java - Returning object-parameter in Web-Flow -

i have following files:

webflow-context.xml

... <bean id="user" class="com.bla-bla.datamodel.user" scope="prototype" /> ... 

user.java

public class user implements serializable {     private static final long serialversionuid = 1l;     private integer id;     private string name;     private address address = new address();     //setters , getters } 

adduser.jspx

... <form:form commandname="user">         <form:hidden path="id" />                     <form:input path="name"/>                     <form:input path="address.street"/>           <div class="buttons">             <div class="button">                 <button type="submit" name="_eventid_canceluser">                     <fmt:message key="button.cancel" />                 </button>                 <button type="submit" name="_eventid_usernext">                     <fmt:message key="button.next" />                 </button>             </div>         </div> </form:form> ... 

adduser.xml

    <on-start>         <set name="flowscope.user" value="user" />     </on-start>      <view-state id="adduser" view="adduser">         <transition on="canceluser" to="canceluser"/>         <transition on="usernext" to="usernext">             <set name="user.name" value="requestparameters.name"/>             <set name="user.address.street" value="requestparameters.address.street"/>         </transition>     </view-state> ... 

the problem works correctly has error:

org.springframework.web.util.nestedservletexception: request processing failed; nested exception org.springframework.webflow.execution.actionexecutionexception: exception thrown executing [annotatedaction@741dbf43 targetaction = [setaction@4cf80343 name = user.address.street, value = requestparameters.address.street], attributes = map[[empty]]] in state ' adduser ' of flow ' adduser ' -- action execution attributes 'map[[empty]]' org.springframework.webflow.execution.actionexecutionexception: exception thrown executing [annotatedaction@741dbf43 targetaction = [setaction@4cf80343 name = user.address.street, value = requestparameters.address.street], attributes = map[[empty]]] in state ' adduser ' of flow ' adduser ' -- action execution attributes 'map[[empty]]' org.springframework.binding.expression.evaluationexception: elexception occurred getting value expression 'requestparameters.address.street' on context [class org.springframework.webflow.engine.impl.requestcontrolcontextimpl] org.springframework.expression.spel.spelevaluationexception: el1007e:(pos 0): field or property 'street' cannot found on null 

if field «user» object, error. job data entered on page , save in bean user (flowscope.user) last step process them.

how right?

upd:i found problem, after <form:input path="address.street"/> address = null. why?

i think problem here: value="requestparameters.address.street"

requestparameters can contain strings , expect object of type address

simply pass street ...&name=foo&street=bar... in url , receive requestparameters.street