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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.

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.

JPA get join table data condition [duplicate]

When I send a GET request in POSTMAN to get all my child entity (Town) the parent entity (Province) is not shown in the JSON response.
This is my controller.
#RequestMapping(value ="api/v1/town",method = RequestMethod.GET)
public ResponseEntity<List<Town>> getAllTowns() {
List<Town> towns = townService.getAllTowns();
if(towns.isEmpty()) {
return new ResponseEntity<List<Town>>(HttpStatus.NO_CONTENT);
}
return new ResponseEntity<List<Town>>(towns, HttpStatus.OK);
}
And these are my entities.
Parent Class
#Entity
#Table(name = "PROVINCE")
public class Province {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "PROVINCE_ID")
private long id;
private String name;
#OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "province", targetEntity = Town.class)
#JsonManagedReference("Province-Town")
private List<Town> towns;
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 List<Town> getTowns() {
return towns;
}
public void setTowns(List<Town> towns) {
this.towns = towns;
}
}
Child Class
#Entity
#Table(name = "TOWN")
public class Town {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "TOWN_ID")
private long id;
private String name;
#ManyToOne(cascade = CascadeType.MERGE)
#JoinColumn(name = "PROVINCE_ID")
#JsonBackReference("Province-Town")
private Province province;
private long kilometer;
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 Province getProvince() {
return province;
}
public void setProvince(Province province) {
this.province = province;
}
public long getKilometer() {
return kilometer;
}
public void setKilometer(long kilometer) {
this.kilometer = kilometer;
}
}
The response that I'm getting is like this
{
"id" : 1,
"name" : "Some Town",
"kilometer" : 350
}
What I'm expecting is
{
"id" : 1,
"name" : "Some Town",
"province" : {
//Province data.....
}
"kilometer" : 350
}
I was able to show something like this, but the Objects that I used are not Spring-data-jpa entities, just simple POJOs.
Is there any problem with my Entities? Or is there anything else?

Swap #JsonBackReference and #JsonManagedReference. Basically:
#JsonManagedReference
private Province province;
#JsonBackReference
private List<Town> towns;

ResultSet error executing #Query in JPA Reposity, using nativeQuery = true

I am working on a web application using:
Spring Boot
PostgreSQL
JPA and Hibernate.
I have a table called role and another page. Among them there is a many-to-many table with ID's. What I'm trying to get is the list of pages that correspond to a role, so I'm trying to retrieve the list of pages from the id of the role and executing a query to bring the list. The problem is that I have an error in the ResultSet because it tells me that it does not find a column with the name page_id.
Example:
I have executed the query separately and this brings me results correctly.
select p.url from role_page rp, page p where rp.role_id = 6 and rp.page_id = p.page_id;
Output:
Output of the query
Then I made a call to the function to get the list and check it to make sure I get results.
public void rolesAndPages(){
List<Page> pages = pageRepository.findPagePerRole(6);
for (Page page: pages
) {
System.out.println(page.getUrl());
}
}
And throws the error described above:
org.postgresql.util.PSQLException: The column name page_id was not found in this ResultSet.
My Repository:
#Repository("pageRepository")
public interface PageRepository extends JpaRepository<Page, Long> {
#Query(value = "select p.url from role_page rp, page p where rp.role_id = ?1 and rp.page_id = p.page_id", nativeQuery = true)
List<Page> findPagePerRole(Integer id);
}
Role.java
#Entity
#Table(name = "app_role")
public class Role {
#Id
#SequenceGenerator(name="pk_sequence",sequenceName="messagesounds_id_seq", allocationSize=1)
#GeneratedValue(strategy=GenerationType.SEQUENCE,generator="pk_sequence")
#Column(name="role_id")
private int id;
#Column(name="authority")
#NotEmpty(message = "*Please provide a name")
private String authority;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "role_page", joinColumns = #JoinColumn(name = "role_id"), inverseJoinColumns = #JoinColumn(name = "page_id"))
private Set<Page> pages;
public void setPages(Set<Page> pages) {
this.pages = pages;
}
public Set<Page> getPages() {
return pages;
}
public Role() {}
public Role(String authority) {
this.authority = authority;
}
public Role(String authority, Set<Page> pages){
this.authority = authority;
this.pages = pages;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAuthority() {
return authority;
}
public void setAuthority(String authority) {
this.authority = authority;
}
}
Page.java
#Entity
#Table(name = "page")
public class Page {
#Id
#SequenceGenerator(name = "pk_sequence", sequenceName = "messagesounds_id_seq", allocationSize = 1)
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "pk_sequence")
#Column(name = "page_id")
private int id;
#Column(name = "name_page")
#NotEmpty(message = "*Please provide a name")
private String name;
#Column(name = "url")
#NotEmpty(message = "*Please provide an url")
private String url;
#Column(name = "description")
#NotEmpty(message = "*Please provide a description")
private String description;
#ManyToMany(mappedBy = "pages")
private Set<Role> roles;
public Page() {
}
public Page(String name_page) {
this.name = name_page;
}
public Page(String name_page, Set<Role> roles) {
this.name = name_page;
this.roles = roles;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Set<Role> getRoles() {
return roles;
}
public void setRoles(Set<Role> roles) {
this.roles = roles;
}
}

