Suppose I have entities (getters/setters and various details omitted for brevity):
#Entity
class Customer{
...
#OneToMany(cascade = CascadeType.ALL, mappedBy = "customer")
Collection<Coupon> coupons;
}
#Entity
class Coupon{
...
#Temporal(value = TemporalType.TIMESTAMP)
private Date usedOn;
#ManyToOne(fetch = FetchType.LAZY)
#NotNull
Customer customer;
}
I wish retrieve all Coupons for a given Customer having null usedOn.
I,'ve unsuccessfully defined a method in the CouponRepository as described in docs
#Repository
public interface CouponRepository extends CrudRepository<Coupon, Long> {
Collection<Coupon> findByCustomerAndUsedOnIsNull(Customer);
}
but this leads on a compiler error Syntax error, insert "... VariableDeclaratorId" to complete FormalParameterList.
My fault, the correct definition is
#Repository
public interface CouponRepository extends CrudRepository<Coupon, Long> {
Collection<Coupon> findByCustomerAndUsedOnIsNull(Customer customer);
}
I simply missed the parameter name :-(
You can use IsNull to check null columns in JPA query.
For example for any columnA you can write query like query like
findByColumnAIsNull
In this case you can write queries like
#Repository
public interface CouponRepository extends CrudRepository<Coupon, Long> {
Collection<Coupon> findByCustomerAndUsedOnIsNull(Customer customer);
List<Coupon> findByUsedOnIsNull();
}
Also you can check how this queries will be
Refer this Spring Data JPA Query creation this will help you lot to understand and create different type of JPA query variation.
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.query-creation
Try changing your method to this (assuming Customer.id is a long):
Collection<Coupon> findByCustomer_IdAndUsedOnIsNull(Long customerId);
then use like this:
repo.findByCustomer_IdAndUsedOnIsNull(customer.getId());
Related
#Entity
class Person{
private int id;
#OneToMany(mappedBy=owner)
private List<Pet> pets;
}
#Entity
class Pet{
private name;
private ZonedDateTime birthDate;
#ManyToOne
#JoinColumn(name="owner_id")
private Person owner;
}
I want to find all the persons and order them by their oldest pet birthday
The only way I can solve this is through #Formula , something like
#Entity
class Person{
private int id;
private List<Pet> pets;
#Formula("(SELECT p.birth_date FROM pet p WHERE p.owner_id = id order by p.birth_date ASC LIMIT 1)")
private ZonedDateTime oldestPetBirthday;
}
then
public List<Person> findPersonByOrderByOldestPetBirthdayAsc
But I don't want to touch raw sql, I am looking for something like
public List<Person> findPersonByOrderByPetsTop1OrderByBirthDateAsc
OR by using pageable something like:
PageRequest.of(page,pageSize,Sort.by(ASC, "pets.sort(BirthDateComparator).get(0)"))
is that possible?
Try to use #OrderBy annotation from #javax.persistence.OrderBy package on your one to many collection object.
#OrderBy("birthDate")
private List<Pet> pets;
Your solution with the formula is ok but suffers from some issues. Anyway, since you don't want to write SQL, you will have to use something like 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(Person.class)
public interface PersonDto {
#IdMapping
Long getId();
#Limit(limit = "1", order = "birthDate desc)
#Mapping("pets")
OldestPetDto getOldestPet();
#EntityView(Pet.class)
interface OldestPetDto {
#IdMapping
Long getId();
ZonedDateTime getBirthDate();
}
}
Querying is a matter of applying the entity view to a query, the simplest being just a query by id.
PersonDto a = entityViewManager.find(entityManager, PersonDto.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<PersonDto> findAll(Pageable pageable);
The best part is, it will only fetch the state that is actually necessary!
Also, you can add a Sort for oldestPet.birthDate and it will work just like you would like it to!
Is it possible to use JPA derived methods and query by example at the same time?
Let's imagine i have two entities like this:
#Entity
#Data
public class Person {
#Id
#GeneratedValue
Long id
String name;
String surname;
#OneToMany
List<Dog> dogs;
}
#Entity
#Data
public class Dog{
#Id
#GeneratedValue
Long id
String name;
}
I'd like to be able to do something like this (just an example):
Person p = new Person ();
p.setName("Mario");
personRepository.findDistinctByDogsIsNotNull(Example.of(p));
The Example.of(p) only works if i do findAll, but it doesn't work if i define inside the repository a method like this
private interface PersonRepository extends JpaRepository<Person, Long>{
List<Person> findDistinctByDogsIsNotNull(Example<Person> example)
}
The error it gives me is something like this:
Failed to create query for method public abstract java.util.List dev.cele.test.repository.PersonRepository.findDistinctByDogIsNotNull(org.springframework.data.domain.Example)! At least 1 parameter(s) provided but only 0 parameter(s) present in query.
