java - 如何在 JPA 中选择和订购 EmbeddedID

Question

我有一个带有复合主键的表:

public class IdmTenantBoard implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private IdmTenantBoardPK id;

@Column(name="board_display_name")
private String boardDisplayName;

@Column(name="board_name")
private String boardName;

嵌入类如下所示:

public class IdmTenantBoardPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

@Column(name="board_id")
private int boardId;

@Column(name="tenant_id")
private String tenantId;

我用来调用查询的方法如下:

public String getMaxBoardId(){
      TypedQuery<String> query = entityManager.createQuery("select o from IdmTenantBoard o order by o.IdmTenantBoardPK.boardId desc",String.class);
      query.setMaxResults(1);
      List<String> lResults = query.getResultList();
      String maxBoardId=null;
      if((null!=lResults)&&(!lResults.isEmpty())){
          maxBoardId=lResults.get(0);
      }
      return maxBoardId;
}

我需要什么才能让 boardId 按降序排序？我收到以下错误:

Caused by: org.hibernate.QueryException: could not resolve property: IdmTenantBoardPK of: com.newrubric.idm.common.entities.IdmTenantBoard [select o from com.newrubric.idm.common.entities.IdmTenantBoard o order by o.IdmTenantBoardPK.boardId desc]

Answer 1

下面的IdmTenantBoardPK是嵌入id的类型，属性的名称是id:

@EmbeddedId
private IdmTenantBoardPK id;

这就是为什么 o.IdmTenantBoardPK.boardId 不能在查询中使用的原因。应该使用 o.id.boardId 来代替它。