spring MVC LazyInitialisationException - spring-mvc

Question

we are working on springMVC java config app. I am facing a problem every time when i trying to view child object properties but getting lazyinitialisationexception no session error. this i am getting on ajax calls also. I know that eager fetching is one solution and Hibernate.initailize(child) is another. But what is the standard way to resolve this?
My entities are like this
import java.io.Serializable;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
#Entity
#Table(name = "COUNTRY_DETAILS")
public class Country implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private Long id;
private String name;
private Set<State> states;
#Id
#GeneratedValue
#Column(name = "ID", length = 20, nullable = false)
public Long getId() {
return id;
}
public void set Id(Long id) {
this.id = id;
}
#Column(name = "NAME", length = 20, nullable = false)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Country() {
super();
// TODO Auto-generated constructor stub
}
public Country(String name) {
super();
this.name = name;
}
#OneToMany(fetch = FetchType.LAZY, mappedBy = "countryId")
public Set<State> getStates() {
return states;
}
public void setUnits(Set<State> states) {
this.states = states;
}
}
States entity
#Entity
#Table(name = "State_DETAILS")
public class State implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue
#Column(name = "State_ID", length = 20, nullable = false)
private Long StateId;
#Column(name = "State_NAME", length = 20, nullable = false)
private String StateName;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "Country_ID", nullable = false, //
foreignKey = #ForeignKey(name = "Country_DETAIL_State_FK") )
private Country countryId;
Public Long getStateId() {
return StateId;
}
public void setStateId(Long StateId) {
this.StateId = StateId;
}
public String getStateName() {
return StateName;
}
public void setStateName(String StateName) {
this.StateName = StateName;
}
public Country getCountryId() {
return countryId;
}
public void setCmdId(Country countryId) {
this.countryId = countryId;
}
public State(Long StateId) {
super();
this.StateId = StateId;
}
public State() {
super();
// TODO Auto-generated constructor stub
}
}
My Controller
This is my controler
#RequestMapping(value = "/findStatesByCountry", method = RequestMethod.GET)
public #ResponseBody List<State> findAllStateByCountryId() {
Country c=new Country();
c.setId((long) 1);
List<State> states=stateService.getStatesByCommand(c);
return units;
}
Error I am getting is
org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: could not initialize proxy - no Session
I want to show in view like country.state.stateId ,state.country.name e.t.c .
How to resolve this type of situation?
Eager is the not the solution i want to use

Answer 1

Found the answer finally.OpenEMInViewFilter is the solution..I tried the following and working fine...
<filter-name>openSessionInViewFilter</filter-name>
<filter-class>
org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter
</filter-class>
</filter>
<filter-mapping>
<filter-name>openSessionInViewFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
I have used interceptor also..
<mvc:interceptors> <mvc:interceptor> <mvc:mapping path="/**"/> <mvc:exclude-mapping
path="/resources/**"/>
<bean class="org.springframework.orm.jpa.support.OpenEntityManagerInViewInterceptor"
/>
</mvc:interceptor>
</mvc:interceptors>
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
it is working fine now and able to fetch associations in views.Let me know if any cons in this type of usage...
Thanx