I've been scratching my head for a while and thought I'd get some help :)
I'm working with a legacy database which I cannot change. I have the following domain:
#Entity
public class Institution {
#Id
private Long id;
#OneToMany(mappedBy="institution", fetch=FetchType.EAGER)
private List<Subscription> subscriptions = new ArrayList<Subscription>();
}
#Entity
public class Subscription {
#Id
private Long id;
#ManyToOne
#JoinColumn(name="sub_id", referencedColumnName="ins_sub_id", insertable=false, updatable=false)
private Institution institution;
}
For the sake of brevity I have excluded showing the getters/setters. There is no join table.
So;
1) Is the mapping correct? I want a bidirectional association and I want the Institution to be the owner of the relationship.
2) If I load a Institution, create a new Subscription() and add the subscription to the subscriptions collection...
#RequestMapping(value="/add/{institutionId}", method=RequestMethod.POST)
public String submitSubscriptionForm(#ModelAttribute SubscriptionForm form) {
Institution institution = institutionService.getById(form.getInstitutionId());
Subscription subscription = new Subscription();
//...set properties on subscripton from data in the form
subscription.setInstitution(institution);
institution.getSubscriptions().add(subscription);
institutionService.saveOrUpdateInstitution(institution);
}
...when I save the Institution...
institutionService.saveOrUpdateInstitution(institution); just delegates to a DAO which extends HibernateDaoSupport.
...I get the following error:
org.springframework.orm.hibernate3.HibernateSystemException: Illegal attempt to associate a collection with two open sessions; nested exception is org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:679)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)
at org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)
at org.springframework.orm.hibernate3.HibernateTemplate.saveOrUpdate(HibernateTemplate.java:737)
at com.f1000.dao.hibernate.InstitutionDaoImpl.saveOrUpdate(InstitutionDaoImpl.java:161)
I'm using the Spring and am making use of the OpenSessionInViewFilter and I can't figure out why a second session is created?
There is an issue in your association,
#ManyToOne
#JoinColumn(name="sub_id", referencedColumnName="ins_sub_id")
private Institution institution;
The is a insertable=false, updatable=false set on your institution inside the Subscription. Either you need to remove it or create a new property as below an set that, to the new Subscriptions.
private Long institutionId;
and replace subscription.setInstitution(institution); this by,
subscription.setInstitutionId(institution.getId());
Read here on more about the insertable=false, updatable=false mappings.
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 have a simple project that has a User model, Sports team model and a Many To Many table where a user can "like" the sports team.
User
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "likes",
joinColumns = #JoinColumn(name = "user_id"),
inverseJoinColumns = #JoinColumn(name = "team_id")
)
private List<Team> teamsLiked;
Team
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#NotBlank
#Size(min=2, max=30)
private String teamName;
#NotBlank
private String city;
private String sport;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "likes",
joinColumns = #JoinColumn(name = "team_id"),
inverseJoinColumns = #JoinColumn(name = "user_id")
)
private List<User> likers;
My problem is, when I'm using Spring MVC forms for a user to edit a team, upon submission it completely wipes out existing likes on the Team object under likers. On the edit page, I am using #ModelAttribute and pre populating the existing team object, and have tried to put the likers as a hidden attribute so the data will persist, but that throws an error. I've tried on the #PostMapping backend, to set the origin list of likers before re-saving the DB and that's not working either. Besides using Normal HTML forms to update an object, is there a way I can have the list of users who liked a team persist after updating? Thanks in advance.
What you need here is a DTO and map that onto an existing entity. I think this is a perfect use case for Blaze-Persistence Entity Views.
I created the library to allow easy mapping between JPA models and custom interface or abstract class defined models, something like Spring Data Projections on steroids. The idea is that you define your target structure(domain model) the way you like and map attributes(getters) via JPQL expressions to the entity model.
A DTO model for your use case could look like the following with Blaze-Persistence Entity-Views:
#EntityView(Team.class)
#UpdatableEntityView
public interface TeamDto {
#IdMapping
Long getId();
String getTeamName();
void setTeamName(String teamName);
String getCity();
void setCity(String city);
String getSport();
void setSport(String sport);
}
Querying is a matter of applying the entity view to a query, the simplest being just a query by id.
TeamDto a = entityViewManager.find(entityManager, TeamDto.class, id);
The Spring Data integration allows you to use it almost like Spring Data Projections: https://persistence.blazebit.com/documentation/entity-view/manual/en_US/index.html#spring-data-features
Page<TeamDto> findAll(Pageable pageable);
The best part is, it will only fetch the state that is actually necessary!
