Handling Null, Empty, and Missing Values - Documentation for Ar System 22.1
This Topic Discusses the Rules for Handling Null, Empty, and Missing Values. Elements and Attributes Mapped to fieldsThe Rules for Mapping Xml Elements and...
This topic discusses the rules for handling null, empty, and missing values.
Elements and attributes mapped to fields
The rules for mapping XML elements and attributes to fields can be divided into four groups.
- Incoming XML elements
- Incoming XML attributes
- Outgoing XML elements
- Outgoing XML attributes
AR System has two sources for incoming XML:
- The request for published web service published through AR System
- A response from an external web service that AR System is consuming
Similarly, there are two sources for outgoing XML:
- The response from a web service published through AR System
- The request to an external web service that AR System is consuming
In these tables it is assumed that "name" is an XML element or attribute that is missing, empty, or nulled, and is mapped to a AR System field called Name. The column headers are the design-time properties. For example, "name" is defined with minOccurs=0 and nillable=false. The row headers are run-time representations. For example, in the incoming XML packet "name" appears as <name></name>. The table specifies how AR System sets the XML element or attribute to or from the AR System field.
Tip
To render a null field, create an empty element with xsi:nil=true as an attribute. This is preferable to omitting the element in the request document, or creating an empty element with the nillable attribute set to false.
Must Read
Incoming XML elements mapped to fields
minOccurs=0 and nillable=false | minOccurs=0 and nillable=true | minOccurs=1 and nillable=false | minOccurs=1 and nillable=true | |
Missing <name> | Name is not modified, or it is set to AR default. (1) | Name is not modified, or it is set to AR default. (1) | Invalid XML (2) | Invalid XM. (2) |
<name></name> OR <name/> | Name=$NULL$ or xsd default (3) | Name=$NULL$ or xsd default (3) | Name=$NULL$ or xsd default (3) | Name=$NULL$ or xsd default (3) |
<name xsi:nil="true></name> OR <name xsi:nil="true"/> | Invalid XML. (5) | Name=$NULL$ (4) | Invalid XML (5) | Name=$NULL$ (4) |
- When an XML element is missing, AR System treats it the same way as a missing field. Therefore, in a create operation, the field to which the XML element is mapped assumes the AR System default value (or NULL if there is no default). In a set operation and in consumption, the field remains unchanged.
- When an XML element is missing, in spite of minOccurs=1, it is invalid XML. The client should not send such an XML packet, but if it does, AR System displays an error message.
- When the XML element has empty content, AR System first tries to use the xsd default if it exists. (There are two different defaults—the AR System default value and the xsd default value. For empty contents, AR System always uses the default xsd value.) Otherwise, it sets the field to NULL.
- When the XML element has xsi:nil=true, AR System sets the field to NULL and disregards the defaults.
- When the XML element has xsi:nil=true but is not defined with nillable=true, it is invalid XML. Clients should not send such an XML packet. Also, AR System sets this field to NULL, disregarding the defaults.
- To an XML element to be returned in a Web Service output, AR Server adds the xsi:nil attribute only if the XML element has a NULL value, is defined to allow NULL values (nillable=true), and there is no default value assigned to it.
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