PostgreSQL 枚举和 Java 枚举之间的Hibernate 映射

出身背景

• 春天3.x、 JPA 2.0，Hibernate 4.x、 Postgresql 9.十、
• 正在处理Hibernate映射类，该类具有要映射到Postgresql枚举的枚举属性.

问题

使用枚举列上的where子句进行查询会引发异常.

org.hibernate.exception.SQLGrammarException: could not extract ResultSet
... 
Caused by: org.postgresql.util.PSQLException: ERROR: operator does not exist: movedirection = bytea
  Hint: No operator matches the given name and argument type(s). You might need to add explicit type casts.

代码(高度简化)

SQL:

create type movedirection as enum (
    'FORWARD', 'LEFT'
);

CREATE TABLE move
(
    id serial NOT NULL PRIMARY KEY,
    directiontomove movedirection NOT NULL
);

Hibernate映射类:

@Entity
@Table(name = "move")
public class Move {

    public enum Direction {
        FORWARD, LEFT;
    }

    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "sequenceGenerator", strategy=GenerationType.SEQUENCE)
    @SequenceGenerator(name = "sequenceGenerator", sequenceName = "move_id_seq")
    private long id;

    @Column(name = "directiontomove", nullable = false)
    @Enumerated(EnumType.STRING)
    private Direction directionToMove;
    ...
    // getters and setters
}

调用查询的Java:

public List<Move> getMoves(Direction directionToMove) {
    return (List<Direction>) sessionFactory.getCurrentSession()
            .getNamedQuery("getAllMoves")
            .setParameter("directionToMove", directionToMove)
            .list();
}

Hibernate xml查询:

<query name="getAllMoves">
    <![CDATA[
        select move from Move move
        where directiontomove = :directionToMove
    ]]>
</query>

故障排除

• 按id而不是按枚举进行查询，效果与预期一样.

• 没有数据库交互的Java运行良好:

  public List<Move> getMoves(Direction directionToMove) {
      List<Move> moves = new ArrayList<>();
      Move move1 = new Move();
      move1.setDirection(directionToMove);
      moves.add(move1);
      return moves;
  }
  

• createQuery没有使用XML进行查询，类似于Apache's JPA and Enums via @Enumerated documentation中的findByRating示例给出了相同的异常.
• 在psql中查询select * from move where direction = 'LEFT';项工作正常.
• Hardcoding 100 in the query in the XML works.

• 与.setString()和.setText()相同，.setParameter("direction", direction.name())不会将异常更改为:

  Caused by: org.postgresql.util.PSQLException: ERROR: operator does not exist: movedirection = character varying
  

试图解决问题

• 此公认答案https://stackoverflow.com/a/1594020/1090474建议的定制UserType以及:

  @Column(name = "direction", nullable = false)
  @Enumerated(EnumType.STRING) // tried with and without this line
  @Type(type = "full.path.to.HibernateMoveDirectionUserType")
  private Direction directionToMove;
  

• 与Hibernate的EnumType进行映射，如上面同一个问题中评分较高但未被接受的答案https://stackoverflow.com/a/1604286/1090474所示，以及:

  @Type(type = "org.hibernate.type.EnumType",
      parameters = {
              @Parameter(name  = "enumClass", value = "full.path.to.Move$Direction"),
              @Parameter(name = "type", value = "12"),
              @Parameter(name = "useNamed", value = "true")
      })
  

  有无两个秒参数，在看到https://stackoverflow.com/a/13241410/1090474后

• 试着在答案https://stackoverflow.com/a/20252215/1090474中注释getter和setter.
• 我没有试过EnumType.ORDINAL，因为我想坚持EnumType.STRING，它不那么脆弱，也更灵活.

其他注释

JPA2.1类型转换器应该不是必需的，但无论如何都不是一个选项，因为我现在正在使用JPA2.0.