See also Form Builder Validation.
Orbeon Forms validates XForms instances following XForms 1.1 and adds some extensions to facilitate validation.
There are two main methods for validating data in XForms:
with an imported XML Schema
Using a bind allows you to create precise error messages to the user based on the type of data entry error.
Orbeon Forms performs validation of a node in the following order:
data type validation
XML Schema validation (lax/strict/none on model instances)
are checked only if the control's data type is valid
[SINCE Orbeon Forms 4.3]
XForms allows a single
constraint attribute on the
xf:bind element. Orbeon Forms extends this to support any number of nested
xf:constraint elements, each specifying a single validation:
<xf:bind ref="." id="input-bind"><xf:constraintid="length-constraint"level="error"value="string-length() gt 1"/><xf:constraintid="uppercase-constraint"level="warning"value="for $first in substring(., 1, 1) return upper-case($first) = $first"/></xf:bind>
Each constraint applies to the enclosing
level: optional, specifies an alert level (defaults to
constraint: XPath expression specifying the constraint
id attribute is optional and useful to attach alerts.
Constraints combine with a logical "and" for a given level. For example, if the error level is used (the default), the value is valid only if all constraints evaluate to
If there is a single error constraint, the following binds are equivalent:
<xf:bind ref="." id="input-bind" constraint="string-length() gt 1"/><xf:bind ref="." id="input-bind"><xf:constraint level="error" value="string-length() gt 1"/></xf:bind>
[SINCE Orbeon Forms 4.3]
Orbeon Forms supports the following validation levels:
error (which corresponds to XForms's valid/invalid)
The default validation level is error.
The warning and info levels allow checking validation conditions that are weaker than errors.
Levels are hierarchical. If a control is valid, it can have a warning level. This is the case if there is at least one failed warning constraint.
If a control doesn't have a warning level, it can have an info level. This is the case if there is at least one failed info constraint.
A warning or info level does not make the control value invalid and it is still possible to submit form data.
NOTE: As of Orbeon Forms 4.3, it is only possible to associate a warning or info validation level to a constraint specified with
xf:constraint/@value. It is not possible to associate these levels to the required or data type validations: they always use the error level.
[SINCE Orbeon Forms 4.9]
required attributes, you can use
xf:required elements nested within
This allows assigning a specific identifier to a validation with the
id attribute, so that
xf:alert can refer to those with the
<xf:bind id="control-1-bind" name="control-1" ref="control-1"><xf:required value="true()" id="validation-3-validation"/><xf:type id="validation-4-validation">xs:decimal</xf:type><xf:constraint value=". ge 10" id="validation-5-validation"/><xf:constraint value=". ge 20" id="validation-6-validation" level="warning"/></xf:bind><fr:number bind="control-1-bind"><xf:alert ref="$form-resources/control-1/alert" validation="validation-3-validation"/><xf:alert ref="$form-resources/control-1/alert" validation="validation-4-validation"/><xf:alert ref="$form-resources/control-1/alert" validation="validation-5-validation"/><xf:alert ref="$form-resources/control-1/alert" validation="validation-6-validation"/><xf:alert ref="$fr-resources/detail/labels/alert"/></fr:number>
This allows having distinct alerts for indicating:
that the value is required
that the value must be of the given datatype
that the value must satisfy constraints expressed in XPath
LIMITATION: As of Orbeon Forms 4.9, only the first
type and the first
required attribute or element associated with an
xf:bind element are taken into account. On the other hand, all
constraint elements are handled.
[SINCE Orbeon Forms 4.3]
A control can have more than one
xf:alert element. By default, an
xf:alert is considered the default alert for the control and is active for all validation levels and constraints:
level attribute is specified, the alert is active for the given levels:
<xf:alert level="warning info">
validation attribute is specified, the alert is active only for the given validations:
<xf:alert validation="c1 c2">
In this example,
c2 refer to
id attributes on
xf:constraint elements. Only
xf:constraint elements associated with a bind pointing to the node to which the control is bound are considered.
validation attributes are equivalent to no attributes.
validation attributes are specified,
level is ignored:
<xf:alert level="error" validation="c1 c2">
More than one alert can be active at the same time, following a hierarchy:
If the control doesn't have a validation level, no alert is active.
If there is a level:
If there is a failed required validation, the default alert is active.
Otherwise, if there is a failed data type validation, the default alert is active.
Otherwise, if there are alerts that match specific failed constraints, those alerts and no others are active.
Otherwise, if there are alerts that match the specific level, those alerts and no others are active.
Otherwise, if present, the default alert is active.
Otherwise, no alert is active.
NOTE: This is the behavior as of Orbeon Forms 4.6.2 and newer, see #1830. Prior to that, a failed required validation was at the same level as other failed validations. The 4.6.2 behavior makes it so that the required validation has priority over other error validations.
