What is root path in QueryDSL? Can you explain with an example? - jpa

Question

I have the following two entity classes: Country and Type
#Entity
#Table(name = "countries")
public class Country {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id ;
#Column(name = "iso_code")
private String isoCode;
public Country() {
}
public Country(String isoCode) {
this.isoCode = isoCode;
}
public Country(int id, String isoCode) {
this.id = id;
this.isoCode = isoCode;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getIsoCode() {
return isoCode;
}
public void setIsoCode(String isoCode) {
this.isoCode = isoCode;
}
#Override
public String toString() {
return "Country{" +
"id=" + id +
", isoCode='" + isoCode + '\'' +
'}';
}
}
#Entity
#Table(name = "types")
public class Type {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
#Column(name = "type")
private String type;
#ManyToOne
#JoinColumn(name = "country_id")
private Country country;
#ManyToOne
#JoinColumn(name = "group_id")
private Group group;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public Group getGroup() {
return group;
}
public void setGroup(int priority) {
this.group = group;
}
}
I am trying to retrieve groups using the following in the repository class:
QType qType = QType.type1;
QCountry qCountry = QCountry.country;
QGroup qGroup = QGroup.group;
QGroup qGroup1 = qType.group;
JPAQuery queryGroup = new JPAQuery(em);
QueryBase queryBaseGroups = queryGroup.from(qGroup).innerJoin(qGroup1, qGroup).innerJoin(qType.country, qCountry);
However, I get the error -
java.lang.IllegalArgumentException: Undeclared path 'type1'. Add this path as a source to the query to be able to reference it.
New to JPA. What am I doing wrong here?

Answer 1

So this was solved by adding qType to the from function in the query.
QueryBase queryBaseGroups = queryGroup.from(qGroup, qType).innerJoin(qGroup1, qGroup).innerJoin(qType.country, qCountry);