We Keep Coding

In the Entity class there are two references to the same field in the database

I am studying a training project - working with databases.
Here is a class describing the entity
#Entity
#Table(name = "pricelists", schema = "inventories")
public class PriceList {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "id_inventory", insertable = false, updatable = false)
private Long idInventory;
#ManyToOne
#JoinColumn(name = "id_inventory", nullable = false)
private Inventory inventory;
private Integer price;
}
And there are two variables that refer to the same "id_inventory" field in the database table. Is it possible to do this? Is this not a mistake?

You should leave that
#Entity
#Table(name = "pricelists", schema = "inventories")
public class PriceList {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne
#JoinColumn(name = "id_inventory", nullable = false)
private Inventory inventory;
private Integer price;
}
I hope that will work.

One table has two same joins in another table

I have one table called image and another table called duplicate. There are two OneToMany relations are associated.
I am not quite sure whether below implementation is the right approach for that. Moreover whether we require that second private List<DuplicateEntity> duplicateEntities2; ?
ImageEntity:
#Entity
#Table(name = "image")
public class ImageEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "filename")
private String fileName;
#OneToMany(mappedBy = "imageEntity1")
private List<DuplicateEntity> duplicateEntities1;
#OneToMany(mappedBy = "imageEntity2")
private List<DuplicateEntity> duplicateEntities2;
}
DuplicateEntity:
#Entity
#Table(name = "duplicate")
public class DuplicateEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne
#JoinColumn(name = "image_a_id")
private ImageEntity imageEntity1;
#ManyToOne
#JoinColumn(name = "image_b_id")
private ImageEntity imageEntity2;
}

Hibernate not fetching subentity if distinct not present

We have the following domain:
Members and Channels.
Member - equivalent of a user.
#Entity
#Table(name = "member")
public class Member {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "first_name")
private String firstName;
}
Channel - Will group blog posts by topic.
#Entity
#Table(name = "channel")
public class Channel {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long id;
#Column(name = "name")
private String name;
}
The members can be assigned to channels thus becoming members in the channel. So we have the ChannelMember entity since we don't always want to retrieve both ends of the relationship.
#Entity
#Table(name = "channel_member")
public class ChannelMember {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToOne
#JoinColumn(name = "channel_id", nullable = false)
private Channel channel;
#OneToOne
#JoinColumn(name = "member_id", nullable = false)
private Member member;
}
We use Spring Data JPA and MySQL for our persistance(Spring Boot 1.5.3 Release).
Why is the distinct mandatory in the JPQL query for Hibernate to be able to fetch any records in the following case?
Repository code example as follows:
#Repository
public interface MemberRepository extends JpaRepository<Member, Long> {
#Query("select cm.member from ChannelMember cm")
List<Member> getNotWorking(); // empty List will be returned
#Query("select distinct cm.member from ChannelMember cm")
List<Member> getWorking();
}

How remove some fields of referenced entity from criteria query in hibernate

Suppose we have entity A that contains a list of entities with type B (with lazy initialization).
Entity B has one BLOB field and some other, that doesn't contain much data.
How can I, using hibernate criteria query, get entity A with it's fields and each A-entity with list of Bs, but every B-entity without the BLOB field ?
Also, I do not want to extract As and iterate them to get Bs. (I now, how to use 'Projections' to extract just Bs with required fields).
Here is some code sample:
A-entity:
#Entity
#Table(name = "A")
public class A implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
#OneToMany(mappedBy = "order", fetch = FetchType.LAZY)
#Cascade(CascadeType.ALL)
private List<B> list = new LinkedList<>();
}
B-entity:
#Entity
#Table(name = "B")
public class B implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
#Column(name = "data", nullable = false)
#Lob
private byte[] data;
#ManyToOne(targetEntity = A.class, fetch = FetchType.EAGER)
#JoinColumn(name = "A_id", nullable = false)
private A a;
}

Hiibernate: #OrderColumn in #OneToMany causes an UPDATE after INSERT

I have the following POJOs for my db schema.
#Entity
#Table(name = "Quotes")
public class QuoteRequest
{
public QuoteRequest(){}
#Id
#Column(name = "quote_request_id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long QuoteRequestId;
#OneToMany(mappedBy = "quoteRequest", cascade = CascadeType.ALL)
#OrderColumn(name = "accidents_id")
private Accidents[] accidents;
// Getters and setters
}
#Entity
#Table(name = "Accidents")
public class Accidents
{
public Accidents()
{
}
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "accidents_id")
private long AccidentId;
#Column(name = "amount", nullable = false)
private Float amount;
#ManyToOne(optional = false, cascade = CascadeType.ALL)
#JoinColumn(name = "quote_request_id", nullable = false)
private QuoteRequest quoteRequest;
// Getters and setters
}
Because I'm using an array to store Accidents[] Hibernate is requiring me to add #OrderColumn. Adding this causes an update to be generated after insert that zeros out my accidents_id. The only way I found around that is to change Accidents[] to Set.
How can I keep Accidentsas an array and not have Hibernate force this 2nd update after the insert?