Serialize XML from a dynamic array

The XMLList and XMLName attributes can be used to serialize dynamic arrays to XML and vice versa.

These attributes have distinct uses depending on the output you want.

The XMLList attribute is used especially to produce a list of the same elements from an array, without a surrounding tag. This output on its own is not valid XML because there is no parent node. For valid XML output, the attribute must be used inside another variable, such as a record. Compare Example 1: List of the same elements and Example 3: List inside a record.

It is useful to use XMLList specifically to map a one dimensional array to an XML schema element that has more than one occurrence, inside another XML element.

An array (without XMLList ), on the other hand, always produces a surrounding tag and thus a valid XML document. See Example 2: Array of the same elements and Example 4: Array inside a record.

The XMLName attribute's function is to provide a name for XML elements. If you do not use the XMLName attribute, the tags used in the XML output are the names of the 4GL variables. Or if there are no variables, they are named "<element>".

Tip: The variables with these attributes you use to output to XML, may also be used to load an XML document into DYNAMIC ARRAY.

Example 1: List of the same elements

This example shows how an array defined with XMLList outputs a list of the same elements. Typically, this array is defined inside another variable (see Example 3: List inside a record), because the resulting XML is not valid otherwise. The XMLName attribute is set to name the element.

DEFINE a RECORD
    list DYNAMIC ARRAY ATTRIBUTES(XMLList) OF STRING ATTRIBUTE(XMLName="MyElt")
END RECORD

This would produce an XML output like this:

<MyElt>One</MyElt><MyElt>Two</MyElt>

When viewed in an XML viewer, it would display as shown.

<MyElt>One</MyElt>
<MyElt>Two</MyElt>

Example 2: Array of the same elements

In this example an array is defined without XMLList. This produces output that is a valid XML document with an array of the same elements, and a surrounding tag. The XMLName attribute tags both the array and the elements.

DEFINE arr DYNAMIC ARRAY ATTRIBUTE(XMLName="SurroundingTag") OF STRING ATTRIBUTE(XMLName="MyElt")

The XML output may look like this:

<SurroundingTag><MyElt>One</MyElt><MyElt>Two</MyElt></SurroundingTag>

When viewed in an XML viewer, it would display as shown.

<SurroundingTag>
   <MyElt>One</MyElt>
   <MyElt>Two</MyElt>
</SurroundingTag>

Example 3: List inside a record

The XMLList must be defined inside another variable, such as a record, in order to produce output that is a valid XML document. Several lists may be included in the record.

DEFINE myVar1 RECORD ATTRIBUTES(XMLName="Root")
   val1  INTEGER ATTRIBUTES(XMLName="Val1"),
   list  DYNAMIC ARRAY ATTRIBUTE(XMLList) OF STRING ATTRIBUTES(XMLName="MyElt"),
   val2  FLOAT   ATTRIBUTES(XMLName="Val2")
END RECORD

This would produce XML output like this:

<Root><Val1>148</Val1><MyElt>hello</MyElt><MyElt>there</MyElt><Val2>0.58</Val2></Root>

When viewed in an XML viewer, it would display as shown.

<Root>
  <Val1>148</Val1>
  <MyElt>hello</MyElt>
  <MyElt>there</MyElt>
  <Val2>0.58</Val2>
</Root>

Example 4: Array inside a record

This example shows that the array is output inside a surrounding tag inside the record.

DEFINE myVar2 RECORD ATTRIBUTES(XMLName="Root")
   val1  INTEGER ATTRIBUTES(XMLName="Val1"),
   arr  DYNAMIC ARRAY ATTRIBUTES(XMLName="Sample") OF STRING ATTRIBUTES(XMLName="MyElt"),
   val2  FLOAT   ATTRIBUTES(XMLName="Val2")
END RECORD

This would produce XML output like this:

<Root><Val1>148</Val1><Sample><MyElt>hello</MyElt><MyElt>there</MyElt></Sample><Val2>0.58</Val2></Root>

When viewed in an XML viewer, it would display as shown.

<Root>
   <Val1>148</Val1>
   <Sample>
	<MyElt>hello</MyElt>
	<MyElt>there</MyElt>
   </Sample>
   <Val2>0.58</Val2>
</Root>