fetch one to many side with jpql - jpa

Question

so I have done two entities with one to many relationship,
I have one category whohas many visitors,
and this is my code:
this is the Category entity :
#Entity
public class Category implements Serializable {
private Integer id;
private String name;
private List<Visitor> visitors = new ArrayList<Visitor>();
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
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;
}
#OneToMany(cascade=CascadeType.REMOVE, fetch = FetchType.LAZY, mappedBy = "category", orphanRemoval = true)
public List<Visitor> getVisitors() {
return visitors;
}
public void setVisitors(List<Visitor> visitors) {
this.visitors = visitors;
}
}
and here is the Visitor Entity :
#Entity
public class Visitor extends User {
private String passport;
private String citizenship;
private String gender;
private Company company;
private Category category;
public String getPassport() {
return passport;
}
public void setPassport(String passport) {
this.passport = passport;
}
public String getCitizenship() {
return citizenship;
}
public void setCitizenship(String citizenship) {
this.citizenship = citizenship;
}
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
public Company getCompany() {
return company;
}
public void setCompany(Company company) {
this.company = company;
}
and here is the service method who list all the visitors and works fine :
public List<Visitor> findAllVisitors() {
return em.createQuery(
"SELECT v from Visitor v left join fetch v.category",
Visitor.class).getResultList();
}
with this method I can list all the visitors each with his category object associated,
now the problem is in the other side of the relationship ,
here is the method who list the categories each with their visitors list :
public List<Category> findAllCategories() {
return em.createQuery("select c from Category c",
Category.class).getResultList();
}
I want to get the list of all the categories but when I call this method in a REST call , I get this result :
I want just to get a simple list of categories (id and name).
what is wrong in my code please help me i am confused.
UPDATE:
this is how I get JSON from persistence context with RESTful method :
#Inject
private CategoryServiceLocal categoryServiceLocal;
#GET
#Produces(MediaType.APPLICATION_JSON)
public List<Category> dofindAllCategories() {
return categoryServiceLocal.findAllCategories();
}

Answer 1

You have a lazy association from Category to visitors. To load all visitors you need to use left join fetch too.
select c from Category c left join fetch c.visitors
Please, use additional annotations to control how to JSON generated
Infinite Recursion with Jackson JSON and Hibernate JPA issue