I have the following POJOs'
Filter ----> Filter Components
#Entity
public class Filter {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
//Setters and getters are not shown
And I have the following child class
#Entity
public class FilterComponents {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private int component_id;
private int component_type;
#ManyToOne
#JoinColumn(name = "filter_id")
private Filter filter;
//Setters and getters are not shown
I created a repository to query for Filters
public interface FilterRepository extends JpaRepository <Filter, Long> {}
I am calling the findAll() function to get all Filters. The function is working fine; however, it only returns the name and id of each filter.
Is there a way to return the corresponding Filter Components as well? I assume I can write a join query, but I have a feeling that there is a cleaner way to do it!
Thank you
Make Filter to FilterComponents a OneToMany unidirectional mapping. So, you will be managing child FilterComponents inside its parent.
#Entity
public class Filter {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#OneToMany
#JoinColumn(name = "filter_id")
private List<FilterComponents> filterComponenets;
}
#Entity
public class FilterComponents {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private int component_id;
private int component_type;
// Removed mapping
}
What you probably missing is a filterComponents field for a Filter e.g.
public class Filter {
...
#OneToMany(mappedBy="cart")
private List< FilterComponents> filterComponents;
You can define eager or lazy fetching depending on your needs here
Your Filter entity does not have any explicit association with FilterComponent entity. In this case you would need to do another request to select all filter components with the given filter id.
On the other hand you can declare the following field in the Filter entity:
#OneToMany(mappedBy = "filter", fetch = FetchType.EAGER)
private List<FilterComponent> filterComponents;
and always load filter components eagerly.
If eager loading does not fit you you can use custom query with left join fetch:
select distinct f from Filter f left join fetch f.filterComponents c
Related
I'm getting an exception:
org.hibernate.TransientPropertyValueException:
object references an unsaved transient instance
- save the transient instance before flushing :
com.example.jpamapstruct.entity.Member.club ->
com.example.jpamapstruct.entity.Club
while saving the member entity:
#Transactional
public MemberDto save(MemberDto memberDto){
Member entity = memberMapper.toEntity(memberDto);
return memberMapper.toDto(repository.save(entity));
}
How to fix this case in a proper way?
Possible solution:
I can get and set a club object before saving a member but is it only one and the best approach in such scenario?
Member entity = memberMapper.toEntity(memberDto);
clubRepository.getReferencedById(memberDto.getClubId()).ifPresent(entity::setClub);
return memberMapper.toDto(repository.save(entity));
Questions:
Should I put this getReferencedById code explicity? I mean what if we have several child objects (unidirectional ManyToOne), for each we need to get data from DB.
Is there any way to handle this by JPA (Spring Data/JPA) "automatically"?
Maybe it is possible to hit DB only one time with f.e join fetch somehow for all childs (with using custom #Query or querydsl or criteria/specification)?
Next, hoow to handle collections (unidirectional manyToMany)? In my case set of events in member object. Also need to loop thru and get all objects one by one before saving member?
Where should I put such logic in a service or maybe better in a mapstuct mapper?
If so, how to use repositories in such mapper?
#Mapper(componentModel = "spring")
public interface MemberMapper extends EntityMapper<MemberDto, Member> {
#AfterMapping
default void afterMemberMapping(#MappingTarget Member m, MemberDto dto) {
var club = clubRepo.findById(m.getClub().getId())
m.setClub(club)
}
Source code:
#Entity
public class Club extends AbstractEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Long id;
}
public class ClubDto extends AbstractDto {
private Long id;
}
#Entity
public class Member {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", unique = true, nullable = false)
private Long id;
// commented out as don't want to save child object as it should already exist
// #ManyToOne(cascade = CascadeType.ALL)
#ManyToOne
Club club;
#ManyToMany
#JoinTable(name = "member_events",
joinColumns = #JoinColumn(name = "member_id"),
inverseJoinColumns = #JoinColumn(name = "event_id")
)
List<Event> events = new ArrayList<>();
}
public class MemberDto {
private Long id;
private ClubDto club;
}
#MappedSuperclass
public abstract class AbstractEntity {
#Version
private Integer version;
}
public abstract class AbstractDto {
private Integer version;
}
//MemberMapper above
I want to join column without object reference. is that possible?
I want to do foreign key without object reference like that
#Data
#Entity
#Table(name = "HRM_EMPLOYEE_SALARY_INCREMENT")
public class EmployeeSalaryIncrement implements Serializable {
private static final long serialVersionUID = 9132875688068247271L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="ID")
private Integer id;
#Column(name = "REFERENCE_NO")
private String referenceNo;
#ManyToOne
#JoinColumn(name = "AUTHORITY", referencedColumnName = "id")
private Integer authority;
#ManyToOne
#JoinColumn(name = "PART_TWO_REGISTER_ID")
private Integer partTwoRegisterId;
#Column(name = "PART_TWO_ORDER_NO")
private String partTwoOrderNo;
#Column(name = "REMARKS")
private String remarks;
#Column(name = "HRM_TYPE")
private Integer hrmType;
}
If I found solve this problem, it will helpful for me.
Joining is not needed in this case. If you only need the foreign key value, then simply add the column as a #Column like any other:
#Data
#Entity
#Table(name = "HRM_EMPLOYEE_SALARY_INCREMENT")
public class EmployeeSalaryIncrement implements Serializable {
private static final long serialVersionUID = 9132875688068247271L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="ID")
private Integer id;
#Column(name = "AUTHORITY")
private Integer authority;
// other fields
// ...
}
No, I don't think that you can join columns between two entities without adding the reference of one to the related entity. You will have to create one entity class corresponding to each of your relational database table and add the reference of one to the other to establish relation.