The error is quite explicite, you need to select page_id column to make it work, not only p.url.
Try this to retrieve every column of Page :
#Query(value = "select p.* from role_page rp, page p where rp.role_id = ?1 and rp.page_id = p.page_id", nativeQuery = true)
Or, this to retrieve every columns of tables Page and Role_Page :
#Query(value = "from role_page rp, page p where rp.role_id = ?1 and rp.page_id = p.page_id", nativeQuery = true)
The both queries should work.

Did you tried :
#Query(value = "select p.url from role_page rp, page p where rp.id = ?1 and rp.id = p.id")

How to create inner HQL

I'm trying to query data from a sub query using HQL. I have 2 classes:
Supplier.java:
#Entity
#Table(name = "Suppliers")
public class Supplier implements Serializable {
#Id
String id;
String name;
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#JoinTable(name = "Suppliers_Categories", joinColumns = { #JoinColumn(name = "SupplierId") }, inverseJoinColumns = { #JoinColumn(name = "CategoryId") })
Set<Category> categories = new HashSet<Category>();
#OneToMany(mappedBy = "supplier")
Collection<Product> products;
public Set<Category> getCategories() {
return this.categories;
}
public void setCategories(Set<Category> categories) {
this.categories = categories;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Collection<Product> getProducts() {
return products;
}
public void setProducts(Collection<Product> products) {
this.products = products;
}
}
Category.java:
#Entity
#Table(name = "Categories")
public class Category implements Serializable {
#Id
#GeneratedValue
Integer id;
String name;
String namevn;
#ManyToMany(mappedBy = "categories")
Set<Supplier> suppliers = new HashSet<Supplier>(0);
#OneToMany(mappedBy = "category")
Collection<Product> products;
#OneToOne
#JoinColumn(name = "ProductFeature")
Product featureProduct;
public Set<Supplier> getSuppliers() {
return this.suppliers;
}
public Product getFeatureProduct() {
return featureProduct;
}
public void setFeatureProduct(Product featureProduct) {
this.featureProduct = featureProduct;
}
public String getNamevn() {
return namevn;
}
public void setNamevn(String namevn) {
this.namevn = namevn;
}
public void setSuppliers(Set<Supplier> suppliers) {
this.suppliers = suppliers;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Collection<Product> getProducts() {
return products;
}
public void setProducts(Collection<Product> products) {
this.products = products;
}
}
What i need is select "supplier.id" in Category which has id = 1. My query is:
SELECT id FROM Supplier as s where s in (SELECT suppliers FROM Category as c WHERE c.id = 1)
But it has some errors :
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not execute query
at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:90)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
at org.hibernate.loader.Loader.doList(Loader.java:2231)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2125)
at org.hibernate.loader.Loader.list(Loader.java:2120)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:361)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1148)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
at eshop.util.XHibernate.list(XHibernate.java:85)
at eshop.util.XHibernate.main(XHibernate.java:91)
Caused by: com.microsoft.sqlserver.jdbc.SQLServerException: Incorrect syntax near '-'.
at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:196)
at com.microsoft.sqlserver.jdbc.SQLServerStatement.getNextResult(SQLServerStatement.java:1458)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:388)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement$PrepStmtExecCmd.doExecute(SQLServerPreparedStatement.java:338)
at com.microsoft.sqlserver.jdbc.TDSCommand.execute(IOBuffer.java:4016)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.executeCommand(SQLServerConnection.java:1414)
at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeCommand(SQLServerStatement.java:176)
at com.microsoft.sqlserver.jdbc.SQLServerStatement.executeStatement(SQLServerStatement.java:151)
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.executeQuery(SQLServerPreparedStatement.java:281)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1808)
at org.hibernate.loader.Loader.doQuery(Loader.java:697)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259)
at org.hibernate.loader.Loader.doList(Loader.java:2228)
... 9 more
Is there any way to query as my idea using 1 hql ? Any help would be great.

You need to learn about joins. All you need is
select s.id from Supplier s
join s.categories c
where c.id = :categoryId