<xf:bind ref="." id="input-bind"><xf:constraintid="length-constraint"level="error"value="string-length() gt 1"/><xf:constraintid="uppercase-constraint"level="warning"value="for $first in substring(., 1, 1) return upper-case($first) = $first"/></xf:bind><xf:input id="my-input" ref="."><xf:alert id="alert-1">All levels</xf:alert><xf:alert id="alert-2" level="error">Error level</xf:alert><xf:alert id="alert-3" level="warning">Warning level</xf:alert><xf:alert id="alert-4" level="error warning">Error and warning level</xf:alert><xf:alert id="alert-5" validation="length-constraint">Length constraint</xf:alert><xf:alert id="alert-6" validation="uppercase-constraint">Uppercase constraint</xf:alert><xf:alert id="alert-7" validation="length-constraint uppercase-constraint">Both constraints</xf:alert></xf:input>
[SINCE Orbeon Forms 2016.3]
Single-node controls support the
xxf:validation-mode attribute, with the following values:
incremental: upon refresh, update the control's validity information (default)
explicit: upon refresh, don't update the control's validity information
When used on grouping controls, descendant controls inherit the value.
explicit mode, the following action allows explicitly updating the validity information on a control or subtree of controls:
makes sure the UI is up to date
updates the validity of the selected controls which have
xxf:validation-mode set to
marks the UI for a subsequent refresh
control: space-separated list of controls to update
recurse: when set to
true, check all descendant controls of the specified controls as well
Orbeon Forms supports extensions events dispatched to an instance when it becomes valid or invalid:
These events are dispatched just after
xforms-revalidate completes on a given model to all instances that change their validation state (from valid to invalid or from invalid to valid):
If the instance is newly valid,
xxforms-valid is dispatched
If the instance is newly invalid,
xxforms-invalid is dispatched
Before the initial validation of a model, instances are assumed to be in the valid state.
These events can be used, for example, to toggle the appearance of icons indicating that a form is valid or invalid:
<xf:instance id="my-instance">...</xf:instance><xf:action ev:event="xxforms-invalid" ev:observer="my-instance"><xf:toggle case="invalid-form-case"/></xf:action><xf:action ev:event="xxforms-valid" ev:observer="my-instance"><xf:toggle case="valid-form-case"/></xf:action>
These events are dispatched just before
xforms-revalidate completes, to all instances of the model being revalidated. For a given instance, either
xxforms-invalid is dispatched for a given revalidation.
[SINCE Orbeon Forms 4.3]
This event is dispatched to a control whenever the list of failed constraints associated with the control's bound node change.
level: the control's current validation level ("error", "warning", "info", or the empty sequence)
constraints: ids of all current failed constraints
errors: ids of current failed error constraints
warnings: ids of current failed warning constraints (empty if current level is "error")
infos: ids of current failed info constraints (empty if current level is "warning" or "error")
added-errors: ids of current errors added since the last refresh
removed-errors: ids of current errors removed since the last refresh
added-warnings: ids of current warnings added since the last refresh
removed-warnings: ids of current warnings removed since the last refresh
added-infos: ids of current infos added since the last refresh
removed-infos: ids of current infos removed since the last refresh
NOTE: A bug until Orbeon Forms 2017.2 caused the event to be dispatched to all controls during the first refresh..
xxf:valid() returns the validity of a instance data node or of a subtree of instance data.
xxf:invalid-binds() allows you to determine which bind caused node invalidity.
This types checks that the value is well-formed XML:
<xf:bind ref="my-xml" type="xxf:xml"/>
Note that this checks the string value of the node, which means that the node must contain escaped XML.
This types checks that the value is well-formed XPath 2.0. Any variable used by the expression is assumed to be in scope:
<xf:bind ref="my-xpath" type="xxf:xpath2"/>
NOTE: In both these cases, Orbeon Forms checks for the required MIP: if it evaluates to
false() and the value is the empty string, then the instance data node is considered valid. This is contrary to XForms 1.1.
When an XML Schema is provided, Orbeon Forms supports controlling whether a particular instance is validated in the following modes:
not validated at all ("skip" mode)
Orbeon Forms implements a "lax" validation mode by default, where only elements that have definitions in the imported schemas are validated. Other elements are not considered for validation. This is in line with XML Schema and XSLT 2.0 lax validation modes, and with the default validation mode as specified in XForms 1.1
In addition, the author can specify the validation mode directly on each instance with the extension attribute
xxf:validation, which takes values:
lax (the default)
strict (the root element has to have a definition in the schema and must be valid)
skip (no validation at all for that instance)
<xf:model schema="my-schema.xsd"><xf:instance id="my-form" xxf:validation="strict"><my-form> ... </my-form></xf:instance><xf:instance id="items" xxf:validation="skip"><items> ... </items></xf:instance></xf:model>
Nodes validated through an XML Schema receive data type annotations, which means that if an element or attribute is validated against
xs:date in a schema, an XForms control bound to that node will display a date picker.