DataIntegrityViolationException保持一对多关系

Question

Boot,Jpa and hibernate to persist a one-many relation between venues and events.

The error i'm retrieving is

org.h2.jdbc.JdbcSQLException: NULL not allowed for column "VENUE_LOCATION"; SQL statement:
insert into event (id, date, description, media_ref, num_ratings, performer, performer_media, title, total_rating) values (null, ?, ?, ?, ?, ?, ?, ?, ?) [23502-192]

I've tried saving the parent(Venue) class first and exclusively but that produces the same error.

Venue

public class Venue
{
    @Id
    private String name;

    @Id
    private String location;

    @OneToOne(mappedBy = "venue",cascade = CascadeType.ALL)
    @JoinColumn(name="id")
    private VenueUser venueUser;

    private String mediaRef;

    private int rating;

    @OneToMany(fetch=FetchType.LAZY,mappedBy = "venue",cascade = CascadeType.ALL)
    private Set<Event> events;
    //Constructors getters and setters below

Event

@Entity
public class Event 
{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private long id;

private String title;
private String description;
private String performer;
private String[] performerMedia;
private Calendar[] date;

@Transient
private double avgRating;

private int numRatings;
private int totalRating;

private String mediaRef;

@MapsId("name")
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumns({
        @JoinColumn(name="Venue_name",referencedColumnName = "name"),
        @JoinColumn(name="venue_location",referencedColumnName = "location")
})
private Venue venue;
 //Constructors getters and setters below

Controller

@RequestMapping(value = "/event",method=RequestMethod.POST)
public ResponseEntity addEvent(@RequestBody Event event)
{
    Authentication auth = SecurityContextHolder.getContext().getAuthentication();
    String name = auth.getName(); //get logged in username
    Venue venue = userVenueRepository.findByEmail(name).getVenue();

    event.setVenue(venue);
    venue.addEvent(event);

    if(eventRepository.saveAndFlush(event).equals(event)&&venueRepository.saveAndFlush(venue).equals(venue))
    {
        return new ResponseEntity(HttpStatus.CREATED);
    }
    else
    {
        return new ResponseEntity(HttpStatus.CONFLICT);
    }

}

Answer 1

insert into event (id, date, description, media_ref, num_ratings, performer, performer_media, title, total_rating) values (null, ?, ?, ?, ?, ?, ?, ?, ?)

You need to set id to your Event entity. Better use @GeneratedValue annotation with AUTO , like here https://github.com/spring-projects/spring-data-jpa/blob/master/src/main/java/org/springframework/data/jpa/domain/AbstractPersistable.java

or use class AbstractPersistable as parent entity.

Answer 2

Error says that location field of Venue entity is null which cannot be as it is primary key.

You have two options for persisting Event object.

1. First persist Venue [Parent] Entity and then Persist as many Event [Child] entities as you want.Set venue field in event entity. You need to save Parent entity only once.
2. If you want to persist both parent and child at once, you can specify cascade = CascadeType.PERSIST in Event Entity and then save child entity.

Answer 3

好的，所以我设法解决了这个问题，事后我不应该盲目地按照教程进行操作，也不知道@MapsId做了什么，所以我删除了它，一切都开始起作用了。这引起了将不胜感激的问题。

Answer 4

You can try this too.

this way you don't need to add parent entry inside child object.

Remove mappedBy form Venue entity

Then add below code inside the Venue entity before Set<Event>

@JoinColumns({
        @JoinColumn(name="Venue_name",referencedColumnName = "name"),
        @JoinColumn(name="venue_location",referencedColumnName = "location")
})

Remove @JoinColumns and @MapsId from Event entity

Then you don't need to write

event.setVenue(venue);

Hope it helps.