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 IField).

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 is 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 (not just IFields}, and to allow unassociated (with any field) errors to be tracked.

Fields vs. IField 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 by ValidField components and handle most of their validation internally (with the help of IValidator objects). 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 Foreach or ListEdit inside 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 org.apache.tapestry.IForm#getElementId(IComponent). 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 FieldLabel will key its name, display name and error status off of its last renderred value. So the moral of the story is don't use FieldLabel in this situation.

Version:
$Id: IValidationDelegate.java,v 1.3 2003/04/17 21:33:58 hlship Exp $
Author:
Howard Lewis Ship

Method Summary
 void clear()
          Clears all tracking information.
 String getFieldInputValue()
          Returns the string submitted by the client as the value for the current field.
 List getFieldTracking()
          Returns a List of 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 FieldLabel just before writing the name of the form component.
 void writeLabelSuffix(IFormComponent component, IMarkupWriter writer, IRequestCycle cycle)
          Invoked by a FieldLabel just 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

public void setFormComponent(IFormComponent component)
Invoked before other methods to configure the delegate for the given form component. Sets the current field based on the name of 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

public 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

public String getFieldInputValue()
Returns the string submitted by the client as the value for the current field.
Since:
1.0.8

getFieldTracking

public List getFieldTracking()
Returns a List of 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

public 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

public void clear()
Clears all tracking information.
Since:
1.0.10

recordFieldInputValue

public 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

public 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

public 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

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

writePrefix

public 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

public 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

public 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

public void writeLabelPrefix(IFormComponent component,
                             IMarkupWriter writer,
                             IRequestCycle cycle)
Invoked by a FieldLabel just before writing the name of the form component.

writeLabelSuffix

public void writeLabelSuffix(IFormComponent component,
                             IMarkupWriter writer,
                             IRequestCycle cycle)
Invoked by a FieldLabel just after writing the name of the form component.

getHasErrors

public boolean getHasErrors()
Returns true if any form component has errors.