Develop Reference

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.

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;

Unable to delete the data in child entity in One-To-Many relationship

I have 2 entities: Product and ProductLine. One Product can have many ProductLines. I am unable to delete the Product associated with a particular ProductLine.
Product.java
#Entity
#Table(name = "PRODUCT")
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
ProductLine.java
#Entity
#Table(name = "PRODUCTLINE")
#JsonSerialize
public class ProductLine {
#JsonIgnore
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Product> getProducts() {
return products;
}
public void setProducts(List<Product> products) {
this.products = products;
}
private String name;
#JsonIgnore
#OneToMany(cascade = CascadeType.ALL)
#JoinTable(name = "PRODUCTLINE_PRODUCT", joinColumns = #JoinColumn(name = "PRODUCTLINE_ID"), inverseJoinColumns = #JoinColumn(name = "PRODUCT_ID"))
private List<Product> products;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
You can find the entire code in - https://github.com/iftekharkhan09/ProductRepository.git
The Code is in Spring boot.
Please execute the below in postman:
Add product Line (POST)
http://localhost:8080/data/addProductLine?productLine=apple
Add Product to Product Line(POST)
http://localhost:8080/data/addProduct
body:
[
{
"productLine": "apple",
"productName":"mac"
}
,
{
"productLine": "apple",
"productName":"iphone"
}
]
TO delete the Product(POST) :-
http://localhost:8080/data/deleteProduct?productLineName=apple&productName=mac
In the console I can not see the delete query being fired.
Any help will be highly appreciated.

How to create a many to many relationship with extra columns in jhipster?

The jhipster doesn't support create many to many relationships with extra fields.
What is the best way to create many to many association with extra columns in jhispter? Should i create a two one-to-many relationship with extra fields?

Using JHipster Domain Language (JDL), a #ManytoMany holding extra properties (columns) can be easily achieved using an association entity and two ManyToOne relationships. See below:
entity Foo{
...
}
entity Bar{
...
}
entity FooBarAssociation{
extraProperty1 String
extraProperty2 String
...
}
relationship ManyToOne {
FooBarAssociation{foo} to Foo{bars}
FooBarAssociation{bar} to Bar{foos}
}

You will have to do it manually.
this post describes how: https://hellokoding.com/jpa-many-to-many-extra-columns-relationship-mapping-example-with-spring-boot-maven-and-mysql/
In general, as #Antares42 said, you should create an entity for the Many-To-Many table like so:
first entity:
#Entity
public class Book{
private int id;
private String name;
private Set<BookPublisher> bookPublishers;
public Book() {
}
public Book(String name) {
this.name = name;
bookPublishers = new HashSet<>();
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
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;
}
#OneToMany(mappedBy = "book", cascade = CascadeType.ALL, orphanRemoval = true)
public Set<BookPublisher> getBookPublishers() {
return bookPublishers;
}
public void setBookPublishers(Set<BookPublisher> bookPublishers) {
this.bookPublishers = bookPublishers;
}
}
secound entity:
#Entity
public class Publisher {
private int id;
private String name;
private Set<BookPublisher> bookPublishers;
public Publisher(){
}
public Publisher(String name){
this.name = name;
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
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;
}
#OneToMany(mappedBy = "publisher")
public Set<BookPublisher> getBookPublishers() {
return bookPublishers;
}
public void setBookPublishers(Set<BookPublisher> bookPublishers) {
this.bookPublishers = bookPublishers;
}
}
Join table entity:
#Entity
#Table(name = "book_publisher")
public class BookPublisher implements Serializable{
private Book book;
private Publisher publisher;
private Date publishedDate;
#Id
#ManyToOne
#JoinColumn(name = "book_id")
public Book getBook() {
return book;
}
public void setBook(Book book) {
this.book = book;
}
#Id
#ManyToOne
#JoinColumn(name = "publisher_id")
public Publisher getPublisher() {
return publisher;
}
public void setPublisher(Publisher publisher) {
this.publisher = publisher;
}
#Column(name = "published_date")
public Date getPublishedDate() {
return publishedDate;
}
public void setPublishedDate(Date publishedDate) {
this.publishedDate = publishedDate;
}
}
This entity describes the relationship between Book and Publisher and the extra field is published_date

Let's say you have entities like Movie, Rater and needs a join table Ratings. You can write a JDL script like the following:
entity Movie { title String}
entity Rater { name String}
entity Rating { value Integer} //the extra field
relationship ManyToMany {
Rating{rater(name)} to Rater,
Rating{movie(title)} to Movie
}
save it in file.jdl in the project folder, open cmd type
jhipster import-jdl file.jdl
and you have everything

Hibernate HQL Join Query DOT node with no left-hand-side

I have two model classes
Application.java
#Entity
#Table(name = "Application", catalog = "mysqldb")
#XmlRootElement
public class Application extends BaseObject implements Serializable {
private Long appId;
private Long userId;
private String name;
private String desc;
#Id
#Column(name = "AppId")
#GeneratedValue(strategy = GenerationType.AUTO)
public Long getAppId() {
return this.appId;
}
public void setAppId(Long appId) {
this.appId = appId;
}
#Column(name = "userId", nullable = false)
public Long getUserId() {
return this.userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
#Column(name = "name", length = 128, nullable = false)
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
#Column(name = "Desc")
public String getDesc() {
return this.desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
}
User.java
#Entity
#Table(name="User",catalog="mysqldb")
#XmlRootElement
public class Client extends BaseObject implements Serializable {
private Long userId;
private String name;
#Id
#Column(name="userId")
#GeneratedValue(strategy=GenerationType.AUTO)
public Long getUserId() {
return this.userId;
}
public void setClientId(Long clientId) {
this.clientId = clientId;
}
#Column(name="Name", length=128)
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
I have not mentioned any relationship between both.
I am trying to get a list of applications with user ID and also to get the name of user.
In my ApplicationDaoImpl java class I have the following method.
#Override
public List<ApplicationObj> getAllByUser(
Long userId) {
String queryString = "select application.appId as appId, application.userId as userId, user.name as name, application.name as name"
+ " from com.mydb.model.Application application join com.mydb.model.User user"
+ " with application.userId = user.userId"
+ " where application.userId=?";
Session session = getSession();
Query query = session.createQuery(queryString);
query.setParameter(0, userId);
List list = query.list();
return new ArrayList<ApplicationObj>();
}
I am trying to get the result and set in a new object. (Setting to new object is not done yet.)
When I try executing this, I get the following exception
java.lang.IllegalStateException: DOT node with no left-hand-side!
at org.hibernate.hql.internal.ast.tree.DotNode.getLhs(DotNode.java:616)
at org.hibernate.hql.internal.ast.tree.DotNode.getDataType(DotNode.java:595)
at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:380)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3516)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3302)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3180)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:706)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:562)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:299)
at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:247)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:248)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:183)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:105)
at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:168)
at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:221)
at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:199)
at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1735)
at com.mypgm.dao.hibernate.ApplicationDaoImpl.getAllByUser(ApplicationDaoImpl.java:74)
How to solve this? Or how to do join query without mapping any relationships