hibernate 实体类跟数据库关联 hql查询数据库中最新时间的数据

工作中遇到要查询一堆数据里面最新的那条数据，可以将最后更新时间last_update倒叙后输出。

数据库信息：

CREATE TABLE `xxx_info` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `xxx_id` varchar(10) DEFAULT NULL,
  `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT 'last_update time',
  `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT 'data create time',
  PRIMARY KEY (`id`),
  KEY `idx_xxx_id` (`xxx_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COMMENT='xxx_info message'

实体类跟数据库关联：

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
import org.hibernate.annotations.Type;
import org.joda.time.DateTime;

import javax.persistence.*;
import java.io.Serializable;

/**
 * Created by ziqi on 2017/11/29.
 */
@Entity
@Table(name="xxx_info")
public class XxxInfo  {
    @Expose(serialize = false, deserialize = false)
    @Id
    @Column(name = "id", updatable = false, unique = true, nullable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @SerializedName(value = "xxx_id",alternate = "xxxId")
    @Column(name = "xxx_id")
    private String xxxId;

    @Expose(serialize = false, deserialize = false)
    @Column(name = "last_update")
    @Type(type = "org.jadira.usertype.dateandtime.joda.PersistentDateTime")
    private DateTime lastUpdate;

    @Expose(serialize = false, deserialize = false)
    @Column(name = "create_time")
    @Type(type = "org.jadira.usertype.dateandtime.joda.PersistentDateTime")
    private DateTime createTime;

    @Override
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }


    public String getxxxId() {
        return xxxId;
    }

    public void setxxxId(String xxxId) {
        this.xxxId = xxxId;
    }

    public DateTime getLastUpdate() {
        return lastUpdate;
    }

    public void setLastUpdate(DateTime lastUpdate) {
        this.lastUpdate = lastUpdate;
    }

    public DateTime getCreateTime() {
        return createTime;
    }

    public void setCreateTime(DateTime createTime) {
        this.createTime = createTime;
    }
}

sql让数据库以倒叙输出语句如下：

通过 ”order by“实现，

语法 ：order by  字段  asc/desc,

备注：asc是表示升序，desc表示降序。

sql:select * from table_name order by column_name1 desc;
解释：上面语句的意思就是根据"column_name1"字段排序，倒叙输出table_name表中的数据。

HibernateDao处理

hibernate查询最新数据：

 Session session = getSessionFactory().openSession();

        try {
            Query query = session.createQuery("select v from VehicleInfo v where v.vin = :vin order by v.lastUpdate desc").setParameter("vin", vin);
            List<VehicleInfo> vehicleInfoList = query.list();
            return vehicleInfoList.get(0);
        } catch (Exception e) {
            LOGGER.error(e.getMessage());
            throw e;
        } finally {
            session.close();
        }

（from 后跟的是需要查询的实体类的名字,而不是数据库中对应表的名字,这点需要特别注意）

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