I am trying to use hibernate to retrieve data from my database...I have a query that joins two tables (all fields being one to one) using a left join. I need to know how to handle this with hibernate and annotations. I have created two classes that map to tables and I am trying to figure out how to use the joins...Hibernate docs are confusing...
//one class
#Entity
#Table(name = "Class1")
public class Class1{
#Id
#Column(name = "INITIAL")
private String initial;
#Column(name = "NUMBER")
private Integer number;
...
//twoclass
#Entity
#Table(name = "Class2")
public class Class2{
#Column(name = "STATE")
private String state;
#Id
#Column(name = "NUMBER")
private Integer number
...
#Entity
#Table(name = "Class1")
public class Class1 {
#Id
#Column(name = "INITIAL")
private String initial;
#Column(name = "NUMBER")
private Integer number;
}
#Entity
#Table(name = "Class2")
public class Class2 {
#Id
#Column(name = "STATE")
private String state;
#Column(name = "NUMBER")
private Integer number
#OneToOne
#JoinColumn(name = "columnWithClass1id")
private Class1 class1;
}
Related
I have a table that holds events where the data is stored as a JSON object.
What i'am trying to do is have different entities mapped to the same table, because some of these events need to join with other tables to be useful.
What i tried doing:
EntityA is the "default" entity for the table, all events are received in this entity an them stored.
#Entity(name = "entity_a")
#Table(name = "table_a")
public class EntityA {
#Id
private UUID id;
#Column(name = "fielda")
private String fieldA;
#Column(name = "fieldb")
private Integer fieldB;
#Column(name = "json_field")
private Object jsonField;
}
EntityAB is a map of the same table with a new field that is a join with another table.
#Entity(name = "entity_ab")
#Table(name = "table_a")
public class EntityAB {
#Id
private UUID id;
#Column(name = "fielda")
private String fieldA;
#Column(name = "fieldb")
private Integer fieldB;
#Column(name = "json_field")
private Object jsonField;
#ManyToOne
#ManyToOne
#JoinColumnsOrFormulas(value = {
#JoinColumnOrFormula(formula = #JoinFormula(value = "JSON_VALUE(jsonField, '$.field_id_a')", referencedColumnName = "field_id_a")),
#JoinColumnOrFormula(formula = #JoinFormula(value = "JSON_VALUE(jsonField, '$.field_id_b')", referencedColumnName = "field_id_b")),
#JoinColumnOrFormula(formula = #JoinFormula(value = "JSON_VALUE(jsonField, '$.fieldc')", referencedColumnName = "fieldc")),
})
private EntityB entityB;
}
EntityB is used in the EntityAB.
public class EntityB implements Serializable {
#EmbeddedId
private EntityBId id;
#Column(name = "fieldc")
private String fieldC;
}
#Embeddable
public class EntityBId implements Serializable {
#Column(name = "field_id_a")
private String fieldIdA;
#Column(name = "field_id_b")
private Integer fieldIdB;
#Column(name = "field_id_c")
private Integer fieldIdC;
}
When starting the application, it gives me this error:
referencedColumnNames(field_id_a, field_id_b, fieldc) of EntityAB.entityB referencing EntityB not mapped to a single property
If i dont use the fields "field_id_a" and "field_id_b" (EmbeddedId) in the join, it works, but it's not the right join. From what i have searched it looks like i can't have a parcial PK join when using "EmbeddedId", is that correct?
#Entity
#Table(name = "person")
public class Consignment implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "person_id")
private String personId;
#Column(name = "person_name")
private String personName;
#OneToMany(fetch = FetchType.EAGER, mappedBy = "person")
#Column(name = "cars_owned")
private Set<Cars> casrsowned = new HashSet<>();
}
#Entity
#Table(name = "cars")
public class Cars implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "cars_id")
private String carsId;
#ManyToOne
#JoinColumn(name = "person")
private Person person;
#OneToOne
private CarsDetail carsDetail;
}
#Entity
#Table(name = "carsDetail")
public class CarsDetail implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name = "brand")
private String brand;
#Column(name = "color")
private String color;
#Column(name = "model")
private String model;
}
class CarModelDTO {
String personName;
List<String> models;
}
In the above relation, want to return CarModelDTO
JPA query where,
#Query("Select CarModelDTO(p.personName, p.casrsowned.carsDetail.model) from Person as p where p`enter code here`.id = :id"))
public CarModelDTO getCarmodelOwnedByAperson(#Param("id") Long id);
I tried multiple ways but it gives
org.hibernate.QueryException: illegal attempt to dereference collection
As I have already described Retrieve List from repository interface to DTO list you should go through the following step :
first create a constructor using the fields you want to be returned from the query output
in you query you should create new instance of your dto and pass the field from db to new instalnce :
so you need these changes:
1. In the constructor:
You should not use a list as List<String> models; as you should consider that your dto as a result row of DB. so you need to have a simple String model;
public CarModelDTO (String name,String model){
this.name=name;
this.model=model;
}
2. In the #Query:
you should use multi inner join appropriately
you should also append your package name to CarModelDTO in the query (here i used com.example you should change it)
#Query("Select com.example.CarModelDTO(p.personName, d.model ) from Person as p inner join p.carsowned c inner join c.carDetail d where p`enter code here`.id = :id"))
public CarModelDTO getCarmodelOwnedByAperson(#Param("id") Long id)
I am trying to map a bidirectional One-to-Many relationship in Hibernate. In the build logs I receive the error "repeated column in mapping for entity."
