[jira] [Comment Edited] (OPENJPA-2429) NPE was thrown out when a @OrderBy modified column is being persisted.

["Frej Bjon (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-2429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16983433#comment-16983433 ] 

Frej Bjon edited comment on OPENJPA-2429 at 11/27/19 11:27 AM:
---------------------------------------------------------------

It seems this bug can indeed show up even if all applicable fields have @OrderBy-annotations. In the following abbreviated example, trying to update (merge) an existing Element-entity after starting up the system results in this same NPE. However, persisting an ElementGroup causes the relevant internal metadata fields to be populated (i.e. {{_orderDec}}, and everything works after that. There is no workaround that I can see short of using reflection to mess with the OpenJPA internals. The patch by [~jmntn2000] should work in this case too.

 
{noformat}
@Entity
public class Element {

	@OneToMany(cascade=CascadeType.PERSIST, mappedBy="element", fetch=FetchType.LAZY )
	@OrderBy("order asc")
	private List<PageElement> pageElement;
	
	@Column(name = "NAME", length=255)
	private String name;
	
	@ManyToOne( fetch=FetchType.EAGER )
	private ElementGroup elementGroup;
}

@Entity
public class PageElement {

	@Column( name="ORDER" )
	private Long order;

	@ManyToOne( fetch=FetchType.EAGER )
	private Element element;
}

@Entity
public class ElementGroup {

	@OneToMany(cascade=CascadeType.ALL, mappedBy="elementGroup", fetch=FetchType.EAGER )
	@OrderBy("name asc")
	private List<Element> element;
}
{noformat}


was (Author: fbjon):
It seems this bug can indeed show up even if all applicable fields have @OrderBy-annotations. In the following abbreviated example, trying to update (merge) an existing Element-entity after starting up the system results in this same NPE. However, persisting an ElementGroup causes the relevant internal metadata fields to be populated (i.e. {{_orderDec}}, and everything works after that. There is no workaround that I can see short of using reflection to mess with the OpenJPA internals.

 
{noformat}
@Entity
public class Element {

	@OneToMany(cascade=CascadeType.PERSIST, mappedBy="element", fetch=FetchType.LAZY )
	@OrderBy("order asc")
	private List<PageElement> pageElement;
	
	@Column(name = "NAME", length=255)
	private String name;
	
	@ManyToOne( fetch=FetchType.EAGER )
	private ElementGroup elementGroup;
}

@Entity
public class PageElement {

	@Column( name="ORDER" )
	private Long order;

	@ManyToOne( fetch=FetchType.EAGER )
	private Element element;
}

@Entity
public class ElementGroup {

	@OneToMany(cascade=CascadeType.ALL, mappedBy="elementGroup", fetch=FetchType.EAGER )
	@OrderBy("name asc")
	private List<Element> element;
}
{noformat}

> NPE was thrown out when a @OrderBy modified column is being persisted.
> ----------------------------------------------------------------------
>
>                 Key: OPENJPA-2429
>                 URL: https://issues.apache.org/jira/browse/OPENJPA-2429
>             Project: OpenJPA
>          Issue Type: Bug
>          Components: datacache
>    Affects Versions: 2.2.1
>         Environment: Windows 7
> WebSphere 8.5
>            Reporter: Kymair Wu
>            Priority: Major
>         Attachments: OpenJPA-2429.diff
>
>
> Following NPE was thrown out when a @OrderBy modified column is being persisted.
> {quote}
> Caused by: java.lang.NullPointerException
>         at org.apache.openjpa.datacache.DataCachePCDataImpl.clearInverseRelationCache(DataCachePCDataImpl.java:179)
>         at org.apache.openjpa.datacache.DataCachePCDataImpl.storeField(DataCachePCDataImpl.java:159)
> {quote}
> I notice that getOrderDeclaration() of FieldMetaData will return null when both _orders and _orderDec are null, which cause the NPE.
> The only place _orders will be set after class initialization seems to be getOrders()? But getOrders() is not involved for all the FieldMetaData of "fields[i].getInverseMetaDatas()"
> I'm not sure whether this is a OpenJPA issue but whether this NPE should be handled internally? 
> Google returns a potential case but no more information found. See https://issues.apache.org/jira/browse/OPENJPA-2096?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel and http://mail-archives.apache.org/mod_mbox/openjpa-users/201006.mbox/%3C4C1BE781.9000406@cyberspaceroad.com%3E
> Thanks!



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