In my spring boot project I have a Document class that has a bi-directional OneToOne relationship to an Invoice class, which share the same ID.
Document
public class Document {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToOne(cascade = CascadeType.ALL)
#PrimaryKeyJoinColumn
private Invoice invoice;
Invoice
public class Invoice {
#Id
#Column(name = "document_id")
private Long documentId;
#OneToOne(mappedBy = "invoice")
#MapsId
#JoinColumn(name = "document_id")
private Document document;
The document entity is created prior to the invoice entity. Later on I create an invoice entity via a MapStruct DTO-Mapping. I then save the entity to "generate" the document_id value.
After saving the invoice entity, I assign the invoice entity to the document entity and save the document entity via the repository. However, the relation to the invoice entity is not persisted in the database.
The invoice entity persists as should be with the corresponding document_id as primary key.
Service code
Invoice newInvoice = invoiceMapper.fromDto(dto);
newInvoice = invoiceRepository.save(newInvoice);
document.setInvoice(newInvoice);
documentRepository.save(document);
InvoiceMapper
#Mapper(componentModel = "spring", nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE, uses = {DocumentService.class})
public interface InvoiceMapper {
#BeanMapping(ignoreByDefault=true)
#Mapping(source = "document", target = "document")
Invoice fromDto(Dto dto);
Previously, I tried mapping the document_id in the MapStruct mapper aswell, but then I received an "attempted to assign id from null one-to-one property" exception on save (even though document and document_id were correctly defined).
When debuggin the code, it correctly shows that the invoice entity was set on the document entity, but unfortunately it is not persisted in the database.
Curiously, I am almost certain that at some point in the coding process it did work as intended. But I can not figure out where the issue is. Help would be much appreciated.
This is not setup correctly as you have not specified anything to set the Invoice's document_id column - you'd have to set this yourself from the documentId long. You must pick one side to have a foreign key to the other - presumably the Invoice has the foreign key to Document and is going to use that as its primary key as well. If that is the case, this needs to be:
public class Invoice {
#Id
#Column(name = "document_id")
private Long documentId;
#OneToOne //this is the owning side of the relationship!
#MapsId
#JoinColumn(name = "document_id")
private Document document;
..
}
public class Document {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToOne(mappedBy = "document")
private Invoice invoice;
..
}
MappedBy indicates that the other side controls setting the foreign key values. Note though that your Invoice will not have a documentId value set, and that you do not need to manually set it. The MapsId annotation tells JPA to pull the value from the Document ID when it is generated and to use that for the document_id column, and will set the documentId Long at the same time.
This then will allow you to create a new Document and Invoice and just call save on the document - once. It isn't enough to just add an invoice to the document - the ID within Invoice is entirely controlled by the Invoice.document reference, so if it isn't set, it will be left null. You must maintain both sides of bidirectional relationships yourself to have the model in synch with what you want in the database. Or at least set the owning side of any bidirectional relationship.
Related
I have been playing around with JPA and came across this scenario and wanted to know how to solve this.
I have 2 tables namely Company and Employee.
So here an employee can work for only 1 company, therefore #OneToOne uni-directional mapping is done in Employee class. And the company details in the Company table would already exist.
So when I try to insert a record into Employee table, I even create a reference to the company, add it to the Employee class and save it using my EmployeeRepository's save method. Since the company_id would already exist in Company table, it should just refer it instead of creating a new company. But this is not happening.
I get an exception saying company object is still in the transient state. I can solve this by adding CascadeType.All but I don't need to insert the company rather I have to just link the company to the employee.
Here are the code snippets.
Employee Class
#Entity
#Table(name = "employee")
#Setter
#Getter
public class Employee
{
#Id
#GeneratedValue
private Long id;
#Column(name = "employee_id")
private Integer employeeId;
#Column(name = "employee_name")
private String employee_name;
#OneToOne
#JoinColumn(name = "company_id")
private Company company;
}
Company class
#Entity
#Table(name = "company")
#Setter
#Getter
public class Company
{
#Id
#GeneratedValue
#Column(name = "company_id")
private Long id;
#Column(name = "company_name")
private String companyName;
}
Company Table
company_id company_name
1 Dell
2 Apple
3 Microsoft
Here is how I am creating the Employee object
Employee emp = new Employee();
emp.setEmployeeId(10);
emp.setEmployeeName("Michael");
Company company = new Company();
company.setId(1);
emp.setCompany(company);
employeeRepository.save(emp);
Please, someone, let me know how to link the company class to an employee class rather than saving one more company.
