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ManyToOne referenced entities not exist in JSON Response when returning PagedResource

When I return a Page<Entity> from a method inside my #RestController class, all fields of Entity both referenced via #OneToXXX and #ManyToXXX take place in the returned JSON object. But when I switched the return type to PagedResource (to be able to add links to the response), #ManyToXXX fields are not included at all.
Here is the method in question:
#GetMapping("/fetch")
public PagedResources getResults(Pageable pageable, PagedResourcesAssembler assembler) {
Page<ParentClass> page = myRepository.findAll(pageable);
PagedResources pagedResources = assembler.toResource(page, myResourceAssembler);
return pagedResources;
}
Here is the resource assembler: it's #Autowired in the MyController's body.
MyResourceAssembler
#Component
public class MyResourceAssembler extends ResourceAssemblerSupport<ParentClass, Resource> {
public MyResourceAssembler() { super(MyController.class, Resource.class); }
#Override
public Resource toResource(ParentClass obj) {
return new Resource<>(obj,
linkTo(methodOn(MyController.class).getResults(obj.getId())).withRel("edit"),
}
}
Here are the basic class definitions:
ParentClass
#Entity
#Table(name = "parent_table", catalog = "myDB")
public class ParentClass implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Integer id;
#ManyToOne(optional = false)
#JoinColumn(name = "other_class", referencedColumnName = "id")
private OtherClass otherClass;
#OneToOne(mappedBy = "parent")
private SampleField1 sampleField1;
#OneToMany(mappedBy = "parent")
private List<SampleField2> sampleField2;
}
SampleField1 OneToXXX
#Entity
#Table(name = "sample_table_1", catalog = "myDB")
public class SampleField1 implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Integer id;
#Column(name="some_field")
String someField;
#OneToOne
#JoinColumn(name = "sample_field_1", referencedColumnName = "id")
#JsonBackReference //to avoid infinite recursion
private ParentClass parent;
}
OtherClass ManyToOne
#Entity
#Table(name = "other_table", catalog = "myDB")
public class OtherClass implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id", nullable = false)
private Integer id;
#Column(name="some_other_field")
String someOtherField;
// I don't need any reference to ParentClass here.
}
To add further detail to the issue here is the logging output of changeProperties() method inside PersistentEntityJackson2Module class:
s.d.r.w.j.PersistentEntityJackson2Module : Assigning nested entity serializer for #javax.persistence.OneToOne(..) com.project.SampleField1 com.project.model.ParentClass.sampleField1
s.d.r.w.j.PersistentEntityJackson2Module : Assigning nested entity serializer for #javax.persistence.OneToMany(..) com.project.SampleField2 com.project.model.ParentClass.sampleField2
// .... omitted other lines for brevity
the resulting JSON is :
{
"_embedded":{
"parentClasses":[
{
"id":1,
// <-- There is no field for otherClass !
"sampleField1":{
"id":1,
"sampleField":"blabla"
},
"sampleField2":[ ]
}
]
},
"links":[
]
}
As it can be seen above, OneToXXX fields are being taken to be serialized but no output for the ManyToOne fields like
Assigning nested entity serializer for #javax.persistence.ManyToOne ... com.my.OtherClass ... and therefore those aren't existed in the response JSON.
According to this SO answer, #ManyToXXX referenced entities are appended as links to the JSON response. But that's not an acceptable solution for me since I have a different planning of consumption in my mind for the rest client.
Bottomline, I'd like to have my ManyToOne referenced entities in my JSON Response returned from getResults() method.
Anything I can provide just ask in the comments.

Return Entity in responses is not the best way, because usually clients dont need whole set of data. Also, if Entities has links for each other, it will cause StackoverflowException on serialization tries. Use DTO for responses. At least it will help you to determine where is the problem - serialization, or fetching from database. Anyway it is more proper way for serving data to clients.
By the way, check getter and setter for otherClass in your ParentClass :) If threre is no getter and setter, thats will be reason of your issue.
Also, take a look into OtherClass for default empty constructor. If it hasn't present in there, you should add it.

