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Deleting association between two objects

I create application in Spring, which stores albums, musicians and bands. Album can contain multiple bands and musicians. I created association between Album and Band/Musician. Jet I am unable to delete it. I don't want to delete objects, just the association. I tried to send REST PUT request and setting musicians and bands to null on Album site, yet nothing happens:
{
"id": 2,
"title": "Lulu",
"bands": null,
"musicians": null,
"duration": {
"hours": 1,
"minutes": 20,
"seconds": 4
},
"releaseDate": "31/10/2011",
"coverPath": "https://upload.wikimedia.org/wikipedia/en/4/40/Lou_Reed_and_Metallica_-_Lulu.jpg",
"spotifyPath": null
}
I have created following class and method to link Album and Musician, yet I am unable to "unlink" them:
#RestController
public class AlbumMusicianController {
#Autowired
AlbumRepository albumRepository;
#Autowired
MusicianRepository musicianRepository;
#Transactional
#PostMapping("/musician/{musicianId}/album/{albumId}")
public List<Album> associate(#PathVariable Long musicianId, #PathVariable Long albumId) {
Album album = this.albumRepository.findById(albumId).orElseThrow(() -> new MissingResourceException("Album",
"Album", albumId.toString()));
return this.musicianRepository.findById(musicianId).map((musician) -> { musician.getAlbums().add(album);
return this.musicianRepository.save(musician).getAlbums();
}).orElseThrow(() -> new MissingResourceException("Musician", "Musician", musicianId.toString()));
}
}
Would be thankful for any help.
Below are necessary sources.
Album class:
#Entity
#Table(name="album")
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Album {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name="title")
private String title;
#ManyToMany(targetEntity = Band.class, mappedBy = "albums")
#JsonSerialize(using = BandsSerializer.class)
private List<Band> bands;
#ManyToMany(targetEntity = Musician.class, mappedBy = "albums")
#JsonSerialize(using = MusiciansSerializer.class)
private List<Musician> musicians;
#Embedded
#Column(name="duration")
private Duration duration;
#Column(name="releasedate")
#JsonFormat(shape=JsonFormat.Shape.STRING, pattern="dd/MM/yyyy", timezone="CET")
private Date releaseDate;
#Column(name="coverpath")
private String coverPath;
#Column(name="spotifypath")
private String spotifyPath;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public Duration getDuration() {
return duration;
}
public void setDuration(Duration duration) {
this.duration = duration;
}
public Date getReleaseDate() {
return releaseDate;
}
public void setReleaseDate(Date releaseDate) {
this.releaseDate = releaseDate;
}
public String getCoverPath() {
return coverPath;
}
public void setCoverPath(String coverPath) {
this.coverPath = coverPath;
}
public String getSpotifyPath() {
return spotifyPath;
}
public void setSpotifyPath(String spotifyPath) {
this.spotifyPath = spotifyPath;
}
public List<Band> getBands() {
return bands;
}
public void setBands(List<Band> bands) {
this.bands = bands;
}
public List<Musician> getMusicians() {
return musicians;
}
public void setMusicians(List<Musician> musicians) {
this.musicians = musicians;
}
}
Musician class:
#Entity
#Table(name="musician")
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Musician {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name="name")
private String name;
#Column(name="surname")
private String surname;
#Column(name="birthdate")
#JsonFormat(shape=JsonFormat.Shape.STRING, pattern="dd/MM/yyyy", timezone="CET")
private Date birthDate;
#Column(name="picturepath")
private String picturePath;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "album_musician",
joinColumns = #JoinColumn(name = "album_id", referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "musician_id",
referencedColumnName = "id"))
private List<Album> albums;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSurname() {
return surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
public Date getBirthDate() {
return birthDate;
}
public void setBirthDate(Date birthDate) {
this.birthDate = birthDate;
}
public String getPicturePath() {
return picturePath;
}
public void setPicturePath(String picturePath) {
this.picturePath = picturePath;
}
public List<Album> getAlbums() {
return albums;
}
public void setAlbums(List<Album> albums) {
this.albums = albums;
}
}
Band class:
#Entity
#Table(name="band")
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Band {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
#Column(name="name")
private String name;
#Column(name="picturepath")
private String picturePath;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "album_band",
joinColumns = #JoinColumn(name = "album_id", referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "band_id",
referencedColumnName = "id"))
#JsonSerialize(using = AlbumsSerializer.class)
private List<Album> albums;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPicturePath() {
return picturePath;
}
public void setPicturePath(String picturePath) {
this.picturePath = picturePath;
}
public List<Album> getAlbums() {
return albums;
}
public void setAlbums(List<Album> albums) {
this.albums = albums;
}
}

