I have a User entity something like below
#Node("User")
#Data
#Builder
#AllArgsConstructor
#NoArgsConstructor
public class User {
#Id
private String id;
private String title;
#Relationship(type = "MANAGER", direction = INCOMING)
private List<User> subordinates = new ArrayList<>();
}
when a user queries he will get his data and his subordinates data and this use case working fine. But in this graph I have a requirement . The user may need his immediate manager data (may be complete data or just the name)
If I add like this , this fails as it will spirally go for Manager's manager and so on . I want only immediate manager
#Relationship(type = "MANAGER", direction = OUTGOING)
private User manager;
I want to know how to model this entity to get just manager id using Relationship.
#Relationship(type = "MANAGER", direction = OUTGOING)
private String managerId;
The second one is important for me. Can someone please help?
I tried as mentioned in above step 1 and it is failing and I understand why it is failing . Why I do not know is how to model the entity to achieve my use case.
I am using springboot 2.7.3 and spring-boot-starter-data-neo4j and neo4j 4.4.9
Related
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);
Hey everyone I am fairly new to Neo4j and am having an issue querying my repositories.
Repository is the follow:
public interface NodeOneRepository extends GraphRepository<NodeOne> {
List<NodeOne> findByNodeTwoNodeThreeAndActiveTrue(NodeThree nodeThree);
}
My entities are the following:
#NodeEntity(label = "NodeOne")
public class NodeOne {
#GraphId
private Long id;
private Boolean active = TRUE;
#Relationship(type = "IS_ON")
private NodeTwo nodeTwo;
}
#NodeEntity(label = "NodeTwo")
public class NodeTwo {
#GraphId
private Long id;
#Relationship(type = "CONTAINS", direction = "INCOMING")
private NodeThree nodeThree;
#Relationship(type = "IS_ON", direction = "INCOMING")
private List<NodeOne> nodeOnes = new ArrayList<>();
}
#NodeEntity(label = "NodeThree")
public class NodeThree {
#GraphId
private Long id;
#Relationship(type = "CONTAINS")
private List<NodeTwo> nodeTwos = new ArrayList<>();
}
Getters & Setters omitted. When I call the method I get an empty list. Is there something I am doing incorrectly?
You didn't describe exactly what you wanted to achieve, but I can see two problems:
Problem 1:
The current version of Spring Data Neo4j and OGM only allow nested finders, that is, finders that specify a relationship property, to one depth.
Supported
findByNodeTwoSomePropertyAndActiveTrue(String relatedNodePropertyValue)
Not Supported
findByNodeTwoNodeThree //Nesting relationships in finders is not supported
Problem 2:
Derived Finders Allow Matching Properties and Nested Properties. Not a whole instance of that class.
You can probably achieve what you would like using a custom query.
#Query("custom query here")
List<NodeOne> findByNodeTwoNodeThreeAndActiveTrue(NodeThree nodeThree);
If you need help to write a custom query, you can post another question or join the neo4j-users public slack channel.
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 seem to be baffled on how JPA Repositories are suppose to work.
In a nut-shell
#Entity
public class User extends AbstractEntity {
protected final static String FK_NAME = "USER_ID";
#Column(nullable = false)
private String firstName;
#OneToMany(cascade = ALL, fetch = FetchType.LAZY, orphanRemoval = true)
#JoinColumn(name = "userId")
private List<Detail> details = new ArrayList<Detail>();
}
#Entity
public class Detail extends AbstractEntity {
Long userId;
String hello;
}
#Repository
public interface UserRepository extends CrudRepository<User, Long> {
User findByFirstName(#Param("firstName") String firstName);
}
And here is the only controller in the app:
#RestController
public class Home {
#Autowired
UserRepository userRepository;
#Autowired
DetailsRepository loanRepository;
#RequestMapping(value = "")
public HttpEntity home() {
User user = userRepository.findByFirstName("John");
if (user == null) {
user = new User();
user.setFirstName("John");
}
Detail detail = new Detail();
detail.setHello("Hello Msh");
user.getDetails().add(detail);
userRepository.save(user);
return new ResponseEntity("hi", HttpStatus.OK);
}
}
Below a screenshot from debugging session where the app just started and the get request to home() method creates new user, new detail, adds detail to user.
Below example - when the user is saved, the detail entity gets updated
Now on the next request, the old user John is found and has been added a new instance of detail.
The old user has been saved but now the newly created detail does not get updated outside.
