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Home » Eclipse Projects » EclipseLink » JPQL LEFT JOIN FETCH Results in NPE when DescriptorCustomizer in Place
JPQL LEFT JOIN FETCH Results in NPE when DescriptorCustomizer in Place [message #1344282] Fri, 09 May 2014 17:59
Scott Dudley is currently offline Scott DudleyFriend
Messages: 21
Registered: October 2012
Junior Member
I have a unidirectional one-to-many mapping between the following two entities:

@Entity
@Table(name="INVC_CNTRL")
public class InvoiceControl implements Serializable {

    @Id
    @Column(name="INVC_CNTRL_ID")
    private Long invoiceControlId = null;
...
    @OneToMany(fetch = FetchType.LAZY)
    private List<UserDefined> userDefineds;

@Entity
@Table(name="USER_DEFINED")
public class UserDefined implements Serializable {
...
    @Column(name="USER_DEFINED_TABLE")
    private java.lang.String userDefinedTable;

    @Column(name="USER_DEFINED_FK")
    private long userDefinedForeignKey;


I wrote the following DescriptorCustomizer to address a constant JoinColumn value:

        ManyToManyMapping mapping = (ManyToManyMapping) descriptor.getMappingForAttributeName("userDefineds");
        if (null != mapping) {
            String tableName = descriptor.getTableName();
            String primaryKey = descriptor.getPrimaryKeyFields().get(0).getName();
            ExpressionBuilder builder = new ExpressionBuilder(mapping.getReferenceClass());
            mapping.setSelectionCriteria(builder.getField("USER_DEFINED_FK").equal(builder.getParameter(primaryKey))
                .and(builder.getField("USER_DEFINED_TABLE").equal(tableName)));
        }


This works as expected with JPQL "select a from InvoiceControl a join fetch a.userDefineds" but when I change the "join fetch" to "left join fetch", I get the following NPE:

Caused by: java.lang.NullPointerException
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.appendFromClauseForOuterJoin(SQLSelectStatement.java:403)
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.appendFromClauseToWriter(SQLSelectStatement.java:521)
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.printSQL(SQLSelectStatement.java:1679)
	at org.eclipse.persistence.internal.databaseaccess.DatabasePlatform.printSQLSelectStatement(DatabasePlatform.java:3178)
	at org.eclipse.persistence.platform.database.OraclePlatform.printSQLSelectStatement(OraclePlatform.java:932)
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.buildCall(SQLSelectStatement.java:782)
	at org.eclipse.persistence.internal.expressions.SQLSelectStatement.buildCall(SQLSelectStatement.java:792)
	at org.eclipse.persistence.descriptors.ClassDescriptor.buildCallFromStatement(ClassDescriptor.java:813)
	at org.eclipse.persistence.internal.queries.StatementQueryMechanism.setCallFromStatement(StatementQueryMechanism.java:390)
	at org.eclipse.persistence.internal.queries.StatementQueryMechanism.prepareSelectAllRows(StatementQueryMechanism.java:315)
	at org.eclipse.persistence.internal.queries.ExpressionQueryMechanism.prepareSelectAllRows(ExpressionQueryMechanism.java:1721)
	at org.eclipse.persistence.queries.ReadAllQuery.prepareSelectAllRows(ReadAllQuery.java:813)
	at org.eclipse.persistence.queries.ReadAllQuery.prepare(ReadAllQuery.java:744)
	at org.eclipse.persistence.queries.DatabaseQuery.checkPrepare(DatabaseQuery.java:661)
	... 8 more


Inspecting the 2.5.1 source, this suggests relationAlias is null.

I've tried a number of things to no avail. If I disable the DescriptorCustomizor and instead add a @JoinColumn on the OneToMany defining half of the join, it works. Of course the result is incorrect because it's failing to discriminate by the table name.

Is this a bug or am I making another JPA noob mistake?

Thanks.
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