The best solution for me is to lazy load your company with a proxy. To do it with Spring Data JPA, you need to make your company repository extends JpaRepository. That give you access to the method getReferenceById :
Employee emp = new Employee();
emp.setEmployeeId(10);
emp.setEmployeeName("Michael");
emp.setCompany(companyRepository.getReferenceById(1))
employeeRepository.save(emp);
If there is no company for the given id, an EntityNotFoundException is throw.
With a proxy, you avoid the request to the database in most case because Hibernate use its cache for check the existence of the company. But if my memory serves me correctly, Hibernate gonna make a request to the database at each call to a getter of the proxy, except for getId(). So, in your case it's a good solution, but don't use it all the time.
Assuming the Company may have more than one Employee the relation is a ManyToOne, not a OneToOne.
If you want to reference an existing entity, load it instead of creating a new one:
Employee emp = new Employee();
// ...
emp.setCompany(companyRepository.findById(1));
employeeRepository.save(emp);
I see in most of the coders save data(using spring data) as:
savedEntity = repo.save(savedEntity);
Long id = savedEntity.getId();
I am confused about why most of them assign back the returned value to the saved Entity while the following code also works exact(I have tested myself):
repo.save(savedEntity);
Long id = savedEntity.getId();
Did I miss some benefit of assigning back?
for example, let the entity be:
#Entity
public class SavedEntity {
#Id
private int id;
private String name;
//getter, setters, all arg-constructor, and no-arg constructor
}
Consider the object of SavedEntity is
SavedEntity entity = new SavedEntity(1,"abcd");
now for your first question,
SavedUser entity1 = repo.save(entity);
Long id = entity1.getId();
this entity1 object is the return object getting from the database, which means the above entity is saved in the database succesfully.
for the Second Question,
repo.save(entity);
Long id = entity.getId();//which you got it from SavedEntity entity = new SavedEntity(1,"abcd");
here the value of id is the integer you mentioned in place of id(the raw value).
Most of the time the id (primary key) is generated automatically while storing the entity to the database using strategies like AUTO, Sequence etc. So as to fetch those id's or autogenerated primary key values we assign back the saved entity.
For example:
#Entity
public class Customer {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String firstName;
private String lastName;
}
In this case you'll not pass the id externally but it will create a value for it automatically while storing the data to DB.
I have an application that teaches the user how to play various card games. The data model that gets persisted consists of a TrainingSession with a uni-directional one-to-many relationship with the Hands.
[EDIT] To clarify, a Hand has no existence outside the context of a TrainingSession (i.e they are created/destroyed when the TrainingSession is). Following the principals of Data Driven Design, the TrainingSession is treated as an aggregate root and therefore a single spring-data CrudRepository is used (i.e., no repository is created for Hand)
When I try to save a TrainingSession using a CrudRepository, I get: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (blackjack.hand, CONSTRAINT FKrpuxac6b80xc7rc98vt1euc3n FOREIGN KEY (id) REFERENCES training_session (tsid))
My problem is the 'save(trainingSession)' operation via the CrudRepository instance. What I don't understand is why the error message states that FOREIGN KEY (id) REFERENCES training_session (tsid)). That seems to be the cause of the problem but I cant figure out why this is the case or how to fix it. The relationship is uni-directional and nothing in the Hand class refers to the TrainingSession.
The code, minus all the getters and setters, is:
#Entity
public class TrainingSession {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer tsid;
private String strategy;
#OneToMany(cascade=CascadeType.ALL)
#JoinColumn(name="id")
private List<Hand> hands;
private int userId;
protected TrainingSession() {
}
public TrainingSession(int userId, Strategy strategy, List<Hand> hands) {
this.strategy = strategy.getClass().getSimpleName();
this.hands = hands;
this.userId = userId;
}
while Hand is
#Entity // This tells Hibernate to make a table out of this class
public class Hand {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private int p1;
private String p1s;
private int p2;
private String p2s;
private int d1;
private String d1s;
private int trials;
private int score;
public Hand() {
}
You need to save your TrainingSession and Hand objects first before saving the adding the hand objects to TrainingSession.
TrainingSession ts1 = new TrainingSession();
trainingSessionManager.save(ts1);
Hand hand1 = new Hand();
handManager.save(hand1);
Hand hand2 = new Hand();
handManager.save(hand2);
ts1.gethands().add(hand1);
ts1.gethands().add(hand2)
trainingSessionManager.save(ts1);
If you check your database you will find 3 tables TrainingSession, Hand and TrainingSession_Hand, The TrainingSession_Hand table references to both TrainingSession and Hand both. Therefore you need to save TrainingSession and hand before saving the relationship.
Found the problem. I was assuming that when spring-data set up the DB tables, it was able to figure out and set up the uni-directional 1-to-many relationship. Apparently that isn't the case. When I configure the relationship as bi-directional everything seems to work.