Based on your JSON body I'm going to assume you were sending a PUT request for the Album entity. There were two things that I found missing that got it to work for me after adjusting. I'm not sure if you were avoiding using them for one reason or another.
Cascade rules to cascade changes from Album to its relations.
Proper entity mapping for the join table from Album to its relations.
Not really sure why this was an issue - Hibernate did not seem to throw any exceptions related to this at execution time, but it did not seem to persist things correctly.
Here is an adjusted relation definition for Album's relation to Musician.
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name="album_musician", joinColumns = #JoinColumn(name = "musician_id", referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "album_id",
referencedColumnName = "id"))
private List<Musician> musicians;
In this format, I was able to cascade changes from Album to Musician. You will have to do something similar for the Band entity to cascade operations from Album to Band.

Can't left join a second table

I am trying to left join a second table but it doesn't show up. It just gives me all users instead of all users along with the FinishedExams.
This is the method in my repository:
public interface IUserRepository extends CrudRepository<User, Integer> {
#Query("SELECT u FROM User u LEFT JOIN FinishedExam f ON u.id = f.user")
List<User> getAllWithExams();
}
In my FinishedExamController:
#Autowired
private IFinishedExamRepository finishedExamRepository;
#Autowired
private IUserRepository userRepository;
#GetMapping("/allUsersWithExams")
#Fetch(FetchMode.SELECT)
public Iterable<User> getAllUsersWithTheirExams()
{
return userRepository.getAllWithExams();
}
My User model:
#Entity
#Table(name = "users")
public class User implements Serializable {
#Id
#GeneratedValue()
#Column(name = "id")
private int id;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "role_id", nullable = false)
public Role role;
public String getStudentNumber() {
return studentNumber;
}
public void setStudentNumber(String studentNumber) {
this.studentNumber = studentNumber;
}
#Column(name = "student_number", nullable = true)
private String studentNumber;
#Column(name = "first_name", nullable = true)
private String firstName;
#Column(name = "last_name", nullable = true)
private String lastName;
#Column(name = "email", nullable = true, unique = true)
private String email;
#OneToOne(fetch = FetchType.EAGER, mappedBy = "user")
private FinishedExam finishedExam;
#JsonIgnore
#Column(name = "password", nullable = true)
private String password;
#Column(name = "created_at")
private LocalDateTime createdAt;
#Column(name = "updated_at")
private LocalDateTime updatedAt;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(
name = "event_users",
joinColumns = #JoinColumn(name = "user_id", referencedColumnName = "id"),
inverseJoinColumns = #JoinColumn(name = "event_id", referencedColumnName = "id")
)
#PreUpdate
protected void onUpdate() {
updatedAt = LocalDateTime.now();
}
#PrePersist
protected void onCreate() {
createdAt = LocalDateTime.now();
updatedAt = createdAt;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public LocalDateTime getCreatedAt() {
return createdAt;
}
public void setCreatedAt(LocalDateTime createdAt) {
this.createdAt = createdAt;
}
public LocalDateTime getUpdatedAt() {
return updatedAt;
}
public void setUpdatedAt(LocalDateTime updatedAt) {
this.updatedAt = updatedAt;
}
public String getRole() {
return role.getName();
}
public void setRole(Role role) {
this.role = role;
}
}
Finished exams model:
#Entity
#Table(name = "finished_exams")
public class FinishedExam implements Serializable {
#Id
#GeneratedValue()
#Column(name = "id")
private int id;
#OneToOne(fetch = FetchType.EAGER)
#Fetch(FetchMode.SELECT)
#JoinColumn(name = "user_id")
private User user;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "exam_id")
private Exam exam;
#Column(name = "finishedExam", nullable = false)
private String finishedExam;
#Column(name = "created_at")
private LocalDateTime createdAt;
#Column(name = "updated_at")
private LocalDateTime updatedAt;
#PrePersist
protected void onCreate() {
createdAt = LocalDateTime.now();
updatedAt = createdAt;
}
#PreUpdate
protected void onUpdate() {
updatedAt = LocalDateTime.now();
}
public int getId() {
return id;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Exam getExam() {
return exam;
}
public void setExam(Exam exam) {
this.exam = exam;
}
public String getFinishedExam() {
return finishedExam;
}
public void setFinishedExam(String finishedExam) {
this.finishedExam = finishedExam;
}
public void setId(int id) {
this.id = id;
}
public LocalDateTime getCreatedAt() {
return createdAt;
}
public void setCreatedAt(LocalDateTime createdAt) {
this.createdAt = createdAt;
}
public LocalDateTime getUpdatedAt() {
return updatedAt;
}
public void setUpdatedAt(LocalDateTime updatedAt) {
this.updatedAt = updatedAt;
}
}
I can put whatever I want in the ON clause but nothing changes.