One-To-Many relation in JPA DELETE operation is not working

The entity model and repository is given below.
Channel.java
public class Channel extends BaseEntity implements Serializable {
private static final long serialVersionUID = 1L;
#Column(name = "channel_name")
private String channelName;
#Column(name = "channel_type")
private Integer channelType;
#Column(name = "seq_id")
private Integer seqId;
#Column(name = "channel_device_key")
private String channeldeviceKey;
}
UserRoomChannel.java
public class UserRoomChannel extends BaseEntity implements Serializable {
private static final long serialVersionUID = 1L;
#OneToOne
#JoinColumn(name = "user_house_id")
private UserHouse userHouse;
#OneToOne
#JoinColumn(name = "room_id")
private Room room;
#LazyCollection(LazyCollectionOption.FALSE)
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
private List<Channel> channels;
}
UserRoomChannelReposirtory.java
public interface UserRoomChannelRepository extends JpaRepository<UserRoomChannel, Long> {
#Query(value = "DELETE FROM user_room_channel_channels WHERE channels_id=?1", nativeQuery = true)
void deleteUserRoomChannelChannels(Long id);
}
I can save the data successfully. When data is saved through this a third table named user_room_channel_channels is created.
EX:
user_room_channel_id channels_id
1 1
1 2
But When I tried to delete with channels_id it give me the error
A collection with cascade="all-delete-orphan" was no longer referenced by the owning entity instance:.....
The native query what I write it execute from the command line.
But using JPA I can't do that.
Any help or any suggestion for resolving this issue?

A collection with cascade="all-delete-orphan" was no longer referenced
by the owning entity instance
is because before you delete your channels(and its children), you somehow do the following:
you load your UserRoomChannel along with its Channels children in the collection from the Database.
somewhere in your code you change the reference of the children collection : myUserRoomChannel.setChannels(newChannelCollections) or myUserRoomChannel.channels =new ChannelCollections();
and you try to delete the user with your repositorisory.
Hibernate who remembered having set the children collection with reference A to the User can find the collection anymore, because User.channels is now User.channels == B (with B being a new reference to your collection).
How to fix it:
just find the place where you are replacing your children collections and instead of:
myUserRoomChannel.setChannels(newChannelCollections), or
myUserRoomChannel.channels =new ChannelCollections(),
just do
myUserRoomChannel.getChannels().add/delete/clearYourChannels()

I just have done the below step and it works perfectly.
Reomve:
myUserRoomChannel.setChannels(channels)
Add
myUserRoomChannel.getChannels().removeAll(channels) and then
userRoomChannelRepository.save(myUserRoomChannel)

PSQLException: ERROR: syntax error at or near

I have what I thought was a straight forward relation in JPA. Looks like this. CompanyGroup:
#Entity
#Table
public class CompanyGroup implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue
private Long id;
#Column(name = "name")
private String name;
#JoinColumn(name = "companies")
#OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<Company> companies;
}
Company:
#Entity
#Table
public class Company implements Serializable {
private static final long serialVersionUID = 1L;
#Column(name = "name")
private String name;
#JoinColumn(name = "users")
#OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<User> users;
#Id
#GeneratedValue
private Long id;
}
User:
#Entity
#Table
public class User {
#Column(name = "firstName")
private String firstName;
#Column(name = "lastName")
private String lastName;
#Column(name = "email")
private String email;
#Id
#GeneratedValue
private Long id;
}
I have omitted setters, getters, etc.
This is not working. I'm trying to save a CompanyGroup(Has 2 companies, each company has 2 users, all entities are unique) to a fully empty database.
I persist this using Spring-Data, accessed in a service like this:
#Service
public class ConcreteCompanyGroupService implements CompanyGroupService {
#Autowired
private CompanyGroupRepository repository;
#Transactional
#Override
public void save(CompanyGroup group) {
repository.save(Collections.singleton(group));
}
}
When I try to call this method I receive this:
org.postgresql.util.PSQLException: ERROR: syntax error at or near "User"
Position: 13
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2458)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2158)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:291)
Hopefully I have done something stupid that someone can find quickly. I don't know how to solve this.
EDIT:
The driver in my pom.xml:
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>9.4.1211</version>
</dependency>

Your entity maps across to a table name that is an SQL reserved keyword (User). Sadly for you, your chosen JPA provider does not automatically quote the table name identifier, and so you get exceptions when referring to the table.
Solution is either to quote the table name yourself in the #Table annotation, or change the table name to not be a reserved keyword. Alternatively use a JPA provider that auto-quotes such reserved keywords for you (e.g DataNucleus)

Solution 1: As Pascal mentioned, you have to escape the table name with backslash like:
#Entity
#Table(name="\"User\"")
public class User {
...
}
Solution 2: Rename your table's anme with another name (Users)
#Entity
#Table(name="Users")
public class User {
...
}
Solution 3: Add a suffix to the table's name:
#Entity
#Table(name="APP_User")
public class User {
...
}
Solution 4: Change the entity name, e.g. ApplicationUser
#Entity
public class ApplicationUser {
...
}
The reason
PostgreSQL as some reserved SQL Key Words. For example: ABORT, ALL, ARRAY, CACHE, CUBE, USER, ... Those tokens are in the SQL standard or specific to PostgreSQL

Use the #Table annotation or change your class name from User to something else as User is a reserved keyword in sql.

