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https://issues.apache.org/jira/browse/OPENJPA-3017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18130320#comment-18130320
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ASF subversion and git services commented on OPENJPA-3017:
----------------------------------------------------------
Commit c1cb1a964f9d80e43340723d020a53a1fd3589ad in openjpa's branch
refs/heads/OPENJPA-3017 from Richard Zowalla
[ https://gitbox.apache.org/repos/asf?p=openjpa.git;h=c1cb1a964 ]
[OPENJPA-3017] Put a mapping file column of a basic collection on the attribute
A <column> inside <basic> on a collection or map was assigned to the
element mapping unless the value was serialized. A collection converted
as a whole then failed to map with "this mapping cannot have columns in
this context". A basic attribute is one value with one column, so its
column now belongs to the attribute. The converter cannot decide this
here, since an @Convert annotation is not parsed yet.
> @Convert on a collection attribute is ignored and the attribute is silently
> not persisted
> -----------------------------------------------------------------------------------------
>
> Key: OPENJPA-3017
> URL: https://issues.apache.org/jira/browse/OPENJPA-3017
> Project: OpenJPA
> Issue Type: Bug
> Affects Versions: 4.1.1
> Reporter: Richard Zowalla
> Assignee: Richard Zowalla
> Priority: Major
>
> An {{@Convert}} annotation on a collection-valued attribute is not honoured,
> and the attribute is silently excluded from the mapping. Neither an exception
> nor an error is raised, and the data is lost without notice.
> Reduced case: an entity declaring
> {code:java}
> @Convert(converter = ItemListConverter.class)
> private List<Item> items = new ArrayList<>();
> {code}
> where {{ItemListConverter}} implements {{AttributeConverter<List<Item>,
> String>}} and {{Item}} is a plain bean. Observed behaviour on 4.2.0-SNAPSHOT
> with Derby:
> * {{ClassMapping.getField("items")}} returns {{null}}, so the field is not a
> managed field at all;
> * no column is generated for it;
> * a {{persist()}} followed by a {{find()}} in a fresh context returns an
> empty list, with no exception at any point;
> * the sole trace is one warning stating that the field is "not a default
> persistent type, and do not have any annotations indicating their persistence
> strategy", from which it follows that {{@Convert}} is not counted as an
> indication of a persistence strategy. In a run of the full test suite several
> hundred such warnings are emitted, so the one that matters is easily missed.
> Two defects follow. First, {{@Convert}} should be recognised as declaring a
> persistence strategy. Second, where the conversion cannot be applied, the
> attribute must not be dropped in silence; an error naming the attribute and
> the reason is required.
> On the specified semantics: {{@Convert}} applied to a collection attribute
> other than a {{Map}}, with no {{attributeName}}, converts the *elements* of
> the collection, which would require {{AttributeConverter<Item, ?>}} together
> with {{@ElementCollection}}. A converter whose attribute type is the
> collection itself, mapping the whole collection to a single column, is a
> provider extension; Hibernate admits it. Whichever reading is implemented,
> the present behaviour is wrong, because an unsupported mapping is accepted
> and then ignored.
> Reported on the development list by Francesco Chicchiriccò while testing
> Apache Syncope master against 4.2.0-SNAPSHOT. In that configuration the
> attribute is managed and the failure is instead
> {noformat}
> org.apache.openjpa.util.MetaDataException: You have supplied columns for
> "...JPARealm.plainAttrs<element:class ...PlainAttr>", but this mapping cannot
> have columns in this context.
> at
> org.apache.openjpa.jdbc.meta.MappingInfo.assertNoSchemaComponents(MappingInfo.java:384)
> at
> org.apache.openjpa.jdbc.meta.strats.HandlerFieldStrategy.map(HandlerFieldStrategy.java:84)
> {noformat}
> which arises because the handler derived from the converter is installed and
> the element mapping is then found to carry columns. That path did not
> reproduce from the annotations alone, neither with a {{Serializable}} element
> type nor with a non-final field, and the configuration difference is still to
> be established. The message is in any case opaque with respect to the cause.
> A workaround exists and was verified: the converted form serves as the
> persistent attribute, that is a {{String}} column holding the serialised
> value, the collection is marked {{@Transient}}, and the two directions are
> carried out in {{@PrePersist}}/{{@PreUpdate}} and {{@PostLoad}}. The OpenJPA
> extensions {{@Externalizer}} and {{@Factory}} offer no alternative, as
> {{@Persistent}} rejects a field of {{List}} type.
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