今天又深入了了解和测试了一下Hibernate cascade 和 inverse 。

Inverse

在Hibernate annotation 中inverse 默认值是"true" 当配置了mappedBy="…"时就相当于inverse="false"了。

Cascade

CascadeType类中有这样几个常量，ALL、PERSIST、MERGE、REFRESH、REMOVE 。

让代码说话吧：

@Entity

@Table(name = "Users")

public class User implements java.io.Serializable {

    private String id;

    private Rose rose;

    public User() {

    }

    @Id

    @Column(name = "Id", unique = true, nullable = false, insertable = true, updatable = true, length = 5)

    public String getId() {

        return this.id;

    }

    public void setId(String id) {

        this.id = id;

    }

    @ManyToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE }, fetch = FetchType.LAZY)

    @JoinColumn(name = "Roseid", unique = false, nullable = false, insertable = true, updatable = true)

    public Rose getRose() {

        return this.rose;

    }

    public void setRose(Rose rose) {

        this.rose = rose;

    }

}

@Entity

@Table(name = "Rose")

public class Rose implements java.io.Serializable {

    private String id;

    private Set<User> users = new HashSet<User>(0);

    public Rose() {

    }

    @Id

    @Column(name = "Id", unique = true, nullable = false, insertable = true, updatable = true, length = 3)

    public String getId() {

        return this.id;

    }

    public void setId(String id) {

        this.id = id;

    }

    @OneToMany(cascade = { CascadeType.ALL }, fetch = FetchType.EAGER )

    @JoinColumn(name="RoseId")

    public Set<User> getUsers() {

        return this.users;

    }

    public void setUsers(Set<User> userses) {

        this.users = userses;

    }

    public void addUser(User user) {

        user.setRose(this);

        users.add(user);

    }

当在user类中配置成cascade = { CascadeType.PERSIST, CascadeType.MERGE } 时，更新和删除两个级联时:

Hibernate: select user_.Id, user_.Enabledel as Enabledel1_, user_.Name as Name1_, user_.Password as Password1_, user_.Roseid as Roseid1_ from ERP.dbo.Users user_ where user_.Id=?

Hibernate: select rose_.Id, rose_.Enabledel as Enabledel0_, rose_.Name as Name0_, rose_.Parent as Parent0_ from ERP.dbo.Rose rose_ where rose_.Id=?

Hibernate: delete from ERP.dbo.Users where Id=?

可以正常删除！但是代码要这样写：

         User user =new User("adm");

         user.setRose(new Rose("adm"));    //这句不加就不能删除，提示错误。除非数据库不加级联限制

        userDao.delete(user);

当在user类中配置成cascade = { CascadeType.ALL } or cascade={} 时，无法删除。

更新时也类似于这种情况，注意rose类中的addUser(User user)方法。

再有fetch = FetchType.EAGER。在这里不是延时加载，如果设置成LAZY,在取得数据时怎么做好呢？看其他论坛的方法各有好处也有不好的地方，在找一个更方法。。。