Hibernate creating duplicate objects

Question

Hiberate is creating duplicate objects as a result of my inner join. The query joins the parent table with the child table (parent has a one to many relationship with child).

Data:

Category (Parent)
ID|Name
1|A
2|B

Testcase (Child)
ID|CategoryID|Name|Run
1|1|A|500
2|1|B|500
3|1|C|500
4|2|D|600

Result from join where run = 500

CategoryID|TestcaseID|TestCase Name
1|1|A
1|2|B
1|3|C

From this, I would expect Hibernate to create one Category object with a list containing 3 testcase objects. Instead it created 3 Category objects each with the correct list of 3 testcases

Category [ID=1, name=FOO, testCases=[TestCase [ID=1, name=A, runId=500], TestCase [ID=2, name=B, runId=500], TestCase [ID=3, name=C, runId=500]]]

Model:

@Entity
@Table(name = "CATEGORY")
public class Category implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "CATEGORYID")
    private int ID;

    @Column(name = "CATEGORYNAME")
    private String name;

    @OneToMany(fetch = FetchType.EAGER)
    @JoinColumn(name = "CATEGORYID")
    @Filter(name = "TEST_RUN_ID_FILTER")
    private Collection<TestCase> testCases;
}

@Entity
@Table(name = "TESTCASE_NEW")
@FilterDef(name = "TEST_RUN_ID_FILTER", defaultCondition = "TESTRUNID in (:IDS)", parameters = { @ParamDef(name = "IDS", type = "int") })
public class TestCase implements Serializable
{
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "TESTCASEID")
    private int ID;

    @Column(name = "TESTCASENAME")
    private String name;

    @Column(name = "STATUS")
    private String status;

    @Column(name = "TESTRUNID")
    private int testRunId;
}

DAO:

 public List<Category> getAllCategoriesForTestRuns(List<Integer> testRunIDs)
    {
        Session session = getSession();
        session.enableFilter("TEST_RUN_ID_FILTER")
                .setParameterList("IDS", testRunIDs);
        Query query = session.createQuery("select c from Category c inner join c.testCases tc");
        List<Category> result = query.list();
        return result;
    }

I am able to get the right result if I chage the HQL query to select distinct, but I am wondering if there is a more correct way. From my Googling, I tried adding @Fetch(FetchMode.SELECT) to the testCase list in Category but that had no effect.

Thanks!

Peter Bratton · Accepted Answer · 2013-03-19 19:03:00Z

2

Use a ResultTransformer:

Query query = session.createQuery("hql")
                  .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);

The issue is that your inner join will return an object for each entity in the testCases collection (as a DB query result set would for an inner join).

answered Mar 19, 2013 at 19:03

Peter Bratton

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1 Comment

raven-king Over a year ago

Very helpful thanks. It does make sense when you think of it as a result set! I'd been adding each resulting object to a set to filter out duplicates which always felt wrong.

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