Struts uses
Apache Commons BeanUtils to perform this function. When a form is submitted, the Struts RequestProcessor examines each of the parameters sent with the request, looks for an appropriate setter method on the ActionForm bean and calls it, passing the appropriate data. For example, if a parameter named "userName" is sent with the request, Struts will look for a method named "setUserName" on the ActionForm and call that method passing the parameter value.
[ July 26, 2008: Message edited by: Merrill Higginson ]