HiLo发电机策略不起作用

Question

我是hibernate的新手。我想要做的是使用@CollectionIdto为我的Address类生成一个标识符。我已经使用了Collection接口。但是，当我使用@GenericGenerator并将策略设置为hilo时，它会抛出异常。这是我的代码：

@Entity
@Table(name = "USER_DETAILS")
public class UserDetails {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int userId;
    private String userName;

    @ElementCollection
    @JoinTable(name="USER_ADDRESS",
        joinColumns=@JoinColumn(name="USER_ID")
    )

    @GenericGenerator(name = "hilo-gen", strategy = "hilo")
    @CollectionId(columns = { @Column(name="ADDRESS_ID") }, generator = "hilo-gen", type = @Type(type="long"))
    private Collection<Address> address = new ArrayList<Address>();

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Collection<Address> getAddress() {
        return address;
    }

    public void setAddress(List<Address> address) {
        this.address = address;
    }
}

我得到以下异常：

Exception in thread "main" org.hibernate.MappingException: Could not instantiate id generator [entity-name=null]
    at org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory.createIdentifierGenerator(DefaultIdentifierGeneratorFactory.java:121)
    at org.hibernate.mapping.SimpleValue.createIdentifierGenerator(SimpleValue.java:259)
    at org.hibernate.persister.collection.AbstractCollectionPersister.<init>(AbstractCollectionPersister.java:429)
    at org.hibernate.persister.collection.BasicCollectionPersister.<init>(BasicCollectionPersister.java:57)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.hibernate.persister.internal.PersisterFactoryImpl.createCollectionPersister(PersisterFactoryImpl.java:152)
    at org.hibernate.persister.internal.PersisterFactoryImpl.createCollectionPersister(PersisterFactoryImpl.java:140)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:408)
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:708)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:724)
    at com.hbt.HibernateTest.main(HibernateTest.java:35)
Caused by: java.lang.UnsupportedOperationException: Support for 'hilo' generator has been removed
    at org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory.getIdentifierGeneratorClass(DefaultIdentifierGeneratorFactory.java:132)
    at org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory.createIdentifierGenerator(DefaultIdentifierGeneratorFactory.java:112)
    ... 14 more

我正在使用最新的休眠。我该怎么办？

Answer 1

Hilo不再受支持，这应该可行

@GenericGenerator(name="sequence-gen",strategy="sequence")

Answer 2

如果我们使用mysql，最好使用增量策略的@GenericGenerator。

1. 序列 - 这种策略由Oracle支持Postgresql。
2. 增量 - 这种策略由MySql支持。

   @ElementCollection
   @JoinTable(name="USER_ADDRESS", joinColumns=@JoinColumn(name="USER_ID"))
   @GenericGenerator(name = "increment-gen", strategy = "increment")
   @CollectionId(columns = { @Column(name="ADDRESS_ID") }, generator = "increment-gen", type = @Type(type="long"))
   private Collection<Address> listOfAddress = new ArrayList<>();

当我使用MySql的序列策略时，我遇到了一个问题，即我的ADDRESS_ID没有正确递增。

Answer 3

'hilo'生成器的支持已被删除。有关其他信息，此链接将为您提供已弃用的列表。

要克服这个问题，您可以简单地使用序列生成器。这将解决您的问题。

@Entity
@Table(name = "USER_DETAILS")
public class UserDetails {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int userId;
    private String userName;

    @ElementCollection
    @JoinTable(name="USER_ADDRESS",
        joinColumns=@JoinColumn(name="USER_ID")
    )

    @GenericGenerator(name = "sequence-gen", strategy = "sequence")
    @CollectionId(columns = { @Column(name="ADDRESS_ID") }, generator = "sequence-gen", type = @Type(type="long"))
    private Collection<Address> address = new ArrayList<Address>();

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Collection<Address> getAddress() {
        return address;
    }

    public void setAddress(List<Address> address) {
        this.address = address;
    }
}

Answer 4

您必须从Hi / Lo策略中选择一个：

• SequenceHiLoGenerator：用序列支持Hi
• MultipleHiLoPerTableGenerator：用桌子支持你

为了尽可能接近您的教程，我只需在代码中将“hilo”更改为“seqhilo”。

Answer 5

我建议您尝试以下任何一种解决方案，它将解决您的问题。它符合Hibernate 5.2.X中提供的规范。

信息来源-https://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html

解决方案1 ​​ -

 @GenericGenerator(name = "product_generator",strategy = "org.hibernate.id.enhanced.SequenceStyleGenerator")
 @CollectionId(columns = { @Column(name="ADDRESS_ID") }, generator = "product_generator", type = @Type(type="long"))*

解决方案2 -

*@GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "product_generator")
 @CollectionId(columns = { @Column(name="ADDRESS_ID") }, generator = "product_generator", type = @Type(type="long"))*

如果它对您有帮助，请告诉我。

Answer 6

仅供参考，MYSQL支持序列策略，但表名不应包含连字符' - '（在@GenericGenerator（name）中提供的名称可能会在mysql中创建序列表时导致DDL异常。

Answer 7

这适用于PostgreSQL上的应用程序。虽然我没有对它进行测试，但它应该适用于所有数据库。请注意，increment-gen不是序列使用。

@ElementCollection
    @JoinTable( name = "user_address", joinColumns = @JoinColumn( name = "user_id"))
    @GenericGenerator(name="increment-gen",strategy="increment")
    @CollectionId( columns = { @Column( name ="address_id") }, generator ="increment-gen", type =@Type( type ="long"))
    private Collection<Address> listOfAddresses = new ArrayList<Address>();