CODEWITHSUNDEEP
javamysqlspringhibernatejpa
max5336
max5336

Reputation: 49

JPA ManyToMany - Always create a new value in the table even if the value exists

I'm going trough some trouble. I am coding the back-end of a website in spring and I am using a Rest API. I created two classes that are the relation "ManyToMany". The first class is "StateOfArt" and the second is "Tag". When I start the server , I post 2 StateOfArt in Json (I'm using Insomnia) and it's working pretty well. I mean The two StateOfArt are in my DB. The problem is that Tags are duplicated even if the two StateOfArt have the same tags.

Here is an example: I'm posting two StateOfArt in Json and this is ma DB:

My table StateOfArt

My table Tag

My Join table

I would like to have this in my join table:

1 1

1 2

2 1

2 2

And I would like to not have the redundancy in the table tag.

Is it possible to help me ?

Here the code of my two classes:

@Entity(name = "StateOfArt")
public class StateOfArt {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Integer id;
    private String author;
    private String title;
    private String date;
    private ArrayList<String> co_author;
    private String theabstract;

    //@ManyToMany(fetch = FetchType.LAZY ,cascade = {CascadeType.ALL})
    @ManyToMany(fetch = FetchType.LAZY, cascade = {
            CascadeType.ALL
    })
    @JoinTable(name = "state_of_art_tag",
            joinColumns = @JoinColumn(name = "stateofart_id"),//, referencedColumnName = "id"),
            inverseJoinColumns = @JoinColumn(name = "tag_id"))//, referencedColumnName = "id"))
    //@JsonIgnore
    private Set<Tag> tags = new HashSet<>();

    public StateOfArt(){}

    public StateOfArt(Integer id, String author, String title, String date,ArrayList<String> co_author,String theabstract, HashSet<Tag> tags){
        super();
        this.id = id;
        this.title = title;
        this.author =author;
        this.date =date;
        this.co_author = co_author;
        this.theabstract = theabstract;
        //this.articles = articles;
        this.tags = tags;

    }



    //Getters and Setters are here
}

@Entity(name = "Tag")
@Table(name = "tag_for_stateofart")
public class Tag {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    Integer id;

    @Column(length = 50)
    private String name;


    @ManyToMany(mappedBy = "tags")
    private Set<StateOfArt> stateofarts = new HashSet<>();

    public Tag() {}

    public Tag(String name) {
        this.name = name;
    }

    public String getTag() {
        return this.name;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Tag tag = (Tag) o;
        return Objects.equals(name, tag.name);
    }
}

Thank you for your help.

Upvotes: 0

Views: 342

Answers (2)

Peter Š&#225;ly
Peter Š&#225;ly

Reputation: 2933

Probably you are creating the same tag again. Check if tag with that name exists in DB, if yes, load it from Tag table.

Upvotes: 1

Naya
Naya

Reputation: 870

It must be a problem with tags table in your your database. When you create the table you should specify column name in tags table to have unique values.

Upvotes: 0

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