Your questions are not very clear, but if I understand you correctly, you are trying to generate fields dynamically, meaning that you don't know the name, type or length of the field until run-time.
One way to do this would be to define your ActionForm as type org.apache.struts.validator.LazyValidatorForm. This is a form bean provided by Struts that does not require you to define getters or setters for properties or to define them ahead of time in the struts-config.xml file. If you use this class as the ActionForm, any <html:text> fields that you define with any property name will be populated into the ActionForm bean when the form is submitted. All of the properties will be of type String, but if you have another field telling you what the correct type is, you can then convert to the correct type.