休眠：“字段 'id' 没有默认值”

Question

我正面临我认为 Hibernate 的一个简单问题，但无法解决（无法访问 Hibernate 论坛当然无济于事）。

我有一个简单的课程我想坚持，但不断得到：

 SEVERE: Field 'id' doesn't have a default value
Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not insert: [hibtest.model.Mensagem]
    at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:103)
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:91)
    [ a bunch more ]
Caused by: java.sql.SQLException: Field 'id' doesn't have a default value
    [ a bunch more ]

持久类的相关代码是：

 package hibtest.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Mensagem  {
    protected Long id;

    protected Mensagem() { }

    @Id
    @GeneratedValue
    public Long getId() {
        return id;
}

    public Mensagem setId(Long id) {
        this.id = id;
        return this;
    }
}

实际运行的代码很简单：

 SessionFactory factory = new AnnotationConfiguration()
    .configure()
    .buildSessionFactory();

{
    Session session = factory.openSession();
    Transaction tx = session.beginTransaction();

    Mensagem msg = new Mensagem("YARR!");

    session.save(msg);

    tx.commit();
    session.close();
}

我在 GeneratedValue 注释中尝试了一些“策略”，但它似乎不起作用。初始化 id 也无济于事！ （例如 Long id = 20L ）。

任何人都可以解释一下吗？

编辑 2： 确认：搞乱 @GeneratedValue(strategy = GenerationType.XXX) 不能解决它

已 解决： 重新创建数据库解决了问题

原文由 André Chalella 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

有时，即使在执行 SchemaUpdate 之后，对模型或 ORM 所做的更改也可能无法准确反映在数据库中。

如果错误实际上似乎缺乏合理的解释，请尝试重新创建数据库（或至少创建一个新数据库）并使用 SchemaExport 它。

原文由 André Chalella 发布，翻译遵循 CC BY-SA 2.5 许可协议

Answer 2

如果你想让 MySQL 自动生成主键，那么你必须在创建表时告诉它。您不必在 Oracle 中执行此操作。

在主键上，您必须包括 AUTO_INCREMENT 。请参见下面的示例。

 CREATE TABLE `supplier`
(
  `ID` int(11) NOT NULL **AUTO_INCREMENT**,
  `FIRSTNAME` varchar(60) NOT NULL,
  `SECONDNAME` varchar(100) NOT NULL,
  `PROPERTYNUM` varchar(50) DEFAULT NULL,
  `STREETNAME` varchar(50) DEFAULT NULL,
  `CITY` varchar(50) DEFAULT NULL,
  `COUNTY` varchar(50) DEFAULT NULL,
  `COUNTRY` varchar(50) DEFAULT NULL,
  `POSTCODE` varchar(50) DEFAULT NULL,
  `HomePHONENUM` bigint(20) DEFAULT NULL,
  `WorkPHONENUM` bigint(20) DEFAULT NULL,
  `MobilePHONENUM` bigint(20) DEFAULT NULL,
  `EMAIL` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`ID`)
)

ENGINE=InnoDB DEFAULT CHARSET=latin1;

这是实体

package com.keyes.jpa;

import java.io.Serializable;
import javax.persistence.*;
import java.math.BigInteger;

/**
 * The persistent class for the parkingsupplier database table.
 *
 */
@Entity
@Table(name = "supplier")
public class supplier implements Serializable
{
  private static final long serialVersionUID = 1L;

  @Id
  **@GeneratedValue(strategy = GenerationType.IDENTITY)**
  @Column(name = "ID")
  private long id;

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

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

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

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

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

  @Column(name = "HomePHONENUM")
  private BigInteger homePHONENUM;

  @Column(name = "MobilePHONENUM")
  private BigInteger mobilePHONENUM;

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

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

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

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

  @Column(name = "WorkPHONENUM")
  private BigInteger workPHONENUM;

  public supplier()
  {
  }

  public long getId()
  {
    return this.id;
  }

  public void setId(long id)
  {
    this.id = id;
  }

  public String getCity()
  {
    return this.city;
  }

  public void setCity(String city)
  {
    this.city = city;
  }

  public String getCountry()
  {
    return this.country;
  }

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

  public String getCounty()
  {
    return this.county;
  }

  public void setCounty(String county)
  {
    this.county = county;
  }

  public String getEmail()
  {
    return this.email;
  }

  public void setEmail(String email)
  {
    this.email = email;
  }

  public String getFirstname()
  {
    return this.firstname;
  }

  public void setFirstname(String firstname)
  {
    this.firstname = firstname;
  }

  public BigInteger getHomePHONENUM()
  {
    return this.homePHONENUM;
  }

  public void setHomePHONENUM(BigInteger homePHONENUM)
  {
    this.homePHONENUM = homePHONENUM;
  }

  public BigInteger getMobilePHONENUM()
  {
    return this.mobilePHONENUM;
  }

  public void setMobilePHONENUM(BigInteger mobilePHONENUM)
  {
    this.mobilePHONENUM = mobilePHONENUM;
  }

  public String getPostcode()
  {
    return this.postcode;
  }

  public void setPostcode(String postcode)
  {
    this.postcode = postcode;
  }

  public String getPropertynum()
  {
    return this.propertynum;
  }

  public void setPropertynum(String propertynum)
  {
    this.propertynum = propertynum;
  }

  public String getSecondname()
  {
    return this.secondname;
  }

  public void setSecondname(String secondname)
  {
    this.secondname = secondname;
  }

  public String getStreetname()
  {
    return this.streetname;
  }

  public void setStreetname(String streetname)
  {
    this.streetname = streetname;
  }

  public BigInteger getWorkPHONENUM()
  {
    return this.workPHONENUM;
  }

  public void setWorkPHONENUM(BigInteger workPHONENUM)
  {
    this.workPHONENUM = workPHONENUM;
  }

}

原文由 Greg Keyes 发布，翻译遵循 CC BY-SA 3.0 许可协议