ValueChangeValidator (OmniFaces 4.0 API)

java.lang.Object
- org.omnifaces.validator.ValueChangeValidator<T>

All Implemented Interfaces:

Validator<T>, EventListener
```
public abstract class ValueChangeValidator<T>
extends Object
implements Validator<T>
```
By default, Faces validators run on every request, regardless of whether the submitted value has changed or not. In case of validation against the DB on complex objects which are already stored in the model in a broader scope, such as the view scope, this may result in unnecessarily expensive service/DAO calls. In such case, you'd like to perform the expensive service/DAO call only when the submitted value is really changed as compared to the model value.
This validator offers you a template to do it transparently. To use it, just change your validators from:
```
 public class YourValidator implements Validator<YourEntity> {

     public void validate(FacesContext context, UIComponent component, YourEntity submittedValue) {
         // ...
     }

 }
 
```
to
```
 public class YourValidator extends ValueChangeValidator<YourEntity> {

     public void validateChangedObject(FacesContext context, UIComponent component, YourEntity submittedValue) {
         // ...
     }

 }
 
```
So, essentially, just replace implements Validator by extends ValueChangeValidator and rename the method from validate to validateChangedObject.
Since:

1.7

Author:

Juliano, Bauke Scholtz

Field Summary
- Fields inherited from interface jakarta.faces.validator.Validator
  NOT_IN_RANGE_MESSAGE_ID

Constructor Summary

Constructors
Constructor Description

ValueChangeValidator()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`validate(FacesContext context, UIComponent component, T submittedValue)`	If the component is an instance of `EditableValueHolder` and its old object value is equal to the submitted value, then return immediately from the method and don't perform any validation.
`abstract void`	`validateChangedObject(FacesContext context, UIComponent component, T submittedValue)`	Use this method instead of `validate(FacesContext, UIComponent, Object)` if you intend to perform the validation only when the submitted value is really changed as compared to the model value.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ValueChangeValidator
```
public ValueChangeValidator()
```
- Method Detail
  - validate
```
public void validate(FacesContext context,
                     UIComponent component,
                     T submittedValue)
```
    If the component is an instance of EditableValueHolder and its old object value is equal to the submitted value, then return immediately from the method and don't perform any validation. Otherwise, invoke validateChangedObject(FacesContext, UIComponent, Object) which may in turn do the necessary possibly expensive DAO operations.
    
    Specified by:
    
    validate in interface Validator<T>
  - validateChangedObject
```
public abstract void validateChangedObject(FacesContext context,
                                           UIComponent component,
                                           T submittedValue)
```
    Use this method instead of validate(FacesContext, UIComponent, Object) if you intend to perform the validation only when the submitted value is really changed as compared to the model value.
    
    Parameters:
    
    context - The involved faces context.
    
    component - The involved UI component.
    
    submittedValue - The submitted value.