How come this only works first time ?
Basically theres so much fail going on so that I would advise you to go a step backwards. If youre wana go the short path of getting a solution for exactly this problem continue reading ;)
First part related to the answer of Jaiwo99:
As I can see in the gradle view of intellij, your using Spring Boot. So it is necessary to place #EnableTransactionManagement on top of your configuration class. Otherwise the #Transacion annotation does not have any effect.
Second part your JPA/Hibernate model mapping. Theres so much bad practise on the net that it is no wonder that most beginners have troubles starting with it.
A correct version could look like (not tested)
#Entity
public class User extends AbstractEntity {
#Column(nullable = false)
private String firstName;
#OneToMany(cascade = ALL, fetch = FetchType.LAZY, orphanRemoval = true, mappedBy="user")
private List<Detail> details = new ArrayList<Detail>();
public void addDetail(Detail detail) {
details.add(detail);
detail.setUser(user);
}
}
#Entity
public class Detail extends AbstractEntity {
#ManyToOne
private User user;
private String hello;
public void setUser(User user){
this.user = user;
}
}
Some general advice related to creating a model mapping:
avoid bi-directional mappings whenever possible
cascade is a decision made on the service level and not at the model level and can have huge drawbacks. So for beginners avoid it.
I have no idea why people like to put JoinColumn, JoinTable and whatever join annotation on top of fields. The only reason to do this is when you have a legacy db (my opinion). When you do not like the names created by your jpa provider, provide a different naming strategy.
I would provide a custom name for the user class, because this is in some databases a reserved word.
Very simple, the first time you saved a new entity outside of hibernate session, the second time, the user object you got is a detached object, by default hibernate will not consider it is changed in this case.
*solution *
Move this logic to another service class, which annotated with #transactional
Or
Annotate your controller with transactional
Or
Override equals and hashCode method on user class may also help
I am trying to find a way to retrieve the auto generated Id of an entity that is persisted in the database via cascade. I am using Hibernate 4.1.9, Spring data 1.2 and Spring framework 3.2.1. Here are the entities in question : Location, Home, Room.
Location parent class
#Entity
#Table(name = "location")
#Inheritance(strategy = InheritanceType.JOINED)
public class Location implements Serializable
{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "location_id", unique = true)
private long uuid;
// other attributes and methods not relevant
}
Home class extending a Location, referencing a set of Rooms
#Entity
#Table(name = "home")
#Inheritance(strategy = InheritanceType.JOINED)
#PrimaryKeyJoinColumn(name = "home_id")
public class Home extends Location implements Serializable
{
#OneToMany(mappedBy = "containingHome", cascade = {CascadeType.ALL}, orphanRemoval = true)
private Set<Room> rooms;
// other attributes and methods not relevant
}
and finally the Room class referencing a Home object
#Entity
#Table(name = "room")
#PrimaryKeyJoinColumn(name = "room_id")
public class Room extends Location implements Serializable
{
#ManyToOne()
#JoinColumn(name = "home_id")
protected Home containingHome;
// other attributes and methods not relevant
}
I am using Spring data to create Repositories for the entities.
LocationRepository
public interface LocationRepository extends JpaRepository<Location, Long>
{ }
The problem I am having is that I need the id in order to be able to retrieve the different objects from the database and that is generated automatically. The only way I can access the id through the element is if I get the managed object when I save it to the database. But if I try to save each location in turn like so:
Home home = new Home();
home = locationService.save(home) // service that just calls locationRepository.save method
Room bedroom = new Room(home);
bedroom = locationService.save(bedroom);
I get a duplicate entry of room in the database which I think is related to a Hibernate issue https://hibernate.onjira.com/browse/HHH-7404. If I just call
Home home = new Home();
Room bedroom = new Room(home);
locationService.save(home)
there are no doubles but I have no way to retrieve the room object since it was persisted on cascade and its id is 0. Is there a way to solve this without introducing other fields in the location like a unique name that I have to generate myself? Any help is much appreciated.
Edit
If in the last case I have home = locationService.save(home) and then call home.getUuid() I get the right value which is normal I think since I retrieve a managed object. But if I do bedroom.getUuid() I get 0 since bedroom is not managed and so it has not had its id field updated with the value from the database.
Have you tried calling home.getUuid(); (assuming you have a getter for that field) after the persist call?
You might be surprised, but Hibernate (and JPA) will update the in memory copy with the id.