[Tapestry Wiki] Update of "CreatingCustomValidators" by SebastianHennebrueder

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The following page has been changed by SebastianHennebrueder:
http://wiki.apache.org/tapestry/CreatingCustomValidators

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  = Creating a custom validator =
- applies to: Tapestry 4.0
+ Explains how to write and integrate custom validators for Tapestry 4 and 5
+ 
+ == Tapestry 5.0 ==
+ Author: Sebastian Hennebrueder, Date: August 2009
+ There are 3 steps:
+  1. Create a validator
+  1. Create a resource file for validation messages
+  1. Register both in your application
+ 
+ === Create a validator ===
+ The following validator check if the value is not 'foo' because foo is really a bad value. It
+ expects a String and no configuration parameter. The {{{MinLength}}} validator uses a configuration parameter to define the minimum length.
+ The validation error messages has the key {{{foo-not-allowed}}}. You might check the source code of the existing validators for further inspiration.
+ {{{
+ import org.apache.tapestry5.validator.AbstractValidator;
+ // ... some more imports here
+ public class FooValidator extends AbstractValidator<Void, String> {
+ 	public FooValidator() {
+ 		super(null, String.class, "foo-not-allowed");
+ 	}
+ 
+ 	public void validate(Field field, Void constraintValue, MessageFormatter formatter, String value)
+ 			throws ValidationException {
+ 		if ("foo". equals(value))
+ 			throw new ValidationException(buildMessage(formatter, field, constraintValue));
+ 	}
+ 
+ 	private String buildMessage(MessageFormatter formatter, Field field, Void constraintValue) {
+ 		return formatter.format(constraintValue, field.getLabel());
+ 	}
+ 
+ 	public void render(Field field, Void constraintValue, MessageFormatter formatter, MarkupWriter writer,
+ 										 FormSupport formSupport) {
+ 		formSupport.addValidation(field, "foo", buildMessage(formatter, field, constraintValue), null);
+ 	}
+ }
+ }}}
+ === Create a resource file for validation messages ===
+ File ValidationMessages.properties
+ {{{
+ foo-not-allowed=Foo is not allowed
+ }}}
+ 
+ === Register both in your application ===
+ A Tapestry application is configured by a AppModule class (See the Tapestry Guide).
+ In the {{{AppModule}}} class add the following methods:
+ {{{
+   public static void contributeValidationMessagesSource(OrderedConfiguration<String> configuration) {
+     configuration.add("Default", "de/laliluna/example/components/ValidationMessages", "before:*");
+   }
+ 
+   public static void contributeFieldValidatorSource(MappedConfiguration<String, Validator> configuration) {
+     configuration.add("foo", new FooValidator());
+   }
+ }}}
+ That's it.
+ 
+ == Tapestry 4.0 ==
  
  this is a revised copy of a posing to the users mailing list by Scott F. Walter
  == 1. implementing a validator ==

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