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https://issues.apache.org/jira/browse/AIRAVATA-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16597873#comment-16597873
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Marcus Christie commented on AIRAVATA-2872:
-------------------------------------------
OpenJPA docs on attaching with null values:
{quote}
When attaching null fields in these cases, OpenJPA cannot distinguish between a
field that was unloaded and one that was intentionally set to null. In this
case, OpenJPA will use the current detach state setting to determine how to
handle null fields: fields that would have been included in the detached state
are treated as loaded, and will in turn set the corresponding attached field to
null.
{quote}
http://openjpa.apache.org/builds/2.4.3/apache-openjpa/docs/ref_guide_remote.html#ref_guide_attach_behavior
"Detach state" options are
{quote}
1. loaded: Detach all fields and relations that are already loaded, but don't
include unloaded fields in the detached graph. This is the default.
2. fetch-groups: Detach all fields and relations in the current fetch
configuration. For more information on custom fetch groups, see Section 7, “
Fetch Groups ”.
3. all: Detach all fields and relations. Be very careful when using this mode;
if you have a highly-connected domain model, you could end up bringing every
object in the database into memory!
{quote}
http://openjpa.apache.org/builds/2.4.3/apache-openjpa/docs/ref_guide_remote.html#ref_guide_detach_state
Looks like #3, *all*, is what we want. I don't think the warning is applicable
since we don't explicitly detach the entities, instead we translate them to
Thrift data model instances. I'll test this and see if it works.
> registry-refactoring: OpenJPA doesn't persist setting a field to null
> ---------------------------------------------------------------------
>
> Key: AIRAVATA-2872
> URL: https://issues.apache.org/jira/browse/AIRAVATA-2872
> Project: Airavata
> Issue Type: Bug
> Components: Registry API
> Reporter: Marcus Christie
> Assignee: Marcus Christie
> Priority: Major
>
> 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:
> {code:java}
> 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 {
> {code}
> 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.
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