java - 如何在 Hibernate 中内连接两个独立实体

Question

我有 2 个实体:DocumentEntity(docNumber(主键)、dateOfFill，...) 和 FileEntity(id、标题、大小、...)。我有一个内连接为 2 的 HQL 查询，它应该在 Oracle DB 上运行:

String queryStr = "SELECT docNumber " +
             + "FROM DocumentEntity d " +
             + "INNER JOIN FileEntity f " +
             + "ON d.docNumber = f.title " +
             + "WHERE d.date > to_date('01.01.2011','dd.mm.yyyy')"

Query query = em.createQuery(query_string);
return query.getResultList();

当我运行代码片段时，我收到异常org.hibernate.hql.ast.QuerySyntaxException:加入的路径预期!

我看过了

• Hibernate 4.3.6 QuerySyntaxException: Path expected for join
• HQL ERROR: Path expected for join
• Path Expected for Join! Nhibernate Error
• HQL Hibernate INNER JOIN

但没有解决我的问题。本示例中无法使用建议的路径(至少它会给出错误的路径错误)。最后一个链接的答案是:

Joins can only be used when there is an association between entities.

问题是我无法关联这两个实体。

问题是:我如何加入这两个实体？

更新:我的实体是:

@Entity
@Table(name = "DOCUMENT")
public class DocumentEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "DOC_NUMBER", nullable = false)
    private String docNumber;

    @Basic(optional = false)
    @Column(name = "DATE_OF_FILL")
    @Temporal(TemporalType.DATE)
    private Date dateOfFill;

    ...
}

和

@Entity
@Table(name = "FS_FILE")
public class FileEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "FS_FILE_SEQ", allocationSize = 1, sequenceName = "FS_FILE_SEQ")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "FS_FILE_SEQ")
    @Column(name = "ID", nullable = false)
    protected Long id;

    @Column(name = "TITLE", nullable = false)
    protected String title;

    @Column(name = "MIMETYPE", nullable = false)
    protected String mimetype;

    @Column(name = "FILESIZE", nullable = false)
    protected Long filesize;

    @Column(name = "FILEPATH", nullable = false)
    protected String filepath;

    ...
}

Answer 1

在这种情况下，您不需要执行联接，因为您使用条件 d.docNumber = f.title 限制结果。只需在 where 子句中添加条件并使用 SQL 查询而不是 JPQL 查询，因为它似乎更符合您的需求。

String sqlString= "SELECT d.docNumber " +
             + "FROM DOCUMENT d, FS_FILE f " +
             + "WHERE d.docNumber = f.title " +
             + "AND d.date > to_date('01.01.2011','dd.mm.yyyy')"


Query query = em.createNativeQuery(sqlString);
return query.getResultList();