And in your case of saving data, you can use the Spring WebMvc integration
that would look something like the following:
#Transactional
#PostMapping("/teams")
void save(#RequestBody TeamDto dto){
repository.save(dto);
}
My User class looks like this :
#Data
#Entity
public class User {
#Id
Long userID;
#ManyToMany(mappedBy = "admins")
private List<ClassRoom> classRooms = new ArrayList<>();
}
And my ClassRoom class like this :
#Data
#Entity
public class ClassRoom {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
Long classRoomID;
#ManyToMany
#JoinTable(name ="classroom_user",
joinColumns = #JoinColumn(name = "classroom_id"),
inverseJoinColumns = #JoinColumn(name = "user_id"))
private List<User> admins = new ArrayList<>();
}
And in my UserController class, I have :
#PostMapping("user/{id}/c")
User addClassRoom(#PathVariable Long id,#RequestBody ClassRoom newClassRoom)
{
logger.debug(repository.findById(id));
return repository.findById(id)
.map(user -> {
user.getClassRooms().add(newClassRoom);
user.setClassRooms(user.getClassRooms());
return repository.save(user);
})
.orElseGet(() -> {
return null;
});
}
And I POST and empty JSON ({}) and I see no change in my users. The Classroom or an empty Classroom doesn't get added in the User.
What is the problem here? How can I resolve this ?
user.getClassRooms().add(newClassRoom); is suffice, user.setClassRooms(user.getClassRooms()); not required.
You will have to perform cascade save operation.List all cascade types explicitly and don't use mappedBy, instead use joincolumns annotation.
Can you paste the logs, please? Is Hibernate doing any insert into your table? Has the database schema been created in the DB correctly? One thing I recommend you to do is to add a custom table name on the top of your User class, using annotations like so: #Table(name = "users"). In most SQL dialects user is a reserved keyword, hence it is recommended to always annotate User class a bit differently, so that Hibernate won't have any problems to create a table for that entity.
IMO you must find classRoom by its id from repository, if it's new, you must create a new entity and save it first. Then assign it to user and save it.
The object you receive from the post method was not created by the entity manager.
After using user.getClassRooms().add(newClassRoom);
We must use userRepository.save(user);
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 have to JPA Entities defined with a bidirectional relationship many to one, hereby:
#Entity
public class Department implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#SequenceGenerator(name="DEPARTAMENTO_ID_GENERATOR",sequenceName="DEPARTAMENTO_SEQ")
#GeneratedValue(strategy=GenerationType.SEQUENCE,generator="DEPARTAMENTO_ID_GENERATOR")
#Column(name="DEP_ID")
private long id;
#Column(name="DEP_DESC")
private String desc;
//bi-directional many-to-one association to Academico
#OneToMany(mappedBy="department")
private Set<Proffesor> proffesors;
//getters and setters
}
#Entity
#Table(name="ACADEMICOS")
public class Proffesor implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#SequenceGenerator(name="ACADEMICOS_ID_GENERATOR", sequenceName="ACADEMICOS_SEQ")
#GeneratedValue(strategy=GenerationType.SEQUENCE,generator="ACADEMICOS_ID_GENERATOR")
#Column(name="ACD_ID")
private long id;
#ManyToOne(cascade={CascadeType.PERSIST,CascadeType.MERGE})
#JoinColumn(name="ACD_DEPADSCRITO_DEP")
private Department department;
// getters and setters.
}
After in a transactional Spring service I have the next code to manipulate the entities in this way.
#Transactional (propagation=Propagation.REQUIRED)
public void createDepartmentWithExistentProffesor(String desc,Long idAvaiableProf) {
// new department
Department dep = new Department();
dep.setDesc(desc);
HashSet<Proffesor> proffesors = new HashSet<Proffesor>();
dep.setProffesors(proffesors);
// I obtain the correct attached Proffesor entity
Proffesor proffesor=DAOQueryBasic.getProffesorById(idAvaiableProf);
// I asign the relationship beetwen proffesor and department in both directions
dep.addProffesors(proffesor);
// Persists department
DAODataBasic.insertDepartment(dep);
// The id value is not correct then Exception ORA-0221
System.out.println("SERVICIO: Departamento creado con id: " + dep.getId());
}
As I said in the comments the id of the new Department persisted is not a real database id inside the transaction, then it is produced an exception
Exception in thread "main" org.springframework.orm.jpa.JpaSystemException: org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
........
Caused by: java.sql.BatchUpdateException: ORA-02291: integrity restiction (HIBERNATE_PRB.FK_ACD2DEP) violated - primary key don't found
I've tried in a test, persist the new departmen entity with no relationship with Proffesor and I've seen that the id of the new department persisted entity has not a valid value inside the transaction but out of the transaction already the id has a correct value.
But I need the correct value inside the transaction.
Can anybody help me?
Thank you in advance.
try this
#OneToMany(mappedBy="department",cascade = CascadeType.PERSIST)
private Set<Proffesor> proffesors;