JPA Eclipselink错误：“字段'target_id'没有默认值”

Question

我会尽量简短客观。我使用的是JPA Eclipselink2.5.2。在用MySQL脚本创建数据库之后，我正在尝试填充它。编译给了我以下错误：

线程“main”javax.Persistence.persistenceException：异常[EclipseLink-4002]（Eclipse Persistence Services-2.5.2.V20140319-9AD6ABD):org.Eclipse.Persistence.exceptions.DatabaseException内部异常：java.sql.sqlexception：字段'target_id'没有默认值错误代码：1364调用：INSERT INTARG(32_bit_arch,IP,Name,Operating_system)值（？,？,？,？）绑定=>[true，127.0.0.1，Intel i7 2.6 Ghz+8 GB，CentOS 6.5 32位]

我已经在SO和Google上搜索过了，但是即使我发现了类似的情况（例如这个），解决方案似乎也不起作用（删除@JoinColumn(nullable=false)或应用@OneTomany(orphanRemoval=true)等的not null约束）。有关资料如下：

1、MySQL表创建脚本：

-- -----------------------------------------------------
-- Table `fault_injector`.`Target`
-- -----------------------------------------------------
DROP TABLE IF EXISTS `fault_injector`.`Target` ;

CREATE TABLE IF NOT EXISTS `fault_injector`.`Target` (
  `Target_id` INT NOT NULL AUTO_INCREMENT,
  `Name` VARCHAR(30) NOT NULL,
  `32_bit_arch` TINYINT(1) NOT NULL,
  `IP` VARCHAR(15) NOT NULL,
  `Operating_system` VARCHAR(30) NOT NULL,
  PRIMARY KEY (`Target_id`),
  UNIQUE INDEX `idTarget_UNIQUE` (`Target_id` ASC),
  UNIQUE INDEX `IP_UNIQUE` (`IP` ASC))
ENGINE = InnoDB;

-- -----------------------------------------------------
-- Table `fault_injector`.`Experiment`
-- -----------------------------------------------------
DROP TABLE IF EXISTS `fault_injector`.`Experiment` ;

CREATE TABLE IF NOT EXISTS `fault_injector`.`Experiment` (
  `Exp_id` INT NOT NULL AUTO_INCREMENT,
  `Creator_id` INT NOT NULL,
  `Target_id` INT NOT NULL,
  `Name` VARCHAR(30) NOT NULL,
  `Creation_date` TIMESTAMP NOT NULL,
  `Injection_date` TIMESTAMP NULL,
  `Description` VARCHAR(300) NOT NULL,
  PRIMARY KEY (`Exp_id`),
  UNIQUE INDEX `Experiment_id_UNIQUE` (`Exp_id` ASC),
  INDEX `Target_id_idx` (`Target_id` ASC),
  INDEX `User_id_idx` (`Creator_id` ASC),
  CONSTRAINT `Experiment_User_id_fk`
    FOREIGN KEY (`Creator_id`)
    REFERENCES `fault_injector`.`User` (`User_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `Experiment_Target_id_fk`
    FOREIGN KEY (`Target_id`)
    REFERENCES `fault_injector`.`Target` (`Target_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

2.目标实体：

@Entity
@NamedQuery(name="Target.findAll", query="SELECT t FROM Target t")
public class Target implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="Target_id")
    private int target_id;

    [...]

    //bi-directional many-to-one association to Experiment
    @OneToMany(mappedBy="target")
    private List<Experiment> experiments;

    [...]

    public List<Experiment> getExperiments()
    {
        if(this.experiments==null)
            this.experiments = new ArrayList<Experiment>();

        return this.experiments;
    }

    public Experiment addExperiment(Experiment experiment) {
        getExperiments().add(experiment);
        experiment.setTarget(this);

        return experiment;
    }

@Entity
@NamedQuery(name="Experiment.findAll", query="SELECT e FROM Experiment    e")
public class Experiment implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    @Column(name="Exp_id")
    private int exp_id;

    [...]

    //bi-directional many-to-one association to Target
    @ManyToOne(cascade = CascadeType.PERSIST)
    @JoinColumn(name="Target_id")
    private Target target;

    [...]

    public void setTarget(Target target) {
        this.target = target;
    }

4.代码

尽管编译器说该错误发生在实体管理器调用flush时(em.flush()；)，但我知道其他行与该错误有关，因为如果我注释它，错误就会消失:target.addexperiment（experiment）；（请注意target和experiment都是同名实体的实例--如果需要，我可以发布更多代码，但目前我试图使问题不长）。所以问题似乎在于目标和实验之间的双向关联，但除此之外，我还被这个错误所困扰。

Answer 1

查看数据库中的表定义，例如。

describe target

我想，它不同于create table语句，您已经在问题中显示了。特别是列target_id的定义可能不会显示为auto_increment。

根据target_id的定义，您可以使用

alter table target modify column target_id int not null auto_increment;