#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!
Related
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.
My Repository Method Query cannot parse a property name that comes after the OrderBy, but it can if it follows the findBy or findAllBy. The attribute in my entity that is giving me issues is zIndex
Entity Class
#Entity
public class DisplayLayer
{
#Id
#Column(name="DISPLAY_LAYER_ID")
private Long id;
#ManyToOne(cascade = CascadeType.ALL)
#JoinColumn(name="DISPLAY_CONTAINER_ID")
private DisplayContainer displayContainer;
#Column(name="NAME")
private String name;
#Column(name="Z_INDEX")
private Long zIndex;
#Column(name="DESCRIPTION")
private String description;
// Getters & Setters
}
Repository Class
public interface DisplayLayerRepository extends BaseRepository<DisplayLayer, Long>
{
// This one method query works just fine
public List<DisplayLayer> findByZIndex(Long pZIndex);
// These two throw the same error:
// Unable to locate Attribute with the the given name [ZIndex]
//
// public List<DisplayLayer> findAllByOrderByZIndexAsc();
// public List<DisplayLayer> findByDisplayContainerIdOrderByZIndexAsc(Long pDisplayLayerId);
}
So in my first method query, when OrderBy is not used, it correctly parses it as [zIndex], but when it follows the OrderBy for some reason it capitalizes the z: [ZIndex].
Is this a known issue, or am I doing something wrong?
EDIT
What makes me think there might be a bug with the parser is that if I update zIndex to IndexZ in my entity and then change my query methods from OrderByZIndex to OrderByIndexZ everything works.
This solution is not ideal though as the database table is Z_INDEX and that has a specific meaning when talking about layering of graphics.
Yes there is a bug but there is a simple workaround, please try :
displayLayerRepository.findAll(Sort.by(Sort.Order.desc("zIndex").ignoreCase()));
I suppose DisplayLayerRepository extends JpaRepository.
It's similar when you use parameters in your findBy method. Define in your repository empty method :
public List<DisplayLayer> findByDisplayContainerId(Long pDisplayLayerId, Sort sort);
Then you can call it by :
displayLayerRepository.findByDisplayContainerId(1L, Sort.by(Sort.Order.desc("zIndex").ignoreCase()));
You can use JpaSort in query. As in your case, it looks something like this:
Sort sort = JpaSort.unsafe(Sort.Direction.ASC, "zIndex");
List<DisplayLayer> zIndexes = displayLayerRepository.findByZIndex(pZIndex, sort);
and your query in Repository will look like this:
public List<DisplayLayer> findByZIndex(Long pZIndex, Sort sort);
is it possible to have a projection with nested collection with Spring JPA?
I have the following 2 simple entity (to explain the problem)
#Entity
#Table(name = "person")
public class Person implements Serializable {
private Integer id;
private String name;
#OneToMany
private List<Address> addressList = new ArrayList<>();
}
#Entity
#Table(name = "address")
public class Address implements Serializable {
private Integer id;
private String city;
private String street;
}
Is it possible to have a projection of Person with following attributes filled in ? {person.name, address.city}
I might be wrong in semantics of word Projection. but the problem is what i need to achieve. Maybe it is not possible with Projection, but is there another way to achieve the end goal? Named Entity graph perhaps ?
P.S. please suggest a solution for Spring JPA not Spring Jpa REST
thanks in advance
You're right, Entity Graphs serve this exact purpose - control field loading.
Create entity graphs dynamically from the code or annotate target entities with Named Entity Graphs and then just use their name.
Here is how to modify your Person class to use Named Entity Graphs:
#Entity
#Table(name = "person")
#NamedEntityGraph(name = "persion.name.with.city",
attributeNodes = #NamedAttributeNode(value = "addressList", subgraph = "addresses.city"),
subgraphs = #NamedSubgraph(name = "addresses.city", attributeNodes = #NamedAttributeNode("city")))
public class Person implements Serializable {
private Integer id;
private String name;
#OneToMany
private List<Address> addressList;
}
And then when loading your person:
EntityGraph graph = em.getEntityGraph("person.name.with.city");
Map hints = new HashMap();
hints.put("javax.persistence.fetchgraph", graph);
return em.find(Person.class, personId, hints);
The same applies for queries, not only em.find method.
Look this tutorial for more details.
