Question

我使用EJB 3.我有基类A，并且有依赖类B，C，D

@Entity
@Table(name = "A")
public class A implements Serializable {

    @OneToMany(cascade = CascadeType.ALL)
    private List<B> bs;

    @OneToMany(cascade = CascadeType.ALL)
    private List<C> cs;

    @OneToMany(cascade = CascadeType.ALL)
    private List<D> ds;

}

我有疑问。如何热切地加载所有表？我想使用em.find(A.class, id);

Answer 1

您必须使用OneToMany注释中的获取属性，以便：

@Entity
@Table(name = "A")
public class A implements Serializable {

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private List<B> bs;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private List<C> cs;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private List<D> ds;

}

Answer 2

我找到了问题的解决方案。

@Entity
@Table(name = "A")
public class A implements Serializable {

    @OneToMany(cascade = CascadeType.ALL)
    @Fetch(FetchMode.SUBSELECT)
    private List<B> bs;

    @OneToMany(cascade = CascadeType.ALL)
    @Fetch(FetchMode.SUBSELECT)
    private List<C> cs;

    @OneToMany(cascade = CascadeType.ALL)
    @Fetch(FetchMode.SUBSELECT)
    private List<D> ds;

}

解决方案是@Fetch（FetchMode.SUBSELECT）。有一篇关于

的好文章

Hibernate Fetching Strategies

EJB 3渴望加载

2 个答案: