>
</xsd:complexType>
</xsd:element>
This schema.xsd can be used as input to the number of generators like JAXB (xjc command) or Castor, as shown here
Generator output is configurable, and new sources should be easy to integrate to existing project, or compile and load. This topic is discussed here