You need to provide a path from your entity to target entity to join:
Replace the query
#Query("SELECT u FROM User u LEFT JOIN FinishedExam f ON u.id = f.user")
with
#Query("SELECT u FROM User u LEFT JOIN u.finishedExam f ON u.id = f.user.id")

I can put whatever I want in the ON clause but nothing changes.
Of course nothing changes. You are performing a left join across a 1:1 relationship, selecting (only) the left entity, and not placing any filter criteria on that entity. The join criteria (and indeed the join itself) don't matter: your query is equivalent to SELECT u FROM User u.
Did you perhaps mean to perform an inner join instead?

Referenced entities in Hibernate are null after parent objects are persisted

I have 2 entity classes like below. After the parent object is persisted,
accessing the foreign key referenced object returns null.The entity classes are as below.
I have an Employee entity class like below
#Entity
#Table(name = "employees")
public class Employee {
private long employeeId;
private String name;
private long companyId;
private Company companyByCompanyId;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "employee_id")
public long getEmployeeId() {
return employeeId;
}
public void setEmployeeId(long employeeId) {
this.employeeId = employeeId;
}
#Basic
#Column(name = "name")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#Basic
#Column(name = "company_id")
public long getCompanyId() {
return companyId;
}
public void setCompanyId(long companyId) {
this.companyId = companyId;
}
#ManyToOne
#JoinColumn(name = "company_id", referencedColumnName = "company_id", nullable = false, insertable = false, updatable = false)
public Company getCompanyByCompanyId() {
return companyByCompanyId;
}
public void setCompanyByCompanyId(Company companyByCompanyId) {
this.companyByCompanyId = companyByCompanyId;
}
}
and a Company entity class like below
#Entity
#Table(name = "companies")
public class Company {
private long companyId;
private String companyName;
private Collection<Employee> employeesByCompanyId;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "company_id")
public long getCompanyId() {
return companyId;
}
public void setCompanyId(long companyId) {
this.companyId;
}
#Basic
#Column(name = "company_name")
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
#OneToMany(mappedBy = "companyByCompanyId")
public Collection<Employee> getEmployeesByCompanyId() {
return employeesByCompanyId;
}
public void setEmployeesByCompanyId(Collection<Employee> employeesByCompanyId) {
this.employeesByCompanyId = employeesByCompanyId;
}
}
This is the controller method in a controller class
#ApiOperation(value="Create a new employee")
#ApiResponses({})
#RequestMapping(value= "/createEmployee",method= RequestMethod.POST)
public Callable<EmployeeDTO> createEmployee(
HttpServletRequest request,
#RequestBody #Valid final List<EmployeeDTO> employeeDto) {
long employeeId = employeeService.createEmployee(employeeDto);
EmployeeDTO createdEmployee = employeeService.getEmployee(employeeId);
return () -> createdEmployee;
}
This is the method for createEmployee(employeeDto) in the service class
#Transactional
public long createEmployee(employeeDto){
Employee employee = new Employee();
employee.setName(employeeDto.getName());
employee.setCompanyId(employeeDto.getCompanyId());
Employee savedEmployee = employeeRepository.save(employee);
return savedEmployee.getEmployeeId();
}
This is the getEmployee method in the same service class as above.
public EmployeeDTO getEmployee(long employeeId) {
Employee employee = employeeRepository.findByEmployeeId(employeeId);
EmployeeDTO employeeDTO = new EmployeeDTO();
employeeDTO.setEmployeeId(employee.getEmployeeId());
employeeDTO.setName(employee.getName());
employeeDTO.setCompanyByCompanyId(employee.getCompanyByCompanyId());
}
employee.getCompanyByCompanyId() -> this is where it throws the Null pointer exception.
The companies table already has the company row that I am associating with employee.

