How convert this SQL query into JPA criteriaBuilder query? - sql

Question

I have the following Data Base diagram:
And I have the following quite simple SQL query:
SELECT Subject.id, Subject.name, subSelect.count
FROM
(SELECT Subject.id AS id, COUNT(*) AS count
FROM Question
JOIN Subject_Question ON Subject_Question.question_id = Question.id
JOIN Subject ON Subject.id = Subject_Question.subject_id
WHERE Subject.state = 0 AND Question.state = 0
GROUP BY Subject.id) AS subSelect
JOIN Subject ON Subject.id = subSelect.id
My task is to present this query Java application in term of criteriaBuilder from JPA.
This is my domain classes in Java application:
#Entity
#Table(name = "Question")
public class Question {
Long id;
String text;
ActiveUser activeUser;
Long dateCreation;
Long dateStateSetting;
EntityState state;
Set<Subject> subjects;
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#Column(name = "text", length = 5000, nullable = false)
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
#ManyToOne(cascade = CascadeType.REMOVE)
#JoinColumn(name = "activeUser", nullable = false)
public ActiveUser getActiveUser() {
return activeUser;
}
public void setActiveUser(ActiveUser activeUser) {
this.activeUser = activeUser;
}
#Column(name = "dateCreation")
public Long getDateCreation() {
return dateCreation;
}
public void setDateCreation(Long dateCreation) {
this.dateCreation = dateCreation;
}
#Column(name = "dateStateSetting")
public Long getDateStateSetting() {
return dateStateSetting;
}
public void setDateStateSetting(Long dateStateSetting) {
this.dateStateSetting = dateStateSetting;
}
#Enumerated(EnumType.ORDINAL)
#Column(name = "state", nullable = false)
public EntityState getState() {
return state;
}
public void setState(EntityState state) {
this.state = state;
}
#ManyToMany(mappedBy = "questions")
public Set<Subject> getSubjects() {
return subjects;
}
public void setSubjects(Set<Subject> subjects) {
this.subjects = subjects;
}
}
And
#Entity
#Table(name = "Subject")
public class Subject {
Long id;
String name;
EntityState state;
Long dateCreation;
Boolean ifGroup;
List<Question> questions;
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.IDENTITY)
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#Column(name = "name", nullable = false)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
#Enumerated(EnumType.ORDINAL)
#Column(name = "state", nullable = false)
public EntityState getState() {
return state;
}
public void setState(EntityState state) {
this.state = state;
}
#Column(name = "dateCreation")
public Long getDateCreation() {
return dateCreation;
}
public void setDateCreation(Long dateCreation) {
this.dateCreation = dateCreation;
}
#Column(name = "ifGroup", nullable = false)
public Boolean getIfGroup() {
return ifGroup;
}
public void setIfGroup(Boolean ifGroup) {
this.ifGroup = ifGroup;
}
#ManyToMany(cascade = CascadeType.REMOVE)
#JoinTable(
name = "Subject_Question",
joinColumns = #JoinColumn(name = "subject_id"),
inverseJoinColumns = #JoinColumn(name = "question_id")
)
public List<Question> getQuestions() {
return questions;
}
public void setQuestions(List<Question> questions) {
this.questions = questions;
}
}
I start with the following:
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Question> criteria = criteriaBuilder.createQuery(Question.class);
Root<Question> i = criteria.from(Question.class);
criteria.multiselect(
i.get("id"),
criteriaBuilder.count(i)).
But at this point I ran into a problem - I must to join with Subject_Question but I don't have class for it in Java application.
So is it possible to represent this SQL query in term of criteriaBuilder from JPA?