jpa中具有取数关系的计数查询

Question

public class ArticleType extends BaseEntity implements Serializable
{
    private static final long   serialVersionUID    = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "art_typ_index")
    private Integer             artTypIndex;
    //@Basic(optional = false)
    @Column(name = "art_typ_code", nullable = false)
    private String              artTypCode;
    @OneToMany(mappedBy = "artArtTypIndex", fetch = FetchType.LAZY)
    private Set<Article>        articleSet;

    public ArticleType()
    {
    }

    public ArticleType(Integer artTypIndex)
    {
        this.artTypIndex = artTypIndex;
    }

    public ArticleType(Integer artTypIndex, String artTypCode)
    {
        this.artTypIndex = artTypIndex;
        this.artTypCode = artTypCode;
    }

    public Integer getArtTypIndex()
    {
        return artTypIndex;
    }

    public void setArtTypIndex(Integer artTypIndex)
    {
        this.artTypIndex = artTypIndex;
    }

    public String getArtTypCode()
    {
        return artTypCode;
    }

    public void setArtTypCode(String artTypCode)
    {
        this.artTypCode = artTypCode;
    }

    @XmlTransient
    public Set<Article> getArticleSet()
    {
        return articleSet;
    }

    public void setArticleSet(Set<Article> articleSet)
    {
        this.articleSet = articleSet;
    }   
}

SELECT 
count(articleType.artTypIndex)
FROM
ArticleType articleType 
join fetch articleType.articleSet article
where articleType.artTypCode = ?

我不明白是什么问题？
谢谢。

Answer 1

问题是您选择的是计数，而不是实体，而是连接提取。

您不需要急切地用您没有获取的实体加载集合。

试着只使用join。