What is the proper way for fetching or ignoring lazy loaded objects using hibernate and spring - spring

Question

I am using spring MVC + hibernate + jackson.
Spring version : 4.3.x
Hibernate version : 4.3.x
I want to create two API- one fetching BeanB objects as well while one not fetching BeanB object. I am using fetchtype.lazy for the same.
I have following beans:
#Entity
class BeanA
{
#Id
int id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "BeanB_id")
private BeanB beanB;
//getters and setters
}
#Entity
class BeanB
{
#Id
int i;
//getters and setters
}
In my controller I have two methods: (Removing service layer to make question small. In my service layer class, I have #Transactional)
#RequestMapping(value = "/beanA/{id}" , method=RequestMethod.GET)
public ResponseEntity<BeanA> findDetailedBeanAById(#PathVariable("id") int id )
{
// to return beanA object with beanB
BeanA beanA = beanADao.findDetailedBeanAById(id);
return new ResponseEntity<BeanA>(beanA, HttpStatus.OK);
}
#RequestMapping(value = "/beanA/{id}" , method=RequestMethod.GET)
public ResponseEntity<BeanA> findNonDetailedBeanAById(#PathVariable("id") int id )
{
// to return beanA object without beanB
BeanA beanA = beanADao.findNonDetailedBeanAById(id);
return new ResponseEntity<BeanA>(beanA, HttpStatus.OK);
}
In My Dao
public BeanA findDetailedBeanAById(long id) {
BeanA beanA = (BeanA) getSession().get(BeanA.class, id);
Hibernate.initialize(beanA.getBeanB())
return beanA;
}
public BeanA findNonDetailedBeanAById(long id) {
BeanA beanA = (BeanA) getSession().get(BeanA.class, id);
return beanA;
}
When I am hitting findNonDetailedBeanAById controller method, I am getting error as :
org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: could not initialize proxy - no Session
When I am hitting findNonDetailedBeanAById controller method, I am getting error as :
org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS)`
What changes are needed to be done?

Answer 1

For the detailed findBy method you can build a custom query and fetching the beanB inside of the query, like getSession().createQuery("SELECT a FROM beanA a LEFT JOIN FETCH a.beanB WHERE a.id == :id")
For the lazy findBy method I think you need to add the #Transactional(readonly=true) at the controller level, because you are trying to use the beanA after getting it with the service which was annotated as transactional. I think it tries to fetch the beanB from the database but the hibernate session might already be closed.
I was not able to tryout any of my suggestions because I'm only at phone.