[AIRAVATA-2872] registry-refactoring: OpenJPA doesn't persist setting a field to null

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: Registry API
• Epic Link: Registry Refactoring
• Assignee: Marcus Christie
• Reporter: Marcus Christie
• Created: 17/Aug/18 20:09
• Updated: 09/Nov/18 16:04
• Resolved: 06/Nov/18 17:34

Description

In OpenJPA, the default handling of null values on detached instances is to treat them as "unloaded" when merging them, meaning it treats them as if they are simply missing instead of treating them as having been set to null. That is, it skips over null value and doesn't update the corresponding fields on the persistent instances to have a null value.

See https://stackoverflow.com/a/2569417/1419499

See also official docs: http://openjpa.apache.org/builds/2.4.3/apache-openjpa/docs/ref_guide_remote.html#ref_guide_detach, however it's hard to understand how to make use of this in our context.

See also this discussion http://openjpa.208410.n2.nabble.com/null-values-not-updating-td3224059.html

I traced the OpenJPA code to these lines in VersionAttachStrategy:

        int detach = (isNew) ? DETACH_ALL : broker.getDetachState();
        FetchConfiguration fetch = broker.getFetchConfiguration();
        try {
            FieldMetaData[] fmds = sm.getMetaData().getFields(); 
            for (int i = 0; i < fmds.length; i++) {
                switch (detach) {
                    case DETACH_ALL:
                        attachField(manager, toAttach, sm, fmds[i], true);
                        break;
                    case DETACH_FETCH_GROUPS:
                        if (fetch.requiresFetch(fmds[i]) 
                            != FetchConfiguration.FETCH_NONE)
                            attachField(manager, toAttach, sm, fmds[i], true);
                        break;
                    case DETACH_LOADED:
                        attachField(manager, toAttach, sm, fmds[i], false);
                        break;
                }
            }
        } finally {

The detach state is DETACH_LOADED which causes OpenJPA to treat nulls as unloaded and thus it skips merging those values in.

I think with a configuration change we can get this to work, but it's not obvious what all the flags mean, so this will take some research.

One other question I have, is how did this work before. It would be worth checking to see how the old registry code had configured OpenJPA.

Issue Links

• is related to: AIRAVATA-2939 gateway_id set to null when application interface updated
• relates to: AIRAVATA-2751 Dozer custom mapping to skip primitive fields that aren't set