Hibernate Create Criteria Projections:

Projections in hibernate helps to retrieve data based in SQL aggregate functions.

avg(String propertyName)

     A property average value

 

count(String propertyName)

     A property value count

 

countDistinct(String propertyName)

     A distinct property value count

 

distinct(Projection proj)

     Create a distinct projection from a projection

 

groupProperty(String propertyName)

     A grouping property value

 

max(String propertyName)

     A property maximum value

 

min(String propertyName)

     A property minimum value

 

rowCount()

    The query row count, ie.

 

sum(String propertyName)

    A property value sum

Example:

public void getProjectionResult() {
    try {
      Session s = getSession();
      Criteria c = s.createCriteria(Employee.class);
      c.setProjection(Projections.avg("salary"));
      List avg = c.list();
      System.out.println("Average Salary :" + avg);
      c.setProjection(Projections.min("age"));
      List min = c.list();
      System.out.println("Minimum Age :" + min);
      c.setProjection(Projections.max("experience"));
      List max = c.list();
      System.out.println("Maximum Experience :" + max);
      c.setProjection(Projections.count("name"));
      List count = c.list();
      System.out.println("Employee Count :" + count);
      c.setProjection(Projections.sum("salary"));
      List sum = c.list();
      System.out.println("Sum Of Salary :" + sum);
      c.setProjection(Projections.countDistinct("name"));
      List distinct = c.list();
      System.out.println("Distinct values in Name:" + distinct);
    } catch (Exception e) {
      System.out.println(e.getMessage());
    } 

POJO:

package com.candidjava.hibernate;
import java.io.Serializable;
public class Employee implements Serializable {
  private long Id;
  private String name;
  private int age;
  private String gender;
  private int salary;
  private int experience;
  private String address;
  private long mobile;
  public long getId() {
    return Id;
  }
  public void setId(long id) {
    Id = id;
  }
  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 getGender() {
    return gender;
  }
  public void setGender(String gender) {
    this.gender = gender;
  }
  public int getSalary() {
    return salary;
  }
  public void setSalary(int salary) {
    this.salary = salary;
  }
  public int getExperience() {
    return experience;
  }
  public void setExperience(int experience) {
    this.experience = experience;
  }
  public String getAddress() {
    return address;
  }
  public void setAddress(String address) {
    this.address = address;
  }
  public long getMobile() {
    return mobile;
  }
  public void setMobile(long mobile) {
    this.mobile = mobile;
  }
}

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