Spring query distinct on a entire object

I'm using spring data and I made this query:
#Query("SELECT DISTINCT u.pk.fleet.fleetName FROM FleetHasUser u WHERE u.pk.user.username = ?1")
List<FleetName> allFleetNameForUser(String username);
The aim of this query is find all FleetName for a specific user.
This is the part of database schema interested in:
The FleetHasUser class:
#Entity
#Table(name = "fleet_has_user", catalog = "dart")
#AssociationOverrides({
#AssociationOverride(name = "pk.user",
joinColumns = #JoinColumn(name = "id_username")),
#AssociationOverride(name = "pk.fleet",
joinColumns = #JoinColumn(name = "id_fleet")) })
public class FleetHasUser implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private FleetHasUserKeys pk = new FleetHasUserKeys();
#EmbeddedId
public FleetHasUserKeys getPk() {
return pk;
}
the FleetHasUserKeys class:
#Embeddable
public class FleetHasUserKeys implements Serializable {
private static final long serialVersionUID = 1L;
protected User user;
protected Fleet fleet;
Fleet class:
#Entity
#Table(name = "fleet", catalog = "dart")
public class Fleet implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer idFleet;
private Ecu ecu;
private String application;
private Cubic cubic;
private Integer power;
private String euroClass;
private String engineType;
private Traction traction;
private String transmission;
private String note;
private FleetName fleetName;
#JsonIgnore
private Set<Car> cars = new HashSet<Car>(0);
#JsonIgnore
private Set<FleetHasUser> fleetHasUsers = new HashSet<FleetHasUser>(0);
As you can see FleetName is a class. I tried without distinct and the list had duplicated elements, so before create a subquery I inserted distinct only for test and it worked. I didn't find information on google, but is it possible to use distinct on a object? How does it work(check the primary key fields)?
Maybe may I even create a Spring data query like findDistinctPkFleetFleetNameByPkUserUsername?
Thanks

As far as i know, the distinct is being applied on the query not on the mapping phase, as you can see #Query doc the annotation only executes jpql queries so a native distinct.
As you say other option to execute a distinct is
Spring data Distinct
You cannot apply "Distinct" to objects, but you can map then on Set's to avoid duplicated, but the better approach is filter properly the data on the database.

Hibernate. Repeated column when mapping #IdClass annotated entity with composite key

I've ran into problem with composite primary key handling by Hibernate as a JPA provider.
My entities look like below
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#Column(name = "place_id")
private Integer placeId;
#Id
#Column(name = "external_object_id")
private Integer externalObjectId;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Integer placeId;
private Integer externalObjectId;
}
Looks pretty simple yet no matter what I do I keep getting the following exception (lines are splitted for readability):
org.hibernate.MappingException:
Repeated column in mapping for entity: ExternalMatch
column: external_object_id (should be mapped with insert="false" update="false")
I've tried placing annotation on entity class fields and key class fields together as well as separately, moving all annotations from fields to getters on each one of the classes, using key calss as #Embeddable and putting it into the entity class with #EmbeddedId. Nothing seems to work.
This case seems trivial so maybe it's something wrong with our setup but I can't even imagine where to look for the issue.
Any advice is much appreciated.

It appears that I shot myself in the foot with this.
The issue was that I had a biderectional mapping between ExternalMatch and ExternalObject I forgot about trying to replace the actual entity with its integer id.
So changing
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#Column(name = "place_id")
private Integer placeId;
#Id
#Column(name = "external_object_id")
private Integer externalObjectId;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Integer placeId;
private Integer externalObjectId;
}
// Related entity class
#Entity
#Table(name = "external_object")
public class ExternalObject extends AbstractNameableEntity {
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
#JoinColumn(name = "external_object_id", nullable = false)
private List<ExternalMatch> matches;
// ...
}
to reprsent actual mappings like this
// Entity class
#Entity
#IdClass(ExternalMatchPK.class)
#Table(name = "external_match")
public class ExternalMatch {
#Id
#ManyToOne
#JoinColumn(name = "external_object_id", referencedColumnName = "id")
private ExternalObject externalObject;
#Id
#ManyToOne
#JoinColumn(name = "place_id")
private Poi place;
// ... Other stuff here
}
// Key class
public class ExternalMatchPK implements Serializable {
private Poi place;
private ExternalObject externalObject;
}
// Related entity class
#Entity
#Table(name = "external_object")
public class ExternalObject extends AbstractNameableEntity {
#OneToMany(cascade = CascadeType.ALL, mappedBy = "externalObject")
private List<ExternalMatch> matches;
// ...
}
resolved the repeated mapping issue yet leaving us with all the familiar troubles a biderectional mapping creates :)