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我在 WebSphere Application Server 8 上使用 OpenJPA 2.1。我有一个双向 oneToMay 关系，如下所示：

@Entity(name = "table1")
public class Table1  {
    @Id
    @Column(columnDefinition = "DATE")
    private Date date;
    @OneToMany(mappedBy = "date", targetEntity = Table2.class, fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)
    private List<Table2> table2List;
}

@Entity(name = "table2")
public class Tabl2{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "fk_date", nullable = false)
    private Table1 table1;

    @Column(name = "value", nullable = false, columnDefinition = "INT")
    private int value;

}

现在我想在 table2 上选择整个 table1 实体，如下所示：

TypedQuery<WeekBean> q = em.createQuery(
    "SELECT t1 from table1 t1 JOIN FETCH t1.table2List t2 WHERE t2.value = :value",
    t1.class);

但这不起作用，因为我得到一个 ArgumentException：

Exception in thread "main" <openjpa-2.1.1-SNAPSHOT-r422266:1141200 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: " Encountered "f" at character 50, but expected [",", ".", "GROUP", "HAVING", "INNER", "JOIN", "LEFT", "ORDER", "WHERE", <EOF>]." 
    at org.apache.openjpa.kernel.jpql.JPQLParser.parse(JPQLParser.java:51)
    at org.apache.openjpa.kernel.ExpressionStoreQuery.newCompilation(ExpressionStoreQuery.java:154)
    at org.apache.openjpa.datacache.QueryCacheStoreQuery.newCompilation(QueryCacheStoreQuery.java:262)
    at org.apache.openjpa.kernel.QueryImpl.newCompilation(QueryImpl.java:672)
    at org.apache.openjpa.kernel.QueryImpl.compilationFromCache(QueryImpl.java:654)
    at org.apache.openjpa.kernel.QueryImpl.compileForCompilation(QueryImpl.java:620)
    at org.apache.openjpa.kernel.QueryImpl.compileForExecutor(QueryImpl.java:682)
    at org.apache.openjpa.kernel.QueryImpl.compile(QueryImpl.java:589)
    at org.apache.openjpa.persistence.EntityManagerImpl.createQuery(EntityManagerImpl.java:996)
    at com.ibm.ws.persistence.EntityManagerImpl.createQuery(EntityManagerImpl.java:107)
    at com.ibm.ws.persistence.EntityManagerImpl.createQuery(EntityManagerImpl.java:86)
    at com.ibm.ws.persistence.EntityManagerImpl.createQuery(EntityManagerImpl.java:34)
    at org.apache.openjpa.persistence.EntityManagerImpl.createQuery(EntityManagerImpl.java:974)

如何在集合上使用带有条件的 JOIN FETCH？

最好的问候投票

4

1 回答 1

3

根据 JPA 2.0 规范，不支持这样的构造，并且看起来 OpenJPA 也不提供作为供应商扩展的功能：

FETCH JOIN 子句右侧引用的关联必须是属于作为查询结果返回的实体的关联。不允许为 FETCH JOIN 子句右侧引用的实体指定标识变量，因此对隐式获取的实体的引用不能出现在查询的其他地方。

在您的情况下，这意味着您无法定义t2，因此您无法在 WHERE 子句中使用它。

于 2012-07-19T07:17:55.493 回答