So my question is: is it possible to do a query by example in a JPA derived query method?
And if it's not possible how can i create some sort of parametrizable query that also has a predetermined condition?
I was trying to use #MappedSuperclass to share the same table between two entities following this article here (How to map multiple JPA entities to one database table with Hibernate),
So I have these 3 classes:
#MappedSuperclass
abstract class UserDao {
#Id
#Column(name = "username", nullable = false, unique = true)
var username: String? = null
#OneToMany(fetch = FetchType.EAGER)
var groups: Set<GroupDao>? = null
}
then:
#Entity(name = "basic_user_auth")
#Table(name = "users")
class BasicUserDao : UserDao() {
}
and:
#Entity(name = "full_auth_user")
#Table(name = "users")
class FullUserDao : UserDao() {
#OneToOne
#PrimaryKeyJoinColumn
var profileJpa: ProfileDao? = null
}
what I was trying is to save some queries overhead of loading the user profile when its not needed, but now when i try to run the app i get the following error:
could not execute statement; SQL [n/a]; constraint [full_auth_user_username" of relation "users_groups];
not sure why Hibernate creates this relation since they both share the same table.
I would recommend you don't share types on the entity level. Sharing a one-to-many association will probably not work as you expect with respect to flushing/synchronization when multiple such entities are involved. IMO you should try out a DTO approach instead.
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(User.class)
public interface BasicUserDao {
#IdMapping
String getUsername();
Set<GroupDao> getRoles();
#EntityView(Group.class)
interface GroupDao {
#IdMapping
Long getId();
String getName();
}
}
#EntityView(User.class)
public interface FullUserDao extends BasicUserDao {
#Mapping("profileJpa")
ProfileDao getProfile();
#EntityView(Profile.class)
interface ProfileDao {
#IdMapping
Long getId();
String getName();
}
}
Querying is a matter of applying the entity view to a query, the simplest being just a query by id.
BasicUserDao a = entityViewManager.find(entityManager, BasicUserDao.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
#Repository
interface UserRepository {
List<BasicUserDao> findAll();
}
The best thing about it is, that it will only fetch the data that is actually needed.
Am new to Spring Boot & JPA...
Let's say I have two entities mapped to two tables which are joined in a database.
Student-1------<-Course
Also, lets presume that the database is already created and populated.
This depicts that one student has many courses...
My Student Entity:
#Entity
public class Student {
#OneToMany(mappedBy="student")
private List<Courses> courses;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "Student_Id")
private long studentId;
#Column(name = "Student_Name")
private String studentName;
protected Student() { }
// Getters & Setters
}
My Course Entity:
#Entity
public class Course {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "Course_Id")
private long courseId;
#Id
#Column(name = "Student_Id")
private long studentId;
#ManyToOne
#PrimaryKeyJoinColumn(name="Student_Id", referencedColumnName="Student_Id")
private Student student;
#Column(name = "Course_Name")
private String courseName;
// Getters & Setters
}
In Spring Boot's Tutorial Guides, it illustrates how to extend a CrudRepository interface, but
it doesn't specify how to setup a Spring based DAO which contains custom finder methods which use HQL and EntityManager inside it.
Is the following DAO and DaoImpl correct?
public interface CourseDao {
List<Course> findCoursesByStudentName(String studentName);
}
#Repository
public class CourseDaoImpl implements CourseDao {
#PersistenceContext
EntityManager em;
public List<Course> findCoursesByStudentName(String studentName) {
String sql = "select c.courseName" +
"from Course c, Student s " +
"where c.course_id = s.student_id " +
"and s.studentName = :studentName ";
Query query = em.createQuery(sql);
query.setParameter("studentName", studentName);
return query.getResultList();
}
}
And then in the client code, for example, in the main class:
public class Application {
#Autowired
CustomerDao dao;
public static void main (String args []) {
List<Course> courses = dao.findCoursesByStudentName("John");
}
}
Is this the standard way to use HQL inside Spring DAOs ? I've seend examples of the #Transactional annotation being prepended to the DAO class's impl (e.g. CustomerDAOImpl) ?
Please let me know if this is the write way to structure my Spring Boot app or am I supposed to extend / add to the CrudRepository only?