I think that that's not usual scenario of Data JPA usage. But you can achieve your goal with pure JPQL:
SELECT a.street, a.person.name FROM Address a WHERE …
This solution has 2 drawbacks:
It forces you to have bidirectional relationship Address ←→ Person
It returns List
Another solution (and that's preferred JPA way) is to create DTO like this:
class MyPersonDTO {
private String personName;
private List<String> cities;
public MyPersonDTO(String personName, List<Address> adresses) {
this.personName = personName;
cities = adresses
.stream()
.map(Address::getCity)
.collect(Collectors.toList());
}
}
And the execute JPQL query like this:
SELECT NEW package.MyPersonDTO(p.name, p.addressList) FROM Person p WHERE …
Return type will be List<MyPersonDTO> in that case.
Of course you can use any of this solutions inside #Query annotation and it should work.
I'm trying to get a page of a partial entity (NetworkSimple) using the new feature of spring data, projections
I've checked the documentation and if I request only:
Collection<NetworkSimple> findAllProjectedBy();
It works, but if I'm using pageable:
Page<NetworkSimple> findAllProjectedBy(Pageable pageable);
It throws an error:
org.hibernate.jpa.criteria.expression.function.AggregationFunction$COUNT cannot be cast to org.hibernate.jpa.criteria.expression.CompoundSelectionImpl
Any one has already work with this ?
My NetworkSimple class is the following:
public interface NetworkSimple {
Long getId();
String getNetworkName();
Boolean getIsActive();
}
Note: This feature should work in the way described by the original poster but due to this bug it didn't. The bug has been fixed for the Hopper SR2 release, if you're stuck on an earlier version then the workaround below will work.
It is possible to use Pageable with the new query projection features introduced in Spring Data JPA 1.10 (Hopper). You will need to use the #Query annotation and manually write a query for the fields you require, they must also be aliased using AS to allow Spring Data to figure out how to project the results. There is a good example in spring-boot-samples part of the spring boot repository.
In your example it would be quite simple:
#Query("SELECT n.id AS id, n.name AS networkName, n.active AS isActive FROM Network n")
Page<NetworkSimple> findAllProjectedBy(Pageable pageable);
I have made the assumption that your entity looks something like this:
#Entity
public class Network
{
#Id
#GeneratedValue
private Long id;
#Column
private String name;
#Column
private boolean active;
...
}
Spring Data will derive a count query automatically for the paging information. It is also possible to make use of joins in the query to fetch associations and then summarise them in the projection.
I think you need create findAllProjectedBy() as specification.Then you can use findAll() method like this.
example :findAll(findAllProjectedBy(),pageable)
Following link may be help to find how to create specification in spring.
https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/
The issue may come from the method name. The by keyword means that you ae filterig data by a specific property: findByName for example. Its called query creation from method name:
http://docs.spring.io/spring-data/jpa/docs/1.10.1.RELEASE/reference/html/#repositories.query-methods.query-creation
So try with Page<NetworkSimple> findAll(Pageable pageable);
Even with spring-data-jpa 1.11.4, something like
public interface NetworkRepository extends JpaRepository<Network, String> {
Page<NetworkSimple> findAll(Pageable pageable);
}
would not compile; reporting
findAll(org.springframework.data.domain.Pageable) in NetworkRepository clashes with findAll(org.springframework.data.domain.Pageable) in org.springframework.data.repository.PagingAndSortingRepository
return type org.springframework.data.domain.Page<NetworkSimple> is not compatible with org.springframework.data.domain.Page<Network>
The workaround we found was to rename findAll to findAllBy, e.g.
public interface NetworkRepository extends JpaRepository<Network, String> {
Page<NetworkSimple> findAllBy(Pageable pageable);
}
You can use interface projection with Pageable like this :
Page<NetworkSimple> findPagedProjectedBy(Pageable pageable);
with some parameter :
Page<NetworkSimple> findPagedProjectedByName(String name, Pageable pageable);
Implementing interface projection with pagination
1. Our ResourceEntity.java class
#Getter
#Setter
#NoArgsConstructor
#Entity
public class ResourceEntity{
private Long id;
private String name;
}
2. Creating projection Interface name ProjectedResource.java, which maps data collected by the SQL query from repository layer method
public interface ProjectedResource {
Long getId();
String getName();
String getAnotherProperty();
}
3. Creating Repository layer method: getProjectedResources()
We are considering the database table name is resource.
We are only fetching id and name here.
#Query(name="select id, name, anotherProperty from resource", countQuery="select count(*) from resource", nativeQuery=true)
Page<ProjectedResource> getProjectedResources(Pageable page);
Hope the issue will be resolved!
You can use:
#Query("SELECT n FROM Network n")
Page<? extends NetworkSimple> findAllProjectedBy(Pageable pageable);