How to expose many to many relationship in spring boot

Question

I am facing a issue.. I have a many to many relationship with jpa in spring boot, but I need to expose the following product has many tags and tag has many product

if query product/1

{product:{name:"product 1"}, tags:[ tag1:{name:"tag 1"}, tag2:{name:"tag2"} ] }

if query tag/1

{tag:1, products:[ product1:[{name:"product 1"}, tag2:{product:"tag2"} ] }

what is the way to expose this with rest with spring boot? a example, url or and idea it would be useful.

not sure what you wanted.. are you looking for a way to map these to JPA entities? — Ish, Oct 06 '17 at 04:48
ah sorry I already have the mapping working , but maybe u know when you try to expose it as rest (converted to json) there is a infinite recursion exception , because the both sides relationship.. what i am looking is a new point of view to expose it as rest like my example, maybe I am not facing well the problem and there is a best way — Juan Pablo, Oct 06 '17 at 04:58
Try this link: http://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion — Ish, Oct 06 '17 at 05:11
So if you have the JPA mapping working then the problem is nothing to do with JPA, and everything to do with JSON, so remove the `JPA` tag from the question — , Oct 06 '17 at 07:22

score 2 · Accepted Answer · answered Oct 06 '17 at 05:10

You need to use a combination of @JsonManagedReference and @JsonBackReference annotations to stop an infinite recursion from occurring when you try and serialise your JPA beans.

Have a look at some of these questions for further info:

score 1 · Answer 2 · answered Feb 11 '20 at 20:27

There are multiple alternatives to stop infinite recursion:

@JsonManagedReference and @JsonBackReference:

@Entity
public class Product {
    @ManyToMany
    @JsonManagedReference
    private List<Tag> tags = new ArrayList<Tag>();
}

@Entity
public class Tag implements {
    @ManyToMany(mappedBy = "tags")
    @JsonBackReference
    private List<Product> products = new ArrayList<Product>();
}

@JsonIdentityInfo:

@Entity
public class Product {
    @ManyToMany
    private List<Tag> tags = new ArrayList<Tag>();
}

@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@Entity
public class Tag implements {
    @ManyToMany(mappedBy = "tags")
    private List<Product> products = new ArrayList<Product>();
}

@JsonIgnoreProperties:

@Entity
public class Product {
    @ManyToMany
    @JsonIgnoreProperties("products")
    private List<Tag> tags = new ArrayList<Tag>();
}

@Entity
public class Tag implements {
    @ManyToMany(mappedBy = "tags")
    @JsonIgnoreProperties("tags")
    private List<Product> products = new ArrayList<Product>();
}

How to expose many to many relationship in spring boot

2 Answers2