To fix things I:
removed from TrainingSession the #joincolumn annotation for hands
in Hands I added a TrainingSession field with a #ManyToOne annotation:
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "tsid", nullable = false)
#OnDelete(action = OnDeleteAction.CASCADE)
private TrainingSession tsession;
I also added in the Hand class the getter/setter for tsession
I can now do a save of the entire aggregate construct using only a TrainingSessionRepository.
I am using Spring Data JpaRepository to find List of entities matching a particular field. Consider the following code snippet:
Entity:
#Entity
#Table(name = "master")
#Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Master implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
#SequenceGenerator(name = "sequenceGenerator")
#Column(name = "id", nullable = false)
private Long Id;
#NotNull
#Column(name = "user_id", nullable = false)
private String userId;
#OneToOne(fetch = FetchType.EAGER)
#JoinColumn(name="id", referencedColumnName="id", insertable=false, updatable=false)
private Details Details;
Spring Data Custom JpaRepository:
public interface MasterRepository extends JpaRepository<Master,Long> {
List<Master> findMasterByUserId(String userId);
}
When i am using findBookingMasterByUserId repository method to find all records with specific user id, I am getting the List of Master entity but I am not getting the Details entity that has id as foreign key in it.
However, I get all the dependent entities when I use out of the box findAll method of JpaRepository but with custom findMasterByUserId repository method, child entities are not being fetched eagerly.
Any type of help would be highly appreciated. Thanks!
You can use #EntityGraph in your repo to eagerly get associated data:
#EntityGraph(attributePaths = {"details"})
List<Master> findBookingMasterByUserId(String userId);
P.S. Don't forget to change 'Details' field to details;
Your entity name is "Master" not "booking_master".
Change your method to:
List<Master> findByUserId(String userId);
Refer to below spring docs for more information on query creation mechanism for JPA.
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/
Alternatively,
#Query("SELECT m FROM Master m WHERE m.userId = :userId")
List<Master> findByUserId(#Param("userId") String userId);
The query generation from the method name is a query generation strategy where the invoked query is derived from the name of the query method.
We can create query methods that use this strategy by following these rules:
The name of our query method must start with one of the following
prefixes: find…By, read…By, query…By, count…By, and get…By.
If we want to limit the number of returned query results, we can add
the First or the Top keyword before the first By word. If we want to
get more than one result, we have to append the optional numeric
value to the First and the Top keywords. For example, findTopBy,
findTop1By, findFirstBy, and findFirst1By all return the first entity
that matches with the specified search criteria.
If we want to select unique results, we have to add the Distinct
keyword before the first By word. For example, findTitleDistinctBy or
findDistinctTitleBy means that we want to select all unique titles
that are found from the database.
We must add the search criteria of our query method after the first
By word. We can specify the search criteria by combining property
expressions with the supported keywords.
If our query method specifies x search conditions, we must add x
method parameters to it. In other words, the number of method
parameters must be equal than the number of search conditions. Also,
the method parameters must be given in the same order than the search
conditions.
I have two entities :
#Entity
#Table(name="Registration")
public class Registration{
#Id
private UUID uuid;
#OneToMany(cascade = {CascadeType.PERSIST, CascadeType.REMOVE, CascadeType.MERGE}, fetch = FetchType.LAZY)
#JoinColumn(name="registration", nullable = false)
private List<Payment> payment;
}
#Entity
#Table(name="Payment")
public class Payment {
#Id
private UUID uuid;
/*#ManyToOne(targetEntity = Registration.class) <-- MappingException: Repeated column in mapping for entity
private Registration registration;*/
}
This entities create two tables :
TABLE `registration` (
`uuid` binary(16) NOT NULL,
PRIMARY KEY (`uuid`))
TABLE `payment` (
`uuid` binary(16) NOT NULL,
`registration` binary(16) NOT NULL,
PRIMARY KEY (`uuid`),
CONSTRAINT `FK_jgemihcy9uethvoe3l7mx2bih` FOREIGN KEY (`registration`) REFERENCES `registration` (`uuid`))
I'm using Rest Service. I can access to
registration.payment
but not
payment.registration
why ? I need a relation oneToMany bidirectionnal ?
Yes, you need to add the payment.registration #ManyToOne relationship if you use it in your code.
Take into account that JPA allows you to map a SQL database model to an object oriented one. Once you have the mapping between your objects and your database, you always work at the object level. That's why, although you have the relationship in the database, your Payment object doesn't know anything about it unless you map it to an attribute.
Of course it applies when you are using you data model objects or performing JPQL or Criteria queries. If you use native queries you have access to the database model as it is.