[FIXED] LazyInitializationException encountered when using load instead of get with Hibernate

Issue

I am using JPA, Hibernate and Spring MVC. In the controller class all the methods works greatly. When I test them in the web browser the public String getModuleFormation(long id) method, that returns an object, and it gives me the following error:

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

as a root cause, but yesterday I tried it, and it worked without problem in the localhost:45045/GestionModules/detail/xx URL.

What could cause this problem?

My detail.jsp:

<c:if test="${!empty detailModule}">

${detailModule.idModule}
${detailModule.libModule}
</c:if>

POJO Class + JPA :

@Entity
@Table(name="ModuleFormation")
public class ModuleFormation {

private long idModule;
private String libModule;

public ModuleFormation() {
    // TODO Auto-generated constructor stub
}

public ModuleFormation(String libModule) {
    this.libModule = libModule;
}

@Id
@GeneratedValue(strategy = GenerationType.AUTO, generator = "seqModule")
@SequenceGenerator(name="seqModule", sequenceName = "seqModuleFormation")
@Column(name="idModule")
public long getIdModule() {
    return this.idModule;
}

public void setIdModule(long idModule) {
    this.idModule = idModule;
}

@Column(name="libModule", nullable=false, length = 100)
public String getLibModule() {
    return this.libModule;
}

public void setLibModule(String libModule) {
    this.libModule = libModule;
}

}

DAO Class :

@Repository
public class ModuleFormationDAOImpl implements ModuleFormationDAO {

@Autowired
private SessionFactory sessionFactory;


public void ajouterModuleFormation(ModuleFormation module) {
    sessionFactory.getCurrentSession().save(module);
}

public void supprimerModuleFormation(long idModule) {
    ModuleFormation module = (ModuleFormation) sessionFactory.getCurrentSession().load(ModuleFormation.class, idModule);
    if(module != null)
        sessionFactory.getCurrentSession().delete(module);
}

public List<ModuleFormation> listModuleFormation() {
    
    return sessionFactory.getCurrentSession().createQuery("from ModuleFormation")
            .list();
    
}

public ModuleFormation getModuleFormation(long idModule) {
     return (ModuleFormation) sessionFactory.getCurrentSession().load(ModuleFormation.class, idModule);
}

public void majModuleFormation(ModuleFormation module) {
    sessionFactory.getCurrentSession().merge(module);
}

}

Service Class :

@Service
public class ModuleFormationServiceImpl implements ModuleFormationService {

@Autowired
private ModuleFormationDAO moduleDao;

@Transactional
public void ajouterModuleFormation(ModuleFormation module) {
    moduleDao.ajouterModuleFormation(module);
}

@Transactional
public void supprimerModuleFormation(long idModule) {
    moduleDao.supprimerModuleFormation(idModule);
}

@Transactional
public List<ModuleFormation> listModuleFormation() {
    return moduleDao.listModuleFormation();
}

@Transactional
public ModuleFormation getModuleFormation(long idModule) {
    return moduleDao.getModuleFormation(idModule);
}

@Transactional
public void majModuleFormation(ModuleFormation module) {
    moduleDao.majModuleFormation(module);
}
}

Controller Class :

@Controller
public class ModuleFormationController {

@Autowired
private ModuleFormationService moduleService;

@RequestMapping("/module")
public String listModulesFormations(Map<String, Object> map) {
    
    map.put("module", new ModuleFormation());
    map.put("moduleList", moduleService.listModuleFormation());
    
    return "module";
}

@RequestMapping(value = "/ajouter", method = RequestMethod.POST )
public String ajouterModuleFormation(@ModelAttribute("module")
ModuleFormation module,BindingResult result) {
    
    moduleService.ajouterModuleFormation(module);
    
    return "redirect:/module";
}


@RequestMapping(value = "/supprimer/{idModule}")
public String supprimerModuleFormation(@PathVariable("idModule")
long idModule) {
    moduleService.supprimerModuleFormation(idModule);
    
    return "redirect:/module";
}


@RequestMapping(value= "/detail/{idModule}")
public String getModuleFormation(@PathVariable("idModule")
long idModule,Map<String, Object> map) {
    map.put("detailModule", moduleService.getModuleFormation(idModule));
    return "/detail";
}

    
@RequestMapping(value= "/detail/modifier", method = RequestMethod.POST )
public String majModuleFormation(@ModelAttribute("detailModule")
ModuleFormation module, BindingResult result) {
    moduleService.majModuleFormation(module);
    return "detail/{idModule}";
}

}

Solution

The Javadoc on the Hibernate Session#load(Class, Serializable) method says:

Return the persistent instance of the given entity class with the given identifier, assuming that the instance exists. This method might return a proxied instance that is initialized on-demand, when a non-identifier method is accessed.

When you access a property on the object in your JSP the session which loaded the object has been closed.

Use Session#get(Class, Serializable) to ensure that you don't load a proxy.

Answered By - Alex Barnes
Answer Checked By - Terry (JavaFixing Volunteer)