If someone could correct my example and point me to a URL which talks about HQL using Entities that are joined, I would be very grateful.
The Spring Boot guides didn't depict joins or DAOs - I just need to learn how to properly create finder methods which emulate select statement which return lists or data structures.
Thanks for taking the time to read this...
If I understood your question correct you do have two questions:
How to create a DAO and DAOImpl?
Where to put your Transaction annotations?
In regards to the first question I want to point out that this is a question in regards to spring-data-jpa using Hibernate as a JPA provider, not spring-boot.
Using Spring Data I usually skip completely to create a DAO but directly use a Custom Repository extending a standard one like CrudRepository. So in your case you don't even have to write more code than:
#Repository
public interface StudentRepository extends CrudRepository<Student, Long> {
List<Student> findByStudentName(String studentName);
}
Which will be sufficient and Spring Data will take care of filling it with the correct implementation if you use
#Autowired
StudentRepository studentRepo;
in your service class. This is where I also usually annotate my methods with #Transactional to make sure that everything is working as expected.
In regards to your question about HQL please look into the spring data jpa documentation, which points out that for most of the cases it should be sufficient to stick to proper named methods in the interface or go for named queries (section 3.3.3) or use the #Query annotation (section 3.3.4) to manually define the query, e.g. should work (didn't tried):
#Repository
public interface #CourseRepository extends CrudRepository<Course, Long> {
#Query("select c.courseName from Course c, Student s where c.course_id = s.student_id and s.studentName = :studentName")
public List<Course> findCoursesByStudentName(String studentName);
}
If you annotate your CourseDaoImpl with #Transactional (Assuming your have defined JpaTransactionManager correctly) You can just retrieve the Student with the matching name and call the getCourses() method to lazy load the Courses attached to that student. Since findCoursesByStudentName will run within a Transaction it will load the courses just fine.
#Repository
#Transactional(readOnly=true)
public class CourseDaoImpl implements CourseDao {
#PersistenceContext
EntityManager em;
public List<Course> findCoursesByStudentName(String studentName) {
String sql = "select s " +
"from Student s " +
"where s.studentName = :studentName ";
Query query = em.createQuery(sql);
query.setParameter("studentName", studentName);
User user = query.getSingleResult();
if(user != null) {
return user.getCourses();
}
return new ArrayList<Course>();
}
}
I am working with Hibernate 4+ Spring MVC + Spring Data with JPA annotations:
#Entity
public class ClassOne implements Serializable{
......
#OneToMany(mappedBy = "mapper", fetch=FetchType.LAZY)
private Set<ClassTwo> element = new HashSet<ClassTwo>(0);
//more fields
//getters and setters
//equals and hashcode
}
#Entity
public class ClassTwo implements Serializable{
......
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "CEN_CEN_CODIGO", nullable = false)
private ClassOne classOne;
//more fields
//getters and setters
//equals and hashcode
}
public interface ClassOneRepository extends CrudRepository<ClassOne, Long> {
#Override
#Query("select c from ClassOne c")
public List<ClassOne> findAll();
}
#Service
public class ClassOneService {
#Autowired
private ClassOneRepository classOneRepository;
#Transactional(readOnly=true)
public List<ClassOne> findAll() {
return classOneRepository.findAll();
}
}
And finally I call thie service from my #Controller
#Autowired
ClassOneService classOneService;
I expect results ONLY from ClassOne but retrieving the JOIN values with ClassTwo and all the database tree associate. Is it possible to get only values for ONE table using this schema? Is it a cache problem or Fetching not LAZY?
EDIT: I added the relatioship between two classes
Thank you
You must have the following anotation above your Set<ClassTwo> or its getter:
#OneToMany(fetch = FetchType.LAZY, ...)
See http://docs.oracle.com/javaee/7/api/javax/persistence/OneToMany.html#fetch()
It seems to be that simple "SELECT *" JPA query returns all eagerly fetched fields for the entity.
Please refer to: JPA - Force Lazy loading for only a given query
and http://forcedotcom.github.io/java-sdk/jpa-queries.
So my solution would be to use SessionFactory to get current session and then use "classic" method
return getCurrentSession().createCriteria(persistentClass).list();
Another possible way is to create let's say a POJO object without Set which uses the same table as ClassOne.
I've just added #Lazy for each #ManyToOne and #OneToMany relationship. It seems that Spring Data needs Spring annotations but I supposed that just was necessary to add fetch = FetchType.LAZY. No more Eager behaviours ;).
Thanks for your responses