JPA

Replacements

java.util.Date     => java.time.Instant
java.sql.Timestamp => java.time.Instant
java.sql.Date      => java.time.LocalDate
java.sql.Time      => java.time.LocalTime

The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).All three java.time.Local… classes are all lacking any concept of time zone or offset-from-UTC.

Sequence Style

@Id
@Column(name = "code", length = 6)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "page_sqn")
//@SequenceGenerator(name = "page_sqn", sequenceName = "page_sqn", initialValue = 60466176, allocationSize = 1)
@GenericGenerator(name  = "page_sqn", strategy = "org.chorke.academia.core.entity.Base36Style", parameters = {
    @Parameter(name = Base36Style.INITIAL_VALUE,   value = Base36Style.DIGIT_6_MIN),
    @Parameter(name = Base36Style.SEQUENCE_NAME,   value = "page_sqn"),
    @Parameter(name = Base36Style.ALLOCATION_SIZE, value = "1"),
})
private String code;

package org.chorke.academia.core.entity;

import java.io.Serializable;
import java.util.Properties;

import org.hibernate.HibernateException;
import org.hibernate.MappingException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.enhanced.SequenceStyleGenerator;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.type.Type;

public class Base36Style extends SequenceStyleGenerator {
    private static final Logger LOG = LoggerFactory.getLogger(Base36Style.class);
    public static final String ALLOCATION_SIZE = INCREMENT_PARAM;
    public static final String SEQUENCE_NAME   = SEQUENCE_PARAM;
    public static final String INITIAL_VALUE   = INITIAL_PARAM;
    public static final int    RADIX = 36;

    public static final String DIGIT_1_MIN = "0";               //            0 =>             Z
    public static final String DIGIT_2_MIN = "36";              //           10 =>            ZZ
    public static final String DIGIT_3_MIN = "1296";            //          100 =>           ZZZ
    public static final String DIGIT_4_MIN = "46656";           //        1,000 =>         Z,ZZZ
    public static final String DIGIT_5_MIN = "1679616";         //       10,000 =>        ZZ,ZZZ
    public static final String DIGIT_6_MIN = "60466176";        //      100,000 =>       ZZZ,ZZZ
    public static final String DIGIT_7_MIN = "2176782336";      //    1,000,000 =>     Z,ZZZ,ZZZ
    public static final String DIGIT_8_MIN = "78364164096";     //   10,000,000 =>    ZZ,ZZZ,ZZZ
    public static final String DIGIT_9_MIN = "2821109907456";   //  100,000,000 =>   ZZZ,ZZZ,ZZZ
    public static final String DIGIT_X_MIN = "101559956668416"; //1,000,000,000 => Z,ZZZ,ZZZ,ZZZ

    @Override
    public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
        Serializable nextval = super.generate(session, object);
        String base36 = Long.toString((Long) nextval, RADIX);
        LOG.debug("Base36: {}", base36.toUpperCase());
        return base36.toUpperCase();
    }

    @Override
    public void configure(Type type, Properties params, ServiceRegistry serviceRegistry) throws MappingException {
        super.configure(LongType.INSTANCE, params, serviceRegistry);
    }
}

Challenges

Database	Auto Increment	Sequence	Usable
DB2/LUW	✓	✓	✓
DB2/z	✓	✓	✓
PostgreSQL	✓	✓	✓
Derby	✕	✓	✓
Firebird	✕	✓	✓
H2	✓	✓	✓
HyperSQL	✓	✓	✓
INGRES	✓	✕	✕
Informix	✓	✓	✓
MariaDB	✓	✕	✕
MySQL	✓	✕	✕
Oracle	✕	✓	✓
Sql Server	✕	✓	✓
SQLite	✓	✕	✕
Sybase	✓	✕	✕
Sybase Anywhere	✓	✓	✓

Date Time

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

class Playground {
    public static void main(String[ ] args) {
        System.out.println("Yesterday Min: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).minusDays(1L));
        System.out.println("Yesterday Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).minusNanos(1L));
        System.out.println("Yesterday Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).minusDays(1L).plusDays(1L).minusNanos(1L));
        System.out.println("Yesterday Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).minusDays(1L).plusHours(24).minusNanos(1L));

        System.out.println();
        System.out.println("Today    Min: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS));
        System.out.println("Today    Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).plusDays(1L).minusNanos(1L));
        System.out.println("Today    Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).plusHours(24).minusNanos(1L));

        System.out.println();
        System.out.println("Tomorrow Min: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).plusDays(1L));
        System.out.println("Tomorrow Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).plusDays(2L).minusNanos(1L));
        System.out.println("Tomorrow Max: " + LocalDateTime.now().truncatedTo(ChronoUnit.DAYS).plusHours(48).minusNanos(1L));
    }
}

Knowledge

import org.hibernate.Session; Session session = (Session) entityManager.getDelegate(); Page<Country> countries = countryRepo.findAll(page); countries = countries.map(country -> { session.evict(country); if (ObjectUtils.isEmpty(country.getContinent())) { Continent continent = continentRepo.findById(country.getContinentCode()); country.setContinent(continent); return country; } else return country; });
@PersistenceContext EntityManager entityManager; if (entityManager.contains(country)) entityManager.detach(country); // entityManager.detach(country);

References

Serialize/deserialize java.time with Jackson Usage OrderBy with findAll in Spring Data Never use the TABLE identifier generator Convention for Database Tables Java Persistence/Inheritance EclipseLink Hibernate DBUnit MyBatis Locale	Choosing between java.util.Date or java.sql.Date Integration of MyBatis & JPA in Spring boot Custom Sequence Based ID Generator Auto Increment Supported Database SQLite3 Doesn't Provide a Date Type JPA use hbm.xml & annotations JPA & SQLite3 - Wrong Date How to generate Custom Id JPA Primary Key Prefix Java Date vs Calendar	Prevent Jackson to Serialize Non-Fetched Lazy Objects Does JPA delete also remove large objects of Blob fields Using MySQL table to simulate Oracle Sequence Calling Stored Procedures from Spring Data JPA Multiple SequenceGenerator in Hibernate Entity @SequenceGenerator for MySql Database Create Sequence Supported Database Vlad Mihalcea the Java Champion Example of Stored Procedure Liquibase
Spring JPA ExampleMatcher compare date condition Difference btn. evict and detach in hibernate Column type is JSON but expression is Varchar Map a JSON column with H2 & Spring JPA Ignore Hibernate @Where annotation Java » ISO DateTimeFormatter Use @Where in Hibernate PostgreSQL MapStruct Lombok