XMLElementNillable

The XMLElementNillable attribute specifies that all members of a RECORD have to be serialized as xsi:nil="true" when NULL. This has the same effect as defining each individual element with the XMLNillable attribute.

The XMLElementNillable attribute can only be set on records defined by TYPE or DEFINE.

The XMLElementNillable attribute supports the record defined with LIKE clause to use the table definition from a database schema:

DEFINE rec RECORD ATTRIBUTE(XMLElementNillable) LIKE customer.*

If columns in the database table are allowed to be null, you must add the XMLElementNillable attribute to the record definition.

The XMLElementNillable attribute is not inherited by sub records.

Basic example

DEFINE rec RECORD ATTRIBUTE(XMLElementNillable)
  val1 STRING,
  val2 STRING
END RECORD

LET rec.val1 = "Hello"
LET rec.val2 = NULL

In the resulting XML document, "val2" is serialized with the xsi:nil="true":

<rec>
  <val1>Hello</val1>
  <val2 xsi:nil="true"/>
</rec>

Example using a sub record

Since XMLElementNillable attribute is not inherited by sub records, you must set it on each sub-record if needed:

DEFINE rec RECORD ATTRIBUTE(XMLElementNillable)
  val1 STRING,
  val2 STRING,
  subrec RECORD
    val3 STRING
  END RECORD
END RECORD

In the resulting XML document, for instance, only "val1" and "val2" are serialized as xsi:nil="true" when NULL, but "val3" is not.

To have "val3" serialized as xsi:nil="true" when NULL, define:

DEFINE rec RECORD ATTRIBUTE(XMLElementNillable)
  val1 STRING,
  val2 STRING,
  subrec RECORD ATTRIBUTE(XMLElementNillable)
    val3 STRING
  END RECORD
END RECORD

Examples with XMLNillable and XMLOptional

The XMLElementNillable attribute does not allow values, so you cannot write XMLElementNillable="preferred" as you do for XMLNillable.

If XMLOptional is set on a record member, XMLElementNillable is not taken into account.

If you need XMLNillable to take precedence over XMLOptional, you must then specify XMLNillable="preferred" on the record member.

In the following sample, if "val2" is NULL, it will serialize to the tag not being present because XMLOptional hides XMLElementNillable. On the other hand, if "val3" is NULL, it will be serialized as xsi:nil="true", because the record member is defined with XMLOptional and XMLNillable (preferred):

DEFINE rec RECORD ATTRIBUTE(XMLElementNillable)
  val1 STRING,
  val2 STRING ATTRIBUTE(XMLOptional),
  val3 STRING ATTRIBUTE(XMLOptional,XMLNillable="preferred")
END RECORD

LET rec.val1 = "Hello"
LET rec.val2 = NULL
LET rec.val3 = NULL

Will be serialized as:

<rec>
  <val1>Hello</val1>
  <val3 xsi:nil="true"/>
</rec>