What is generating the error?
The entity source code is below. One has a compound primary key. I am using Lombok to generate getters and setters.
The relationship: Award (One) --> AwardReceived (Many)
Award Entity
#Entity
#Table(name = "awards")
#JsonInclude(JsonInclude.Include.NON_NULL)
#Data
public class Award implements Serializable {
#Id
#Column(name = "award_id")
private Long awardId;
#OneToMany(cascade=CascadeType.ALL, mappedBy = "award")
private Set<AwardReceived> awardsReceived;
#Column(name = "award_type")
private String awardType;
#Column(name = "award")
private String award;
#Column(name = "description")
private String description;
}
AwardReceived Entity
#Entity
#Table(name = "awards_received")
#JsonInclude(JsonInclude.Include.NON_NULL)
#Data
public class AwardReceived implements Serializable{
#EmbeddedId
#JsonUnwrapped
private AwardReceivedPk awardReceivedPk;
#ManyToOne(cascade=CascadeType.ALL)
#JoinColumn(name = "award_id")
private Award award;
#Column(name = "award_name")
private String awardName;
#Column(name = "citation")
private String citation;
}
AwardReceivedPk
#Embeddable
#JsonInclude(JsonInclude.Include.NON_NULL)
#Data
public class AwardReceivedPk implements Serializable{
#JsonIgnore
#Column(name = "client_no")
private String clientNo;
#Column(name = "award_id")
private Long awardId;
#Column(name = "year")
private Long year;
}
Please try
#ManyToOne(cascade=CascadeType.ALL)
private Award award;
instead of
#ManyToOne(cascade=CascadeType.ALL)
#JoinColumn(name = "award_id")
private Award award;
I am trying some hibernate.The following is the pojo I am using,
#Entity
#Table(name = "person")
public class Person {
#Id
#GeneratedValue
#Column(name = "person_id")
private long person_id;
#Column(name = "name")
private String name;
#Column(name = "Address")
private String Address;
#OneToMany(fetch = FetchType.EAGER, mappedBy = "person" )
private Set<Phone> phone;
//Getters ande Setters
}
#Entity
#Table(name = "phone")
public class Phone{
#Id
#GeneratedValue
#Column(name = "phone_id")
private long phone_id;
#Column(name = "name")
private String name;
#ManyToOne(cascade = CascadeType.MERGE,fetch = FetchType.EAGER)
#JoinColumn(name = "person_id")
private Person person ;
//Getters ande Setters
}
What I want is when I fetch a record from person and need corresponding all phone details. (Like Select * from person) I have around 1360 data in person and nearly double in phone. But for some reason error is thrown. I am not able to see full error stack . Below is the error I am getting.
at
com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:117)
~[jackson-databind-2.4.6.jar:2.4.6] at
com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:23)
~[jackson-databind-2.4.6.jar:2.4.6] at
.....
I was not able to post all error that I got
Using JsonManagedReference and JsonBackReference annotations may solve your problem.
While jackson trying to convert objects to json, visits objects and
their attributes. So if objects have bi-directional relations, for
jackson we need to think about cyclic dependencies. Jackson starts
serialize person and see the phone list and take a phone from list and
start serialize phone and sees person in phone and take person from
phone and start serilize it bla bla bla so this is an endless loop. If
jackson sees these annotations, stops and breaks the loop.
