How to return hibernate collection entities without returning root entity

Question

I would like to get elements of a collection (Set<SheetConfig>) for a set of objects (WorkbookConfig) from Hibernate without getting the primary objects(WorkbookConfig).

The underlying tables look like this:

workbook_config -> workbook_config_sheet_join <- sheet_config

If I just run it in my SQL utility, a successful SQL statement looks like this:

SELECT DISTINCT sheet_config_id FROM sheet_config AS sc 
    LEFT JOIN workbook_config_sheet_join AS wcsj 
       ON sc.sheet_config_id = wcsj.sheet_config_id
    LEFT JOIN workbook_config AS wc 
       ON wc.workbook_config_id = wcsj.workbook_config_id
WHERE wc.group_id ="1"
ORDER BY sheet_name;

I would like to do this properly without using HQL.

My UNSUCCESSFUL attempt has resulted in this:

@SuppressWarnings("unchecked")
public List<SheetConfig> findAllForUser() {

    List<SheetConfig> sheetConfigs = null;
    Session session = getSession();

    Criteria crit = session.createCriteria(WorkbookConfig.class)
            .add(Restrictions.in(GROUP, getGroupsForUser()))
            .setFetchMode(SHEET_CONFIGS, FetchMode.JOIN);

    sheetConfigs = (List<SheetConfig>) crit.list();

    return sheetConfigs;
}

This is still giving me WorkbookConfigs, but what I would like to do in a single pass is get SheetConfigs. I have spent the day on the Internet trying to find a coherent explanation of the Hibernate API, and I haven't been able to find what I would think is a solution to a fairly common requirement. I can always back out and just do most of the work in Java, but it seems like I should be able to do this with the Hibernate API. I appreciate any help, and also, if you can recommend a reference that explains not simply querying collections, but returning them, I would be grateful.

score 0 · Answer 1 · answered Sep 13 '14 at 22:49

0

Did you look into the setProjection method on Criteria? Using the setProjection method lets you select properties or objects from the executed query.

Hibernate Criteria documentation

answered Sep 13 '14 at 22:49

Mathias G.

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Unfortunately, this is not correct. The setProjection method only works on simple parameters, not on Sets. – Organus Sep 15 '14 at 15:04
Did you try something like Projections.projectionList() and add this list as your Criteria projection? – Mathias G. Sep 15 '14 at 15:29
Projections do not work on Collections.--See the note in this reference: http://stackoverflow.com/questions/18060880/getting-collections-using-projectionhibernate – Organus Sep 15 '14 at 19:24

How to return hibernate collection entities without returning root entity

1 Answers1