LazyInitializationException Spring 和 Hibernate

Question

我得到这个异常嵌套异常是org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.ibm.ro.model.Location.subLocations, could not initialize proxy - no Session.

我在访问集合时确实知道，事务已经关闭，这就是代码抛出此异常的原因。这是我的示例代码

@Entity
@Table(name="location")
public class Location extends BaseEntity {

    private static final long serialVersionUID = 1L;

    private String name;
    private List<Location> subLocations;
    private Location location;

    @Column(name="name")
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "location")
    public List<Location> getSubLocations() {
        return subLocations;
    }
    public void setSubLocations(List<Location> subLocations) {
        this.subLocations = subLocations;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    public Location getLocation() {
        return location;
    }
    public void setLocation(Location location) {
        this.location = location;
    }

    @Override
    public String toString() {
        return "Location [name=" + name + ", subLocations=" + subLocations
            + "]";
    }

}

这是我的 DAO：

@Repository("locationDao")
public class LocationDao implements ILocationDao{

    @Autowired
    private SessionFactory sessionFactory;

    @Override
    public List<Location> getAll() {
        Session sess = getSession();
        return sess.createCriteria(Location.class).setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY).list();
    }
}

那么这是我的服务：

@Service("locationService")
@Transactional
public class LocationService implements ILocationService{

    @Autowired
    ILocationDao dao;

    @Override
    public List<Location> getAll() {
        return dao.getAll();
    }
}

这是抛出异常的控制器：

@Controller
public class BaseController {

    @Autowired
    ILocationService service;

    private static final String VIEW_INDEX = "index";
    private final static org.slf4j.Logger logger =    LoggerFactory.getLogger(BaseController.class);

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String location(ModelMap model) {        
    logger.debug(service.getAll().toString());
        return VIEW_INDEX;
    }
}

在不使用 OpenSessionInViewFilter 的情况下如何解决问题？

Answer 1

你可以在你的服务中迭代你的位置（你仍然有你的事务）并在元素上调用Hibernate.initialize，强制初始化持久集合。

    @Override
    public List<Location> getAll() {
        List<Location> locations = dao.getAll();
        for (Location location : locations ) { 
          Hibernate.intialize(location.getSubLocations())
        }
        return locations;
    }