Cycle in Hibernate OneToMany relation

I use Hibernate and
have two entities(City and Region) with OneToMany relation.
the First:
#Entity
#Table(name = "p_region")
public class Region implements Serializable{
#OneToMany(mappedBy = "region",fetch= FetchType.LAZY, cascade = CascadeType.MERGE)
private List<City> citys;
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name;
//++++++++++++++++++++ GETSET
public List<City> getCitys() {
return citys;
}
public void setCitys(List<City> citys) {
this.citys = citys;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
and the second one:
#Entity
#Table(name = "p_city")
public class City implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#NotEmpty(message = "Название не должно быть пустым")
#Length(max = 10, min = 2, message = "Название должно быть менее 2 символов и не
более 100")
private String cityName;
#NotEmpty(message = "Код города не должно быть пустым")
private String cityCode;
#Column(name = "zone")
private Integer zone;
#Basic(optional = true)
#Temporal(javax.persistence.TemporalType.TIMESTAMP)
private Date entryDate = Calendar.getInstance().getTime();
#ManyToOne()
private Region region;
#Basic(optional = true)
private String zip_code;
// GET SET ::::::::::::::::::::::::::::::::::
public Integer getZone() {
return zone;
}
public void setZone(Integer zone) {
this.zone = zone;
}
public Region getRegion() {
return region;
}
public void setRegion(Region region) {
this.region = region;
}
public void delete() {
System.out.println("QQQQQQQQQQQQQQQQQQQQQQ");
}
public String getCityCode() {
return cityCode;
}
public void setCityCode(String cityCode) {
this.cityCode = cityCode;
}
public String getCityName() {
return cityName;
}
public void setCityName(String cityName) {
this.cityName = cityName;
}
public Date getEntryDate() {
return entryDate;
}
public void setEntryDate(Date entryDate) {
this.entryDate = entryDate;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getZip_code() {
return zip_code;
}
public void setZip_code(String zip_code) {
this.zip_code = zip_code;
}
}
When I try to get simple Object(City) with JSON it returns the cycle:
{"id":577,"region":{"name":"нет региона","id":15,"citys":[{"id":577,"region":
{"name":"нет региона","id":15,"citys":[{"id":577,"region":{"name":"нет
региона","id":15,"citys":[{"id":577,"region":{"name":"нет
региона","id":15,"citys":[{"id":577,"region":{"name":"нет
региона","id":15,"citys":[{"id":577,"region":{"name":"нет
региона","id":15,"citys":[{"id":577,"region":{"name":"нет......so on.
Are there any solutions for this issue?

You need to break the bi-directional relationship between your entity before converting to JSON.
I think there are two options:
Iterate the child collection, e.g. citys in Region and set Region to null. This way, circular dependency would be broken. You my want to add one name mapped attribute regionId in the City so that relational info is still available.
Create another set of POJO objects without circular dependency, copy the values from Entity Objects and then get the JSON using POJO objects.

