How to solve unexpected token exception in Spring mvc and hibernate?

Question

My application is a Spring MVC and hibernate based one. In the below hql statement I'm mapping the resultset to the custom class named 'Result'. Here is my HQL statement,

        String hql=
                "select new com.gavs.beans.Result(distinct(d.dept_name) as dept_name,distinct(c.college_name) as college_name)"+
                " from com.gavs.beans.College c" + 
                " join com.gavs.beans.Department d on d.institutes.college_id = c.college_id";

        org.hibernate.query.Query q = session.createQuery(hql);

        List<Result> r1= q.list();


       return r1;

I get these following exceptions in the hql statement

Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:34: unexpected token: distinct
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:34: unexpected token: distinct
line 1:34: unexpected token: distinct
.
.
.
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:43: unexpected token: d
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:43: unexpected token: d
line 1:43: unexpected token: d
.
.
.
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:56: unexpected token: as
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:56: unexpected token: as
line 1:56: unexpected token: as
.
.
.
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:92: expecting EOF, found ')'
Jun 09, 2020 3:33:24 PM org.hibernate.hql.internal.ast.ErrorTracker reportError
ERROR: line 1:92: expecting EOF, found ')'
line 1:92: expecting EOF, found ')'
.
.
.
Jun 09, 2020 3:33:24 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [studentDetails] in context with path [/HibernateWithQuery] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: distinct near line 1, column 34 [select new com.gavs.beans.Result(distinct(d.dept_name) as dept_name,distinct(c.college_name) as college_name) from com.gavs.beans.College c join com.gavs.beans.Department d on d.institutes.college_id = c.college_id]] with root cause
org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: distinct near line 1, column 34 [select new com.gavs.beans.Result(distinct(d.dept_name) as dept_name,distinct(c.college_name) as college_name) from com.gavs.beans.College c join com.gavs.beans.Department d on d.institutes.college_id = c.college_id]

Here is the Student Entity (Student.java)

package com.gavs.beans;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="STUDENT_TABLE")
public class Student{

    @Id
    @Column(name="Roll_No")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int roll_no;

    @Column(name="Name")
    private String name;

    @Column(name="Age")
    private int age;

    @Column(name="Address")
    private String address;

    @ManyToOne
    @JoinColumn(name="Dept_Id")
    private Department departments;



    public Student() {
        super();
    }

        public int getRoll_no() {
        return roll_no;
    }

    public void setRoll_no(int roll_no) {
        this.roll_no = roll_no;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }


    public Department getDepartments() {
        return departments;
    }

    public void setDepartments(Department departments) {
        this.departments = departments;
    }


}

This is the Department Entity(Department.java)

package com.gavs.beans;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="DEPARTMENT_TABLE")
public class Department {

    @Id
    @Column(name="Dept_Id")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private int dept_id;

    @Column(name="Dept_Name")
    private String dept_name;

    @Column(name="Dept_Code")
    private int dept_code;

    @ManyToOne
    @JoinColumn(name="College_Id")
    private College institutes;


    public int getDept_id() {
        return dept_id;
    }


    public Department() {
        super();
    }


    public void setDept_id(int dept_id) {
        this.dept_id = dept_id;
    }

    public String getDept_name() {
        return dept_name;
    }
    public void setDept_name(String dept_name) {
        this.dept_name = dept_name;
    }

    public int getDept_code() {
        return dept_code;
    }
    public void setDept_code(int dept_code) {
        this.dept_code = dept_code;
    }


     public College getColleges() {
        return institutes;
    }


    public void setColleges(College institutes) {
        this.institutes = institutes;
    }


}

This is the College Entity(College.java)

package com.gavs.beans;

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="COLLEGE_TABLE")
public class College {

@Id
@Column(name="College_Id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int college_id;

@Column(name="College_Name")
private String college_name;

@Column(name="College_Address")
private String college_address;

@OneToMany(mappedBy="institutes",cascade=CascadeType.ALL)
private List<Department> departments;

public College() {

}

public int getCollege_id() {
    return college_id;
}
public void setCollege_id(int college_id) {
    this.college_id = college_id;
}

public String getCollege_name() {
    return college_name;
}
public void setCollege_name(String college_name) {
    this.college_name = college_name;
}

public String getCollege_address() {
    return college_address;
}
public void setCollege_address(String college_address) {
    this.college_address = college_address;
}
public List<Department> getDepartments() {
    return departments;
}

public void setDepartments(List<Department> departments) {
    this.departments = departments;
}

}

Answer 1

Try to use Interface projection with JPA repository

public interface Result{
    String getDepartmentName();
    String getCollegeName();
}

And in your Jpa repository:

@Query("select distinct d.dept_name as departmentName, d.institutes.college_name as collegeName from Department d")
List<Result> findDistinctDepartmentAndCollegeName();