JPA Criteria GROUP BY Clause

The GROUP BY clause is used to collect data from one or more tables and arrange them in a group. In Criteria API, the groupBy() method of AbstractQuery interface is used to filter the records and group them.

Criteria GROUP BY Example

Here, we will perform GROUP BY operations on student table. Let us assume the table contains the following records: -

Now, follow the below steps to perform operations: -

Step 1. Create an entity class names as StudentEntity.java under com.javahubpoint.jpa package. This class contains three attributes s_id, s_name and s_age with all the required annotations.

StudentEntity.java

package com.javahubpoint.jpa;  
    import javax.persistence.*;  
  
    @Entity  
    @Table(name="student")  
    public class StudentEntity {  
  
        @Id  
        private int s_id;  
        private String s_name;  
        private int s_age;  
          
        public StudentEntity(int s_id, String s_name, int s_age) {  
            super();  
            this.s_id = s_id;  
            this.s_name = s_name;  
            this.s_age = s_age;  
        }  
  
        public StudentEntity() {  
            super();  
        }  
  
        public int getS_id() {  
            return s_id;  
        }  
  
        public void setS_id(int s_id) {  
            this.s_id = s_id;  
        }  
  
        public String getS_name() {  
            return s_name;  
        }  
  
        public void setS_name(String s_name) {  
            this.s_name = s_name;  
        }  
  
        public int getS_age() {  
            return s_age;  
        }  
  
        public void setS_age(int s_age) {  
            this.s_age = s_age;  
        }  
          
    }  

Step 2.  Now, map the entity class and other databases configuration in Persistence.xml file.

Persistence.xml

<persistence>  
<persistence-unit name="Student_details">  
     
      <class>com.javahubpoint.jpa.StudentEntity</class>  
  
      <properties>  
         <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>  
         <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/studentdata"/>  
         <property name="javax.persistence.jdbc.user" value="root"/>  
         <property name="javax.persistence.jdbc.password" value=""/>  
         <property name="eclipselink.logging.level" value="SEVERE"/>  
         <property name="eclipselink.ddl-generation" value="create-or-extend-tables"/>  
      </properties>  
        
   </persistence-unit>  
  
</persistence>  

Step 3.  Once, we created the basic entity class and mapped the configuration into persistence.xml file, we can perform the different types of GROUP BY operation. Here, we are grouping the number of students on the basis of age.

StudentGroup.java

package com.javahubpoint.jpa.jpql;  
import com.javahubpoint.jpa.StudentEntity;  
import javax.persistence.*;  
import javax.persistence.criteria.*; 
import java.util.*;

public class StudentGroup {  
 
    public static void main( String args[]) {
           
         EntityManagerFactory emf = Persistence.createEntityManagerFactory( "Student_details" );  
          EntityManager em = emf.createEntityManager();  
          em.getTransaction().begin( );  
            
CriteriaBuilder cb = em.getCriteriaBuilder();  
CriteriaQuery<Object[]> cq = cb.createQuery(Object[].class);  
Root<StudentEntity> stud = cq.from(StudentEntity.class);  
cq.multiselect(stud.get("s_age"),cb.count(stud)).groupBy(stud.get("s_age"));  
       
System.out.print("s_age");  
System.out.println("\t Count");  
List<Object[]> list = em.createQuery(cq).getResultList();  
for(Object[] object : list){  
    System.out.println(object[0] + "     " + object[1]);  
  
}  
  
em.getTransaction().commit();  
          em.close();  
          emf.close();    
     }  
}

Output: