Question

我在JPA实体经理面临一个非常奇怪的问题。我有两个实体 1）事件 2）国家

国家是主人，事件是ManyToOne的孩子。

Incident.java

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

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "incidentID")
    private Integer incidentID;

    @Column(name = "incidentTitle")
    private String incidentTitle;

    @ManyToOne
    @JoinColumn(name = "countryID")
    private Country country;

    @Transient
    @ManyToOne
    @JoinColumn(name = "countryID")
    public Country getCountry() {
        return country;
    }

    public void setCountry(Country country) {
        this.country = country;
    }

    // Getter and setters


}

Country.Java

@Entity
@Table(name="Country")
public class Country {
    @Id
    @Column(name="id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "name")
    private String name;

    @OneToMany(mappedBy = "country", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Incident> incident;


     @OneToMany
        @JoinColumn(
            name="countryID",nullable=false)
    public List<Incident> getIncident() {
        return incident;
    }

    public void setIncident(List<Incident> incident) {
        this.incident = incident;
    }
    //getter and setter

}

RepositoryImpl.java

@Repository
@Transactional
public class IncidentRepositoryImpl implements IncidentRepository{

    @PersistenceContext
    private EntityManager em;

    @Autowired
    public void setEntityManager(EntityManagerFactory sf) {
        this.em = sf.createEntityManager();
    }

    @Override
    public Incident addIncident(Incident incident) {
        try {           
            em.getTransaction().begin();
            em.persist(incident);
            em.getTransaction().commit();
            return incident;
        } catch (HibernateException e) {            
            return null;
        }
    }


    public Incident findById(int id) {
        Incident incident = null;
        incident = (Incident) em.find(Incident.class, id);      
        return incident;

    }

}

当我添加事件时，事件在事件表中成功添加了countryID，但是当我尝试获取同一事件时，国家/地区名称为空。但是，当我重新启动服务器或重新部署应用程序国家/地区名称时也会出现。希望JAP实体管理器存在缓存问题。我尝试在findById方法中使用em.refresh（incident），然后国家名称成功。但是这种刷新方法是非常昂贵的。

请提供一些替代解决方案，如何自动更新jpa缓存。

Answer 1

在EntityManager em上，添加

@PersistenceContext(type = PersistenceContextType.TRANSACTION)
private EntityManager em;

使用PersistenceContextType.TRANSACTION，Spring可以控制EntityManager

的生命周期

JPA无法获取更新的数据

1 个答案: