org.apache.tapestry.valid
Interface IValidationDelegate

All Known Implementing Classes:

ValidationDelegate

public interface IValidationDelegate

Interface used to track validation errors in forms and IFormComponents (including AbstractTextFieldand its subclasses).

In addition, controls how fields that are in error are presented (they can be marked in various ways by the delegate; the default implementation adds two red asterisks to the right of the field).

The interface is designed so that a single instance can be shared with many instances of IFormComponent.

Starting with release 1.0.8, this interface was extensively revised (in a non-backwards compatible way) to move the tracking of errors and invalid values (during a request cycle) to the delegate. It has evolved from a largely stateless conduit for error messages into a very stateful tracker of field state.

Starting with release 1.0.9, this interface was again reworked, to allow tracking of errors in form components, and to allow unassociated (with any field) errors to be tracked.

Fields vs. Form Components
For most simple forms, these terms are pretty much synonymous. Your form will render normally, and each form component will render only once. Some of your form components will be ValidFieldcomponents and handle most of their validation internally (with the help of IValidatorobjects). In addition, your form listener may do additional validation and notify the validation delegate of additional errors, some of which are associated with a particular field, some of which are unassociated with any particular field.

But what happens if you use a Foreachor ListEditinside your form? Some of your components will render multiple times. In this case you will have multiple fields. Each field will have a unique field name (you can see this in the generated HTML). It is this field name that the delegate keys off of, which means that some fields generated by a component may have errors and some may not, it all works fine (with one exception).

The Exception
The problem is that a component doesn't know its field name until its render() method is invoked (at which point, it allocates a unique field name from the IForm.getElementId(org.apache.tapestry.form.IFormComponent). This is not a problem for the field or its IValidator, but screws things up for the FieldLabel.

Typically, the label is rendered before the corresponding form component. Form components leave their last assigned field name in their name property. So if the form component is in any kind of loop, the FieldLabelwill key its name, display name and error status off of its last renderred value. So the moral of the story is don't use FieldLabelin this situation.

Author:

Howard Lewis Ship

Method Summary

void	clear() Clears all tracking information.
void	clearErrors() Clears all errors, but maintains user input.
IFieldTracking	getCurrentFieldTracking() Returns the IFieldTrackingfor the current component, if any.
String	getFieldInputValue() Returns the string submitted by the client as the value for the current field.
List	getFieldTracking() Returns a Listof IFieldTracking, in default order (the order in which fields are renderred).
boolean	getHasErrors() Returns true if any form component has errors.
boolean	isInError() Returns true if the current component is in error (that is, had bad input submitted by the end user).
void	record(IRender errorRenderer, ValidationConstraint constraint) Records an error in the current component, or an unassociated error.
void	record(String message, ValidationConstraint constraint) Records an error in the current field, or an unassociated error if there is no current field.
void	record(ValidatorException ex) The error notification method, invoked during the rewind phase (that is, while HTTP parameters are being extracted from the request and assigned to various object properties).
void	recordFieldInputValue(String input) Records the user's input for the current form component.
void	reset() Resets any tracking information for the current field.
void	setFormComponent(IFormComponent component) Invoked before other methods to configure the delegate for the given form component.
void	writeAttributes(IMarkupWriter writer, IRequestCycle cycle, IFormComponent component, IValidator validator) Invoked just before the <input> element is closed.
void	writeLabelPrefix(IFormComponent component, IMarkupWriter writer, IRequestCycle cycle) Invoked by a FieldLabeljust before writing the name of the form component.
void	writeLabelSuffix(IFormComponent component, IMarkupWriter writer, IRequestCycle cycle) Invoked by a FieldLabeljust after writing the name of the form component.
void	writePrefix(IMarkupWriter writer, IRequestCycle cycle, IFormComponent component, IValidator validator) Invoked before the field is rendered.
void	writeSuffix(IMarkupWriter writer, IRequestCycle cycle, IFormComponent component, IValidator validator) Invoked after the form component is rendered, so that the delegate may decorate the form component (if it is in error).

Method Detail

setFormComponent

void setFormComponent(IFormComponent component)

Invoked before other methods to configure the delegate for the given form component. Sets the current field based on the nameof the form component (which is almost always a ValidField).

The caller should invoke this with a parameter of null to record unassociated global errors (errors not associated with any particular field).

Since:

1.0.8

isInError

boolean isInError()

Returns true if the current component is in error (that is, had bad input submitted by the end user).

Since:

1.0.8

getFieldInputValue

String getFieldInputValue()

Returns the string submitted by the client as the value for the current field.

Since:

1.0.8

getFieldTracking

List getFieldTracking()

Returns a Listof IFieldTracking, in default order (the order in which fields are renderred). A caller should not change the values (the List is immutable). May return null if no fields are in error.

Since:

1.0.8

reset

void reset()

Resets any tracking information for the current field. This will clear the field's inError flag, and set its error message and invalid input value to null.

Since:

1.0.8

clear

void clear()

Clears all tracking information.

Since:

1.0.10

clearErrors

void clearErrors()

Clears all errors, but maintains user input. This is useful when a form has been submitted for a semantic other than "process this data". A common example of this is a dependent drop down list; selecting an option in one drop down list forces a submit to repopulate the options in a second, dependent drop down list.

In these cases, the user input provided in the request is maintained, but any errors should be cleared out (to prevent unwanted error messages and decorations).

Since:

3.0.1

recordFieldInputValue

void recordFieldInputValue(String input)

Records the user's input for the current form component. Input should be recorded even if there isn't an explicit error, since later form-wide validations may discover an error in the field.

Since:

3.0

record

void record(ValidatorException ex)

The error notification method, invoked during the rewind phase (that is, while HTTP parameters are being extracted from the request and assigned to various object properties).

Typically, the delegate simply invokes record(String, ValidationConstraint)or record(IRender, ValidationConstraint), but special delegates may override this behavior to provide (in some cases) different error messages or more complicated error renderers.

record

void record(String message,
            ValidationConstraint constraint)

Records an error in the current field, or an unassociated error if there is no current field.

Parameters:

message - message to display (@see RenderString}

constraint - the constraint that was violated, or null if not known

Since:

1.0.9

record

void record(IRender errorRenderer,
            ValidationConstraint constraint)

Records an error in the current component, or an unassociated error. The maximum flexibility recorder.

Parameters:

errorRenderer - object that will render the error message (@see RenderString}. The object should implement a reasonable toString() as well, to allow the error message to be rendered using an Insert component, or used where full markup is not allowed.

constraint - the constraint that was violated, or null if not known

writePrefix

void writePrefix(IMarkupWriter writer,
                 IRequestCycle cycle,
                 IFormComponent component,
                 IValidator validator)

Invoked before the field is rendered. If the field is in error, the delegate may decorate the field in some way (to highlight its error state).

writeAttributes

void writeAttributes(IMarkupWriter writer,
                     IRequestCycle cycle,
                     IFormComponent component,
                     IValidator validator)

Invoked just before the <input> element is closed. The delegate can write additional attributes. This is often used to set the CSS class of the field so that it can be displayed differently, if in error (or required).

Since:

1.0.5

writeSuffix

void writeSuffix(IMarkupWriter writer,
                 IRequestCycle cycle,
                 IFormComponent component,
                 IValidator validator)

Invoked after the form component is rendered, so that the delegate may decorate the form component (if it is in error).

writeLabelPrefix

void writeLabelPrefix(IFormComponent component,
                      IMarkupWriter writer,
                      IRequestCycle cycle)

Invoked by a FieldLabeljust before writing the name of the form component.

writeLabelSuffix

void writeLabelSuffix(IFormComponent component,
                      IMarkupWriter writer,
                      IRequestCycle cycle)

Invoked by a FieldLabeljust after writing the name of the form component.

getHasErrors

boolean getHasErrors()

Returns true if any form component has errors.

getCurrentFieldTracking

IFieldTracking getCurrentFieldTracking()

Returns the IFieldTrackingfor the current component, if any. Useful when displaying error messages for individual fields.

Since:

3.0.2