Initializing Beans from the Request
If the value attribute is omitted from a jsp:setProperty element, the JSP container looks for a (form) parameter with the same name as the property, and sets the property using the value of that parameter.
For example, if the a JavaBean class UserBean has a property userName, this property could be initialized as follows:
<jsp:useBean id=“user” class=“UserBean”>
<jsp:setProperty name=“user” property=“userName”>
</jsp:useBean>
The value of the userName property will be taken from the value of a form parameter called userName.