Modélisation de la clé primaire composite avec le champ de séquence

Question

J'ai une table où nous avons les colonnes orderId, locationId et sequenceNum en dehors des autres colonnes. Ces trois colonnes font partie de la contrainte de clé primaire. La colonne sequenceNum s'incrémente pour une combinaison orderId/locationId et redémarre à partir de 1 pour le prochain orderId/locationId. La génération sequenceNum doit donc être basée sur max (sequenceNum) +1 pour la combinaison orderId/locationId. Cela peut-il être modélisé avec JPA @Embeddable et @EmbeddedId? Comment réinitialiser la séquence à 1 pour la combinaison orderId/locationId?

Answer 1

Si vous utilisez le mode hibernation, vous pouvez utiliser cet exemple. Sinon, recherchez le générateur de séquence sur l'API que vous utilisez et utilisez la même logique.

Identifiable.java

package my.app.hibernate; 

import java.io.Serializable; 

public interface Identifiable<T extends Serializable> { 
    T getId(); 
} 

CompositeKeyEntity.java

package my.app.hibernate; 

import java.io.Serializable; 

public interface CompositeKeyEntity<T extends Serializable> extends Identifiable<T> { 
} 

SingleKeyEntity.java

package my.app.hibernate; 

import java.io.Serializable; 

public interface SingleKeyEntity<T extends Serializable> extends Identifiable<T> { 
} 

AssignedIdentityGenerator.java

package my.app.hibernate; 

import java.io.Serializable; 
import java.lang.reflect.Field; 
import java.util.Arrays; 
import java.util.List; 

import org.hibernate.Criteria; 
import org.hibernate.criterion.Projections; 
import org.hibernate.criterion.Restrictions; 
import org.hibernate.engine.spi.SessionImplementor; 
import org.hibernate.id.IdentityGenerator; 
import org.hibernate.internal.CriteriaImpl; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.security.util.FieldUtils; 

public class AssignedIdentityGenerator extends IdentityGenerator { 
    private static final String ID_FIELD_NAME = "id"; 
    private final Logger LOG = LoggerFactory.getLogger(this.getClass()); 
    private Field sequenceField; 
    private String entityClassName; 

    @Override 
    public Serializable generate(SessionImplementor session, Object obj) { 
     @SuppressWarnings("unchecked") 
     Identifiable<Serializable> identifiable = (Identifiable<Serializable>)obj; 

     entityClassName = obj.getClass().getName(); 
     Criteria criteria = new CriteriaImpl(entityClassName, session); 
     criteria.setReadOnly(true); 
     Object toSet = null; 

     if (identifiable instanceof CompositeKeyEntity) { 
      Serializable id = identifiable.getId(); 
      if (id != null) { 
       String embaddebleClassName = id.getClass().getName(); 
       buildCriteriaForEmbeddedId(id, embaddebleClassName, criteria); 
       toSet = id; 
      } 
     } else if (obj instanceof SingleKeyEntity) { 
      toSet = identifiable; 
      sequenceField = FieldUtils.getField(identifiable.getClass(), ID_FIELD_NAME); 
      buildCriteriaForSingleId(criteria); 
     } 

     Number one = castToSequenceNumberType(1L); 
     Number value = (Number) criteria.uniqueResult(); 

     if(value != null) { 
      value = castToSequenceNumberType(value.longValue() + one.longValue()); 

      setFieldValue(sequenceField, value, toSet); 
     } else { 
      value = one; 
      setFieldValue(sequenceField, value, toSet); 
     } 

     return identifiable.getId(); 
    } 

    private void buildCriteriaForSingleId(Criteria criteria) { 
     criteria.setProjection(Projections.max(ID_FIELD_NAME).as("seq")); 
    } 

    private void buildCriteriaForEmbeddedId(Serializable id, String embaddebleClassName, Criteria criteria) { 
     List<Field> fields = Arrays.asList(id.getClass().getDeclaredFields()); 

     class Utils { 
      Field field; 
      boolean numberFound = false; 
     } 
     final Utils utils = new Utils(); 

     for (Field field : fields) { 
      if ("serialVersionUID".equals(field.getName()) || "$jacocoData".equals(field.getName())) { 
       continue; 
      } 

      if (Number.class.isAssignableFrom(field.getType())) { 
       if (utils.numberFound) { 
        throw new IllegalArgumentException(
          embaddebleClassName + " has more then one sequence field: " + field.getName() + ", " 
            + utils.field.getName() + ",..."); 
       } 

       utils.numberFound = true; 
       utils.field = field; 
       sequenceField = field; 

       criteria.setProjection(Projections.max(ID_FIELD_NAME + "." + sequenceField.getName()).as("seq")); 
      } else { 
       criteria.add(Restrictions.eq(ID_FIELD_NAME + "." + field.getName(), getFieldValue(field, id))); 
      } 
     } 
    } 

    private Number castToSequenceNumberType(Number n) { 
     return (Number) sequenceField.getType().cast(n); 
    } 

    private void setFieldValue(Field field, Object value, Object to) { 
     try { 
      field.setAccessible(true); 
      field.set(to, value); 
     } catch (IllegalArgumentException | IllegalAccessException e) { 
      LOG.error(e.getMessage(), e); 
     } 
    } 

    private Object getFieldValue(Field field, Object from) { 
     try { 
      field.setAccessible(true); 
      return field.get(from); 
     } catch (IllegalArgumentException | IllegalAccessException e) { 
      LOG.error(e.getMessage(), e); 
     } 

     return null; 
    } 
} 

Customer.java

package my.app.entities; 

import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.Id; 
import org.hibernate.annotations.GenericGenerator; 

import my.app.hibernate.SingleKeyEntity; 

@Entity(name = "whatever_entity_name") 
@GenericGenerator(name = "WHATEVER_NAMED_GENERATOR", strategy = "my.app.hibernate.AssignedIdentityGenerator") 
public class Customer implements SingleKeyEntity<Long> { 

    @Id 
    @GeneratedValue(generator = "WHATEVER_NAMED_GENERATOR") 
    private Long id; 
    @Column(nullable = false) 
    private String name; 
} 

CustomerItemsId.java (Item.java ommited comme il résulte d'exemple SingleKeyEntity)

package my.app.entities; 

import javax.persistence.Embeddable; 
import javax.persistence.JoinColumn; 
import javax.persistence.ManyToOne; 

@Embeddable 
public class CustomerItemsId implements Serializable { 
    private static final long serialVersionUID = 1L; //generate one 

    @ManyToOne 
    @JoinColumn(name = "customer_id") 
    private Customer customer; 
    @ManyToOne 
    @JoinColumn(name = "item_id") 
    private Item item; 
    private Long seq; //name as you wish 
} 

CustomerItems.java

package my.app.entities; 

import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.Id; 
import org.hibernate.annotations.GenericGenerator; 

import my.app.hibernate.CompositeKeyEntity; 

@Entity(name = "whatever_entity_name") 
@GenericGenerator(name = "WHATEVER_NAMED_GENERATOR", strategy = "my.app.hibernate.AssignedIdentityGenerator") 
public class CustomerItems implements CompositeKeyEntity<CustomerItemsId> { 

    @GeneratedValue(generator = "WHATEVER_NAMED_GENERATOR") 
    private CustomerItems id; 
    @Column(nullable = false) 
    private String randomColumn1; 
    @Column(nullable = false) 
    private String randomColumn2; 
}