org.springframework.web.HttpMediaTypeNotSupportedException - spring-boot

Question

when i am trying to get values by id ..i got error like this in postman
{
"timestamp": 1547708533031,
"status": 500,
"error": "Internal Server Error",
"exception":"org.springframework.http.converter.HttpMessageNotWritableException",
"message": "Could not write JSON: 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); nested exception is com.fasterxml.jackson.databind.JsonMappingException: 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) (through reference chain: com.Cetegory.Entites.ArtistRegister[\"subcetgory\"]->com.Cetegory.Entites.SubCetegory_$$_jvst706_1[\"handler\"])",
"path": "/getartist/2"
}
this is contoller for get data by id
#RestController
public class RegisterController {
#Autowired
ArtistService artser;
#PostMapping(value="/addArtist",produces="application/json")
#ResponseBody public ArtistRegister addArtist(#RequestBody ArtistRegister artist) {
ArtistRegister artRegister = null;
try {
artRegister = artser.addArtist(artist);
} catch (Exception e) {
e.printStackTrace();
}
return artRegister;
}
#RequestMapping(value="/getartist/{artist_id}",method=RequestMethod.GET,produces="application/json")
#ResponseBody public ArtistRegister getArtistDetails(#PathVariable ("artist_id") int artist_id ,HttpServletRequest request,
HttpServletResponse response) throws Exception{
return artser.getArtistDetails(artist_id);
}
#RequestMapping(value="/delete/{artist_id}",method=RequestMethod.DELETE,produces="application/json")
public void deleteById(#PathVariable (value="artist_id") int artist_id,HttpServletRequest request,
HttpServletResponse response) throws Exception{
artser.deleteById(artist_id);
}
#RequestMapping(value = "/updateartist", method = RequestMethod.PUT, produces = "application/json")
public ArtistRegister updateArtist(#RequestBody ArtistRegister artreg, HttpServletRequest request, HttpServletResponse response)
throws Exception
{
return artser.updateArtist(artreg);
}
this is service
#Service
#Transactional
public class ArtistService {
#Autowired
private ArtistRepository artrep;
#Autowired
private RegisterDAO artdao;
public ArtistRegister addArtist(ArtistRegister artreg) {
ArtistRegister artReg = null;
try {
artReg = artrep.save(artreg);
} catch (Exception e) {
e.printStackTrace();
}
return artReg;
}
public ArtistRegister getArtistDetails(int artist_id) {
return artdao.getArtistDetails(artist_id);
}
public void deleteById(int artist_id) {
artdao.deleteById(artist_id);
}
public ArtistRegister updateArtist(ArtistRegister artreg) {
return artdao.updateArtist(artreg);
}
}
this is DAO
#Repository
#Transactional
public class RegisterDAO {
private static final Logger logger = LoggerFactory.getLogger(SubCetegoryDAO.class);
#Autowired
SessionFactory sessionFactory;
#Autowired
EntityManager entitymanager;
public ArtistRegister getArtistDetails(int artist_id) {
try
{
String hql = "FROM ArtistRegister a where a.artist_id=?";
return (ArtistRegister) entitymanager.createQuery(hql).setParameter(1, artist_id).getSingleResult();
}
catch (EmptyResultDataAccessException e)
{
return null;
}
catch (Exception e)
{
logger.error("Exception in getUser"+ e.getMessage());
return null;
}
}

Answer 1

Remove #JsonManagedReference annotation and update fetch type to LAZY, by following way:
#OneToOne(targetEntity = SubCetegory.class, cascade = CascadeType.MERGE,fetch=FetchType.LAZY)
#JoinColumn(name = "sub_cetegory_id")
What are fetch types Lazy and Eager?
The EAGER strategy is a requirement on the persistence provider runtime that data must be eagerly fetched. The LAZY strategy is a hint to the persistence provider runtime that data should be fetched lazily when it is first accessed.
REFERENCES
Official documentation fetch type