Persistence

Feb 4th, 2018

Java Type to JDBC Type

JAVA TYPE	JDBC TYPE
java.time.LocalDate	DATE
java.time.LocalTime	TIME
java.time.LocalDateTime	TIMESTAMP
java.time.OffsetTime	TIME_WITH_TIMEZONE
java.time.OffsetDateTime	TIMESTAMP_WITH_TIMEZONE
java.time.Duration	BIGINT
java.time.Instant	TIMESTAMP
java.time.ZonedDateTime	TIMESTAMP

Changing Persistence Unit dynamically

Keep the persistence unit file (Persistence.xml) as it’s. You can override the properties in it as follows.

EntityManagerFactory managerFactory = null;
Map<String, String> persistenceMap = new HashMap<String, String>();

persistenceMap.put("javax.persistence.jdbc.url", "<url>");
persistenceMap.put("javax.persistence.jdbc.user", "<username>");
persistenceMap.put("javax.persistence.jdbc.password", "<password>");
persistenceMap.put("javax.persistence.jdbc.driver", "<driver>");

managerFactory = Persistence.createEntityManagerFactory("<current persistence unit>", persistenceMap);
manager = managerFactory.createEntityManager();

Bulk update with JPA CriteriaUpdate

public void bulkUpdatePricesInLocal() {
    CriteriaBuilder cb = em.getCriteriaBuilder();
    CriteriaUpdate<ProductEntity> cu = cb.createCriteriaUpdate(ProductEntity.class);
    Root<ProductEntity> root = cu.from(ProductEntity.class);
    Join<ProductEntity, CurrencyEntity> currencyToConsumer = root.join(ProductEntity_.currencyToConsumer);
    Join<ProductEntity, CurrencyEntity> currencyToRetailer = root.join(ProductEntity_.currencyToRetailer);

    Expression<BigDecimal> prodConsumer = cb.prod(root.<BigDecimal>get(ProductEntity_.priceToConsumer), currencyToConsumer.<BigDecimal>get(CurrencyEntity_.rateTCMB));
    Expression<BigDecimal> prodRetailer = cb.prod(root.<BigDecimal>get(ProductEntity_.priceToRetailer), currencyToRetailer.<BigDecimal>get(CurrencyEntity_.rateTCMB));

    cu.set(root.get(ProductEntity_.priceToConsumerInLocal), prodConsumer);
    cu.set(root.get(ProductEntity_.priceToRetailerInLocal), prodRetailer);

    Query query = em.createQuery(cu);
    int resultList = query.executeUpdate();
}

Many-many relationship with extra columns in JPA

@Embeddable
public class DeveloperProjectId implements Serializable {
 
    private Long developerId;
    private Long projectId;

    // constructor, getters, setters
}

@Entity
public class DeveloperProject implements Serializable {
 
    @EmbeddedId
    private DeveloperProjectId developerProjectId;
 
    @ManyToOne
    @MapsId("developerId")
    private Developer developer;
 
    @ManyToOne
    @MapsId("projectId")
    private Project project;
 
    @Column
    private String task;

    // constructor, getters, setters
}

@Entity
public class Developer implements Serializable {
 
    @Id
    @GeneratedValue
    private Long id;
 
    private String name;
 
    @OneToMany(mappedBy = "developer")
    private List<DeveloperProject> projects;

    // constructor, getters, setters
}

@Entity
public class Project implements Serializable {
 
    @Id
    @GeneratedValue
    private Long id;
 
    @Column
    private String name;
 
    @OneToMany(mappedBy = "project")
    private List<DeveloperProject> developers;

    // constructor, getters, setters
}

CriteriaBuilder join two tables with a custom condition

CriteriaQuery<A> searchQuery = criteriaBuilder.createQuery(A.class);
Root<A> aRoot = searchQuery.from(A.class);
Join<A, B> bJoin= aRoot.join("mappedB", JoinType.LEFT);
bJoin.on(criteriaBuilder.equal(bJoin.get("idLanguage"), 22));

equal to

LEFT OUTER JOIN B ON A.ID = B.A_ID AND B.idLanguage = 22