JPA - Get collection from ManyToOne relationship

I have a table Post and Post_Image
#Entity
#Table(name = "post")
#XmlRootElement
#NamedQueries({
#NamedQuery(name = "Post.findAll", query = "SELECT p FROM Post p"),
#NamedQuery(name = "Post.findByPostId", query = "SELECT p FROM Post p WHERE p.postId = :postId"),
#NamedQuery(name = "Post.findByTitle", query = "SELECT p FROM Post p WHERE p.title = :title"),
#NamedQuery(name = "Post.findByCreatedDatetime", query = "SELECT p FROM Post p WHERE p.createdDatetime = :createdDatetime")})
public class Post implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#NotNull
#Column(name = "post_id")
private Integer postId;
#Basic(optional = false)
#NotNull
#Size(min = 1, max = 500)
#Column(name = "title")
private String title;
#Basic(optional = false)
#NotNull
#Lob
#Size(min = 1, max = 65535)
#Column(name = "content")
private String content;
#Column(name = "created_datetime")
#Temporal(TemporalType.TIMESTAMP)
private Date createdDatetime;
#JoinColumn(name = "user_id", referencedColumnName = "user_id")
#ManyToOne(optional = false)
private User userId;
#JoinColumn(name = "post_type_id", referencedColumnName = "post_type_id")
#ManyToOne(optional = false)
private PostType postTypeId;
public Post() {
Date date = new Date();
this.createdDatetime =new Date(date.getTime());
}
public Post(Integer postId) {
this.postId = postId;
}
public Post(Integer postId, String title, String content) {
this.postId = postId;
this.title = title;
this.content = content;
}
public Integer getPostId() {
return postId;
}
public void setPostId(Integer postId) {
this.postId = postId;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public Date getCreatedDatetime() {
return createdDatetime;
}
public void setCreatedDatetime(Date createdDatetime) {
this.createdDatetime = createdDatetime;
}
public User getUserId() {
return userId;
}
public void setUserId(User userId) {
this.userId = userId;
}
public PostType getPostTypeId() {
return postTypeId;
}
public void setPostTypeId(PostType postTypeId) {
this.postTypeId = postTypeId;
}
#Override
public int hashCode() {
int hash = 0;
hash += (postId != null ? postId.hashCode() : 0);
return hash;
}
#Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof Post)) {
return false;
}
Post other = (Post) object;
if ((this.postId == null && other.postId != null) || (this.postId != null && !this.postId.equals(other.postId))) {
return false;
}
return true;
}
#Override
public String toString() {
return "entity.Post[ postId=" + postId + " ]";
}
}
and
#Entity
#Table(name = "post_image")
#XmlRootElement
#NamedQueries({
#NamedQuery(name = "PostImage.findAll", query = "SELECT p FROM PostImage p"),
#NamedQuery(name = "PostImage.findByPostImageId", query = "SELECT p FROM PostImage p WHERE p.postImageId = :postImageId"),
#NamedQuery(name = "PostImage.findByPath", query = "SELECT p FROM PostImage p WHERE p.path = :path"),
#NamedQuery(name = "PostImage.findByTitle", query = "SELECT p FROM PostImage p WHERE p.title = :title")})
public class PostImage implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Basic(optional = false)
#NotNull
#Column(name = "post_image_id")
private Integer postImageId;
#Basic(optional = false)
#NotNull
#Size(min = 1, max = 500)
#Column(name = "path")
private String path;
#Basic(optional = false)
#NotNull
#Size(min = 1, max = 500)
#Column(name = "title")
private String title;
#JoinColumn(name = "post_id", referencedColumnName = "post_id")
#ManyToOne(optional = false)
private Post postId;
public PostImage() {
}
public PostImage(Integer postImageId) {
this.postImageId = postImageId;
}
public PostImage(Integer postImageId, String path, String title) {
this.postImageId = postImageId;
this.path = path;
this.title = title;
}
public Integer getPostImageId() {
return postImageId;
}
public void setPostImageId(Integer postImageId) {
this.postImageId = postImageId;
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public Post getPostId() {
return postId;
}
public void setPostId(Post postId) {
this.postId = postId;
}
#Override
public int hashCode() {
int hash = 0;
hash += (postImageId != null ? postImageId.hashCode() : 0);
return hash;
}
#Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof PostImage)) {
return false;
}
PostImage other = (PostImage) object;
if ((this.postImageId == null && other.postImageId != null) || (this.postImageId != null && !this.postImageId.equals(other.postImageId))) {
return false;
}
return true;
}
#Override
public String toString() {
return "entity.PostImage[ postImageId=" + postImageId + " ]";
}
}
i want to get collection of images for particular post like
Collection objPostImage = objPost.getPostImageCollection()
but manytoone relationship do not provide this functionality to me how can i convert it to one to many or how can i get Image Collection for a post.?
I am new to java so any help and suggestion will be appreciated
thanx in advance...

You can add a java.util.Set of PostImages in your Post object, and use the Hibernate mapping to provide the relationship. This site has a great example of setting up One to Many relationships.
So, for example, you would want to add something like the following to your Post class:
private Set<PostImage> postImages = new HashSet<PostImage>();
#OneToMany(fetch = FetchType.LAZY, mappedBy = "post")
public Set<PostImage> getPostImages() {
return this.postImages;
}
public void setPostImages(Set<PostImage> postImages) {
this.postImages= postImages;
}
Then, in your PostImage class, add a reference to a Post object:
private Post post;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "POST_ID", nullable = false)
public Stock getPost() {
return this.post;
}
public void setPost(Post post) {
this.post= post;
}
After adding that, you will be able to call the getPostImages() method on your Post object.

Try this:
#Entity
#Table(name = "post")
public class Post
{
//....
#OneToMany(mappedBy = "post")
private Set<PostImage> images;
//....
}
#Entity
#Table(name = "post_image")
public class PostImage
{
//....
#JoinColumn(name = "post_id", referencedColumnName = "id")
#ManyToOne(optional = false)
private Post post;
//....
}
The reason why Seth's answer didn't work is because EclipseLink uses fields to access persistence data. (Hibernate uses properties IIRC.) You can specify per class how a JPA provider should access this data.
Using fields:
#Entity
#Access(AccessType.FIELD)
public class SomeEntity
{
#Id
private Long id;
//....
}
Using properties:
#Entity
#Access(AccessType.PROPERTY)
public class SomeEntity
{
private Long id;
//....
#Id
public Long getId()
{
return id;
}
}
However when using #Access(AccessType.PROPERTY) fields are also used (at least in EclipseLink) so something like this is possible:
#Entity
#Access(AccessType.PROPERTY)
public class SomeEntity
{
private Long id;
#Column(name = "text")
private String someText;
//....
#Id
public Long getId()
{
return id;
}
}