如何在不使用 nativeQuery 的情况下在 JPA 上转换它？

Question

on my database I have a column where ack_date_time is stored(but in string), Im not the one who start this model and he saves the date on string on gmt example: Tue Aug 04 16:58:27 GMT+08:00 2015 , now we have large amount of data so I dont want to change it as date field as much as possible. how can I change this query statement on jpa without using native query? I manage to order by it on mysql but not on jpa. im a little bit new to it. thanks in advance.

select *, STR_TO_DATE(CONCAT(SUBSTR(ack_date_time,1,20),SUBSTR(ack_date_time,31,34)),'%W %M %D %H:%i:%s %Y') as acktime from DEMI order by acktime desc;

Answer 1

If I understood correctly, the DB level data type of ack_date_time column is VARCHAR , isn't it?

If it is, you can try AttributeConverter , see example here: http://www.thoughts-on-java.org/jpa-21-how-to-implement-type-converter/

You can define your own attribute converter as follows:

@Converter
public class DemiDateConverter implements AttributeConverter<Timestamp, String> {

 /**
  * Convert Timestamp object to a String.
  */
 @Override
 public String convertToDatabaseColumn(Timestamp ts) {
  // here you should implement the logic which converts the Timestamp to DB compatible format
 }

 /**
  * Convert a String to a Timestamp object.
  */
 @Override
 public Timestamp convertToEntityAttribute(String str) {
  // here you should implement the logic that parses string from DB and transforms it to regular timestamp.
 }
}

Then you need to use the converter in your entity class:

@Entity
public class DemiEntity {

   // id and other fields

   @Column(name = "ack_date_time")
   @Convert(converter = DemiDateConverter.class)
   private Timestamp acktime;

   // getters and setters
   ...
}

BTW, have you already tried to use JPA entity for DEMI table?