java - 关于使用 Hibernate 将对象映射到数据库

Question

大家好，我是 hibernate 新手。当我在堆栈溢出中浏览 hibernate 相关主题时，我发现了这个

Need clarification about mapping objects to database, annotations, and one to many relationships

读完解决方案后，我有点困惑，并开始构建确切的场景，以了解多对一背后的实际机制，其中我使用了 Oracle 11g 数据库。当我运行我的项目时，hibernate 会自动生成表和 FK 关系，但在插入数据时它面临这个问题(这是显而易见的)

WARN: HHH000437: Attempting to save one or more entities that have a non-nullable association with an unsaved transient entity. The unsaved transient entity must be saved in an operation prior to saving these dependent entities.
Unsaved transient entity: ([com.entity.Authorization#0])
Dependent entities: ([[com.entity.Job#1]])

WARN: HHH000437: Attempting to save one or more entities that have a non-nullable association with an unsaved transient entity. The unsaved transient entity must be saved in an operation prior to saving these dependent entities.
    Unsaved transient entity: ([com.entity.JobFilteration#0])
    Dependent entities: ([[com.entity.Job#1]])
    Non-nullable association(s): ([com.entity.Job.jobfilteration])

我所做的正是我提到的上述主题的解决方案，我正在发布我的实体类，请帮助我解决这个问题

类(class)作业

@Entity
@Table(name="JOB")
public class Job implements Serializable {
    @Id 
    @SequenceGenerator(name="person_seq", sequenceName="SEQ_PERSON",initialValue=1,allocationSize=1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE ,generator="person_seq")
    @Column(name="JOB_SERIAL")
    private int id;

    @Column(name="JOB_CATAGORY",nullable=false,length=200,unique=true)
    private String catagory;


    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn (name="JOB_AUTHID", nullable = false, updatable = false, insertable = false)
    private Authorization authorization;

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn (name="JOB_JOBFILTERID", nullable = false, updatable = false, insertable = false)
    private JobFilteration jobfilteration;

JobFilteration 类

@Entity
@Table(name="JOB_FILTERATION")
public class JobFilteration implements Serializable {
    @Id 
    @SequenceGenerator(name="person_seq", sequenceName="SEQ_PERSON",initialValue=1,allocationSize=1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE ,generator="person_seq")
    @Column(name="FILTER_SERIAL")
    private int id;

    @Column(name="FILTERNAME",nullable=false,length=200)
    private String filtername;

类授权

@Entity
@Table(name="AUTHORIZATION")
public class Authorization implements Serializable {
    @Id 
    @SequenceGenerator(name="person_seq", sequenceName="SEQ_PERSON",initialValue=1,allocationSize=1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE ,generator="person_seq")
    @Column(name="AUTH_ID")
    private int id;

    @Column(name="AUTHORISEDBY",nullable=false,length=200)
    private String authorisedby;

为了插入数据，我编写了一个方法public void insertToDB(Job job)(我对三个类使用了相同的序列以节省时间)，然后

JoBDao jobdao= new JoBDao();
Job job= null;
Authorization auth = null;
JobFilteration jfilter = null;

try{
job= new Job();

auth = new Authorization();
    auth.setAuthorisedby("SOMEPERSON");

jfilter = new JobFilteration();
    jfilter.setFiltername("JEE");

job.setCatagory("PERMANENT");
job.setAuthorization(auth);
job.setJobfilteration(jfilter);


jobdao.addPersonandCard(job);

我认为发生异常是因为数据先插入作业表，然后再插入其他表。请帮我找出我错过了什么？

Answer 1

首先尝试保存依赖实体(在您的情况下为授权)，然后尝试保存外部实体(作业)

session.save(Authorization's object);
session.save(Job's object)