It is used to give values to properties of beans that have been referenced beforehand.
<jsp:useBean id=”ABC”…/>
…
<jsp:setProperty name=”ABC” property=”myProperty”…
jsp:setproperty is executed even if a new bean is instantiated or existing bean is found.
By adding </jsp.useBean> at the end of the code, the condition for execution is inverted i.e. It is not executed if existing object was found and only if a new object was instantiated.