Custom result objects with Criteria4JPA

CountryAndQuantity.java

public static class CountryAndQuantity {
  
  private final String country;
  private final Long quantity;

  public CountryAndQuantity(String country, Long quantity) {
    this.country = country;
    this.quantity = quantity;
  }

  public String getCountry() {
    return country;
  }

  public Long getQuantity() {
    return quantity;
  }
  
}

PersonDao.java

// Create new criteria
Criteria criteria = CriteriaUtils.createCriteria( entityManager, Person.class );

// Add constructor projection
criteria.setProjection( Projections.constructor( CountryAndQuantity.class )
    .add( Projections.relativeGroupPath("country") )
    .add( Projections.count("id") )
);

// Execute the query
List<CountryAndQuantity> result = criteria.getResultList();

// Display result
for( CountryAndQuantity row : result ) {
  log.info( "There are " + row.getQuantity() + " people from " + row.getCountry() );
}

Result

There are 8 people from US
There are 3 people from Germany
There are 2 people from France