java 如何在 Hibernate 中设置只读列？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/14626341/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to set read-only columns in Hibernate?
提问by cloudy_weather
I don't know how to force read-only columns in Hibernate.
我不知道如何在 Hibernate 中强制只读列。
I would like to set idgroup as read only column. Even if I set insertable=falseand updatable=false, in the hibernate SQL I can read:
我想将 idgroup 设置为只读列。即使我设置了insertable=falseand updatable=false，在休眠 SQL 中我也可以阅读：
Hibernate: insert into groups (description, name, account_idaccount, idgroup) values (?, ?, ?, ?)
but I would like to obtain:
但我想获得：
insert into groups (description, name, account_idaccount) values (?, ?, ?)
Here are my classes:
这是我的课程：
@Entity
@Table(name = "groups")
public class Group implements java.io.Serializable {
private static final long serialVersionUID = -2948610975819234753L;
private GroupId id;
private Account account;
private String name;
private String description;
@EmbeddedId
@AttributeOverrides({@AttributeOverride(name = "idgroup", column = @Column(name = "idgroup", insertable = false)),
@AttributeOverride(name = "accountIdaccount", column = @Column(name = "account_idaccount", nullable = false))})
public GroupId getId() {
return id;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "account_idaccount", nullable = false, insertable = false, updatable = false)
public Account getAccount() {
return account;
}
@Column(name = "description", length = 512)
public String getDescription() {
return description;
}
@Column(name = "name", nullable = false, length = 128)
public String getName() {
return name;
}
..
}
@Embeddable
public class GroupId implements java.io.Serializable {
private int idgroup;
private int accountIdaccount;
@Column(name = "idgroup", insertable= false, updatable= false)
public int getIdgroup() {
return this.idgroup;
}
@Column(name = "account_idaccount", nullable = false)
public int getAccountIdaccount() {
return this.accountIdaccount;
}
..
}
I would like to have a read only column for idgroup because I can exploit the id auto-generation of the DBMS, I do not want to use the key auto-generation in Hibernate because it is not cluster-safe.
我想为 idgroup 设置一个只读列，因为我可以利用 DBMS 的 id 自动生成，我不想在 Hibernate 中使用密钥自动生成，因为它不是集群安全的。
采纳答案by cloudy_weather
The solution is using wrapper classes, such as Integer, not primitivetypes like int.
When Hibernate will get a null pointer it will delegate the generation of the id to the DBMS.
解决方案是使用包装类，例如Integer，而不是像int. 当 Hibernate 得到一个空指针时，它将把 id 的生成委托给 DBMS。
回答by Bob Flannigon
I think you can mark an @Columnannotation as updatable=false
我认为您可以将@Column注释标记为updatable=false
回答by J. Jerez
Easy: @Column(insertable = false, updatable = false)
简单：@Column（可插入 = 假，可更新 = 假）
回答by jDub9
I was able to achieve this by using 2 DAO objects. I know it may not be preferred, but I didn't see another way around it. Setting the field to insertable=falseand updatable=falsedo not remove the columns from the insert SQL so Postgres will not invoke the defaultaction to populate those column values.
我能够通过使用 2 个 DAO 对象来实现这一点。我知道它可能不是首选，但我没有看到其他方法。将字段设置为insertable=false并且updatable=false不从插入 SQL 中删除列，因此 Postgres 不会调用default操作来填充这些列值。
// GroupWrite
@Entity
@Table(name = "group")
public class GroupWrite {
@Id
@Column(name = "account")
private Account account;
@Column(name = "name")
private String name;
@Column(name = "description")
private String description;
/* Getters and Setters */
}
--
——
// GroupRead
@Entity
@Table(name = "group")
public class GroupRead {
@EmbeddedId
@Column(name = "id")
private GroupId id;
@Column(name = "account")
private Account account;
@Column(name = "name")
private String name;
@Column(name = "description")
private String description;
/* Getters and Setters */
}
Then you need to use the GroupReadwhen using selectqueries and GroupWritewhen doing insertor updatequeries.
然后你需要使用GroupReadwhen using selectqueries 和GroupWritewhen doinsert或update查询。
If you want to use attributes from both in a common way you can implement an interface that describes the overlapping fields.
如果您想以通用方式使用两者的属性，您可以实现一个描述重叠字段的接口。
public interface Group {
Account getAccount();
void setAccount(Account account);
}
public class GroupWrite implements Group {...}
public class GroupRead implements Group {...}
Hope this helps.
希望这可以帮助。
回答by Rakesh
@ReadOnlyProperty annotation will help you in this case.
在这种情况下，@ReadOnlyProperty 注释将为您提供帮助。
