java - hibernate 在查询多对多关系时没有定位联结表

Question

在使用 hibernate 和 jpa 的 spring mvc 应用程序中，我在 WordKey 之间建立了多对多关系。实体和一个Concept实体。 WordKey有一个 concepts收集，和Concept有一个 wordkeys Collection 。我不想使用 fetchType=EAGER因为性能是一个问题。相反，一旦一个 WordKey已被用户选择，我想填充 Collection<Concept>使用 selectedKeyWord 的查询结果wk作为参数并返回 concepts 的集合与WordKey相关联在底层数据库中。如何在 JPQL 中编写此查询？

这是我目前的查询。它不起作用(请参阅下面的错误):

@SuppressWarnings("unchecked")
public Collection<Concept> findConceptsForKeyWord(ConcWordKey wk) {
    Query query = this.em.createQuery(
        "SELECT DISTINCT concept FROM Concept concept join concept.wordkeys k WHERE k.name =:wk"
    );
    query.setParameter("wk", wk.getName());
    Collection<Concept> result = (Collection<Concept>) query.getResultList();
    return result;
}

这是由上述代码生成的 hibernate 查询。请注意，它正在寻找一个虚构的 concept_wordkey表而不是使用 wordkey_junction WordKey 中指定的连接表下面是实体代码:

select distinct conc0_.effectiveTime as effectiv1_52_,
 conc0_.id as id2_52_,
 from concept conc0_
 inner join concept_wordkey wordkeys1_
 on conc0_.effectiveTime=wordkeys1_.concept_effectiveTime
 and conc0_.id=wordkeys1_.concept_id
 inner join wordkey conc2_
 on wordkeys1_.wordkeys_keyword=conc2_.keyword
 where conc2_.keyword=?

堆栈跟踪中生成的具体错误是:

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:  
Table 'mydb.concept_wordkey' doesn't exist

这是 Concept实体:

@Entity
@Table(name = "concept")
public class Concept implements Serializable{

    @EmbeddedId
    public EmbedPK conceptPk;

    @ManyToMany(cascade={CascadeType.ALL})
    private Set<WordKey> wordkeys;

    public EmbedPK getConceptPk(){return conceptPk;}

    protected Set<WordKey> getWordkeysInternal() {
        if (this.wordkeys == null) {this.wordkeys = new HashSet<WordKey>();}
        return this.wordkeys;
    }

    public List<WordKey> getWordkeys() {
        List<WordKey> sortedWordkeys = new ArrayList<WordKey>(getWordkeysInternal());
        PropertyComparator.sort(sortedWordkeys, new MutableSortDefinition("wordkey", true, true));
        return Collections.unmodifiableList(sortedWordkeys);
    }

    public WordKey getWordkey(String s) {return getWordkey(s, false);}

    public WordKey getWordkey(String ps, boolean ignoreNew) {
        ps = ps.toLowerCase();
        for (WordKey s1 : getWordkeysInternal()) {
            if (!ignoreNew || !s1.isNew()) {
                String keyword = s1.getName();
                keyword = keyword.toLowerCase();
                if (keyword.equals(ps)) {return s1;}
            }
        }
        return null;
    }
}

这是 WordKey实体:

@Entity
@Table(name = "wordkey")
public class WordKey {

    @Id
    @Column(name="keyword")
    private String name;

    @ManyToMany(cascade = {CascadeType.ALL})
    @JoinTable(name="wordkey_junction",
        joinColumns={@JoinColumn(name="keyword")},
        inverseJoinColumns={@JoinColumn(name="conceptid"),@JoinColumn(name="effectiveTime")})
    private Set<Concept> concepts = new HashSet<Concept>();

    public String getName(){return name;}
    public void setName(String nm){name=nm;}

    protected Set<Concept> getConceptsInternal() {
        if (this.concepts == null) {this.concepts = new HashSet<Concept>();}
        return this.concepts;
    }

    public List<Concept> getConcepts() {
        List<Concept> sortedConcepts = new ArrayList<Concept>(getConceptsInternal());
        PropertyComparator.sort(sortedConcepts, new MutableSortDefinition("conceptid", true, true));
        return Collections.unmodifiableList(sortedConcepts);
    }

    public Concept getConcept(BigInteger s) {return getConcept(s, false);}

    public Concept getConcept(BigInteger ps, boolean ignoreNew) {
        for (Concept s1 : getConceptsInternal()) {
            if (!ignoreNew || !s1.isNew()) {
                BigInteger compName = s1.getConceptPk().getId();
                if (compName == ps) {return s1;}
            }
        }
        return null;
    }
}

Answer 1

我认为您的 Concept 类中的 @ManyToMany(cascade={CascadeType.ALL}) 中需要一个 mappedBy。将注释添加到 @ManyToMany(cascade={CascadeType.ALL}, mappedBy="concepts") 并重试。

您需要这个来告诉 Hibernate 将您的多对多 wordKey 集合映射到 WordKey< 上的 Concept 集合 类，它将依次将您的 wordkey_junction 表公开给集合。

如果这不起作用或者您不想要双向关系，请告诉我。