Give it a try as below code;
#Entity
#Table(name = "person")
public class Person {
#Id
#GeneratedValue
#Column(name = "person_id")
private long person_id;
#Column(name = "name")
private String name;
#Column(name = "Address")
private String Address;
#JsonManagedReference
#OneToMany(fetch = FetchType.EAGER, mappedBy = "person" )
private Set<Phone> phone;
// Getters and Setters
}
#Entity
#Table(name = "phone")
public class Phone{
#Id
#GeneratedValue
#Column(name = "phone_id")
private long phone_id;
#Column(name = "name")
private String name;
#ManyToOne(cascade = CascadeType.MERGE,fetch = FetchType.EAGER)
#JoinColumn(name = "person_id")
#JsonBackReference
private Person person;
// Getters and Setters
}
You can alternatively use #JsonIdentityInfo on classes
#Entity
#JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="#id")
#Table(name = "phone")
public class Phone {
}
#Entity
#JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="#id")
#Table(name = "person")
public class Person {
}
I was also getting the same error.
Using #JsonBackReference and #JsonManagedReference was still giving me error so I used #JsonIdentityInfo and it worked like a charm.
Below are my classes :-
BookModel :
#Data
#Entity
#Table(name = "book")
#JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="bookId")
public class BookModel implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "book_id")
private int bookId;
#Column(name="book_name")
private String bookName;
#Column(name="book_author")
private String bookAuthor;
#Column(name="book_publish_date")
private Date bookPublishDate;
#Column(name="book_price")
private double bookPrice;
#OneToMany(mappedBy = "book_model")
List<BookImagesModel> bookImagesModels;
//getters and setters
//default constructor
}
BookImagesModel :
#Data
#Entity
#Table(name = "book_images")
#JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="imageId")
public class BookImagesModel implements Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "image_id")
private long imageId;
#ManyToOne
#JoinColumn(name = "book_id")
private BookModel book_model;
#Column(name = "image_path")
private String imagePath;
//getters and setters
//default constructor
}
I used Mysql8 database with spring boot.
I am new to JPA and doing a small sample to learn about it.
But I got one problem below, please help me out, and please explain why:
I have class Customer.java, which is mapped to table customer in db:
#Entity
public class Customer implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name = "id_customer")
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;
// accountNumber field maps with accountNumber column in Account table
#Column(name = "loginId", unique = true)
private String loginId;
#Column(name = "password")
private String password;
#Column(name = "firstName")
private String firstName;
#Column(name = "lastName")
private String lastName;
#Column(name = "address")
private String address;
#Column(name = "email")
private String email;
#Column(name = "phone")
private String phone;
#OneToMany(mappedBy="customer")
private List<Account> accountList;
#OneToMany(mappedBy="customer")
private List<Card> cardList;
// getters and setters goes here
}
The above class has two lists, accountList and cardList, their generic Class (Card and Account) extends BaseInfo using Single table Inheritance.
Here is my BaseInfo.java:
#Entity
#Table(name = "account")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn(name = "discriminator", discriminatorType = DiscriminatorType.STRING)
public class BaseInfo implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name = "number")
private String number;
#Column(name = "availableNumber")
private Long availableNumber;
//getter and setter here
}
Class Card.java:
#Entity
#Table(name = "account")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorValue(value = "C")
public class Card extends BaseInfo implements Serializable {
private static final long serialVersionUID = 1L;
#Column(name = "cardType")
private String cardType;
#ManyToOne
#JoinColumn(name = "id_customer")
private Customer customer;
//getter and setter
}
And class Account.java:
#Entity
#Table(name = "account")
#Inheritance(strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorValue(value = "A")
public class Account extends BaseInfo implements Serializable {
private static final long serialVersionUID = 1L;
#Column(name = "accountName")
private String accountName;
#Column(name = "accountType")
private String accountType;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "dt_created")
private Date createdDate;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "dt_lst_updt")
private Date lastUpdatedDate;
#ManyToOne
#JoinColumn(name = "id_customer")
private Customer customer;
//getter, setter
}
Then, I do a query that query customer from database with loginid and password, like this:
entityTransaction.begin();
TypedQuery<Customer> query = entityManager.createQuery(
"SELECT c FROM " + Customer.class.getName()
+ " c Where c.loginId= :loginId", Customer.class);
query.setParameter("loginId", loginId);
res = query.getSingleResult();
entityTransaction.commit();
The code run with no error, but the result is somethings strange to me: When I debug (or print out the result to jsp), accountList or cardList contains all Account of that customer, just like they don't care about the 'discriminator' column.
I have 2 questions:
How can I archive the goal that listCard contains only Card (discrimination = c) and listAccount contains only Account (discriminator = a) ?
Is there an alternative way to query listCard or listAccount without query the customer first (like I use) ??
Thank in advance! :D
I'm not sure if it's a JPA restriction or a Hibernate-specific restriction, but you may not use the same column to map two different associations.
You should use something like car_customer_id to map the association between customer and cards, and account_customer_id to map the association between customer and accounts.