However, I understand that you may not need all the attributes from your related table based upon your use case, and only wish to select one column from it. You can do that either by only adding required attributes in your joined table entity class (if you are sure you won't need other attributes for that table anywhere else).
Or you can use custom queries using JPQL in your repository class which selects only the required attributes from the tables that you have joined.
I will show you an example of the second way:
//Say, this is your entity class where you wish to join other table to fetch only one attribute from the joined table-
#Entity
#Table(name = "TABLE1", schema = "SCHEMA1")
public class Table1 {
#Id
#Column(name = "ID")
private String id;
#Column(name = "TABLE2_COLUMN")
private String table2Column;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "TABLE2_COLUMN1")
private Table2 table2; //refrence of the joined table entity object
}
// And this is the joined table entity class
#Entity
#Table(name = "TABLE2", schema = "SCHEMA1")
public class Table2 {
#Id
#Column(name = "ID")
private String id;
#Column(name = "TABLE2_COLUMN1")
private String table2Column1;
#Column(name = "TABLE2_COLUMN2")
private String table2Column2; // The column which we want to select from the joined table
}
In your repository class -
#Repository
public interface Table1Repository extends JpaRepository<Table1, String> {
#Query("SELECT t1 FROM Table1 t1 WHERE t1.id = :id")
public List<Table1> getTable1Rows(#Param("id") String id);
#Query("SELECT t1.table2.table2Column2 FROM Table1 t1 WHERE t1.id = :id")
public String getTable2Column2(#Param("id") String id);
}
Based upon the response from Markus Pscheidt below, I agree when he said there's no need to join the entities if you only need the attribute which is a foreign key. As foreign key is already present as an attribute in your entity (or table) you are working with.
If you need to fetch any other column apart from foreign key, then you may use JPQL to fetch the exact column that you wish to select.
I have created two entities Book and Book_Category with one-to-many relationship. When I issued BookCategoryRepository.findAll(), I expected hibernate to use 'INNER JOIN' query. But it just issued query to take data from Book_Category.
What I am missing? What should I do to make hibernate issue JOIN query?
Book.java
#Entity
public class Book {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#ManyToOne
#JoinColumn(name = "book_category_id")
private BookCategory bookCategory;
}
BookCategory.java
#Entity
#Table(name = "book_category")
public class BookCategory {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#OneToMany(mappedBy = "bookCategory", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Set<Book> books;
}
BookCategoryRepository.java
public interface BookCategoryRepository extends JpaRepository<BookCategory, Integer> {
}
bookCategoryRepository.findAll()
Hibernate uses by default a second query to retriev the child collection. One reason for this is a proper limit query. Otherwise, there would be more rows in the result set, than entities for the 1 side, if at least one has more than 1 child.
There exists an annotation to change this behaviour in hibernate which is ignored by the Spring Data Jpa Repositories. The annotation is #Fetch(FetchMode.JOIN). You might consider How does the FetchMode work in Spring Data JPA if you really need this behaviour.
I have two tables. I want to make between them relationship, but the thing is that the child table connects to an attribute in a parent node, which is not a PK. How can I assign a non-PK field as a FK for a table?
Here are the tables. User Information:
#Entity
#Table(name="user")
public class userinformation implements Serializable {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="USER_ID")
private int uID;
#Column(name="LIB_ID")
private String libID;
//Other attributes
}
Lib Information
#Entity
#Table(name="libinfo")
public class Auth {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="AUTH_ID")
private int authID;
#Column(name="LIB_ID")
private String lib_ID;
//Other attributes
}
They both should be linked through libID (surely unique). Any idea how to implement it correctly?
Given:
class User {
#Column(name = "lib_id")
private String libID;
}
you must map the Auth entity as:
class Auth {
#JoinColumn(name = "lib_id", referencedColumnName = "lib_id")
#ManyToOne
private User user;
}
Basically, referencedColumnName is used to inform the JPA provider that it should use a column other than the primary key column of the referenced entity (which is used by default with #ManyToOne mappings).
I have two pojo classes with one-to-many relationship in hibernate
CustomerAccountEnduserOrderDetails.class
#Entity #Table(name="customer_account_enduser_order_details")
public class CustomerAccountEnduserOrderDetails implements Serializable{
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
#Column(name="id")
private Long id;
#ManyToOne(fetch=FetchType.EAGER)
#JoinColumn(name = "product_id", insertable = false, updatable = false)
private CustomerCmsProduct customerCmsProduct;
}
Second is CustomerCmsProduct.class
#Entity
#Table(name="customer_cms_product")
#JsonIgnoreProperties(ignoreUnknown = true)
public class CustomerCmsProduct {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name="id")
private Long id;
#Column(name="name")
private String name;
#Column(name="offer_price")
private String offerPrice;
#Column(name="original_price")
private String originalPrice;
#Column(name="discount")
private String discount;
}
Here if I fetch the object of CustomerAccountEnduserOrderDetails class,then i will get the CustomerCmsProduct class also , my problem is that here i want the specific column of CustomerCmsProduct table (not all by default i am getting all) like only id and originalPrice.
How i can do like that projection here?
In the service layer or at a webservice layer( if this is a web project) Create two different classes other than #Entity as DTO(Data Transfer Objects) which helps is data transfer from one layer to the other.
public class CustomerAccountEnduserOrderDetailsPojo {
private List<CustomerCmsProductPojo> productPojoList = new ArrayList<> ();
// getter and setter
}
public class CustomerCmsProductPojo {}
Follow the below steps
Retrieve the #Entity class data by executing the query from service layer.
Iterate over all the fields and copy only required fields to pojo layer
Expose the data to other layers using service method.
This way, we can avoid changing the custom hibernate behavior as it is linked with many parameters like cache, one to many queries that are fired per iteration.
And also, do any customization that you want in this layer. Hope this is multi layered project where you have different layers which servers different purpose.