Hibernate识别数据库特有字段实例详解

package framework.postgresql;

import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.usertype.UserType;
import org.postgresql.util.PGInterval;

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.time.Duration;

/**
 * PostgreSql Inteval字段与java.time.Duration映射
 * 目前只支持到最多1个月(30天)的间隔
 * <p>
 * 使用方法：
 * 在实体类上增加
 * \@TypeDef(name="interval", typeClass = IntervalType.class)
 * 在字段定义上增加:
 * \@Type(type = "interval")
 * <p>
 * http://stackoverflow.com/questions/1945615/how-to-map-the-type-interval-in-hibernate/6139581#6139581
 *
 * @version 1.0
 * @since 1.0
 */
public class IntervalType implements UserType {

 public Object assemble(Serializable cached, Object owner) throws HibernateException {
  return cached;
 }

 public Object deepCopy(Object value) throws HibernateException {
  return value;
 }

 public Serializable disassemble(Object value) throws HibernateException {
  return (Serializable) value;
 }

 public boolean equals(Object arg0, Object arg1) throws HibernateException {
  return arg0 != null && arg1 != null && arg0.equals(arg1) || arg0 == null && arg1 == null;
 }

 public int hashCode(Object object) throws HibernateException {
  return object.hashCode();
 }


 @Override
 public Object nullSafeGet(ResultSet resultSet, String[] names, SharedSessionContractImplementor sessionImplementor, Object o) throws HibernateException, SQLException {
  String interval = resultSet.getString(names[0]);
  if (resultSet.wasNull() || interval == null) {
   return null;
  }
  PGInterval pgInterval = new PGInterval(interval);

  return getDuration(pgInterval);
 }

 @Override
 public void nullSafeSet(PreparedStatement st, Object value, int index, SharedSessionContractImplementor sessionImplementor) throws HibernateException, SQLException {
  if (value == null) {
   st.setNull(index, Types.OTHER);
  } else {
   //this http://postgresql.1045698.n5.nabble.com/Inserting-Information-in-PostgreSQL-interval-td2175203.html#a2175205
   Duration duration = (Duration) value;
   st.setObject(index, getInterval(duration), Types.OTHER);
  }
 }

 public static Duration getDuration(PGInterval pgInterval) {
  return Duration.ofSeconds(pgInterval.getDays() * 24 * 3600  
    pgInterval.getHours() * 3600  
    pgInterval.getMinutes() * 60  
    (int) pgInterval.getSeconds());
 }

 private static PGInterval getInterval(Duration value) {
  long seconds = value.getSeconds();
  int days = (int) (seconds / (24 * 3600));
  seconds -= days * 24 * 3600;
  int hours = (int) (seconds / 3600);
  seconds -= hours * 3600;
  int minutes = (int) (seconds / 60);
  seconds -= minutes * 60;
  seconds = Math.abs(seconds);
  return new PGInterval(0, 0, days, hours, minutes, seconds);
 }


 public boolean isMutable() {
  return false;
 }


 public Object replace(Object original, Object target, Object owner) throws HibernateException {
  return original;
 }

 public Class returnedClass() {
  return Duration.class;
 }

 public int[] sqlTypes() {
  return new int[]{Types.OTHER};
 }

}

...
@Entity
@TypeDef(name = "interval", typeClass = IntervalType.class)
public class PaperStatis implements Serializable {
...
 @Column(name = "avg_duration")
 @Type(type = "interval")
 public Duration getAvgDuration() {
  return this.avgDuration;
 }
...
}