NOTE: This is outdated information that applies only to Tapestry 4. For current information see http://tapestry.apache.org/input-validation.html.

Creating a Translator is very similar to CreatingCustomValidators.

1. Extend Abstract Translator

The important part is to implement the formatObject and parseText methods to convert between your object and string.

In my example I have a boolean object that is the gender of someone represented by the 1 character strings M and F, defaulting to M when undefined. 

package uk.org.chandlerfamily.tapestry.translators;

import java.util.Locale;

import org.apache.tapestry.form.IFormComponent;
import org.apache.tapestry.form.ValidationMessages;
import org.apache.tapestry.form.translator.AbstractTranslator;
import org.apache.tapestry.valid.ValidatorException;

public class Gender extends AbstractTranslator
{
	
	private String _parameter;
	
	public Gender()
	{
		super();
	}

	public Gender(String initializer)
	{
		super(initializer);
	}

	public void setParameter(String parameter)
	{
		this._parameter = parameter;
	}
	
	public String getParameter()
	{
		return _parameter;
	}

	public String formatObject(IFormComponent arg0, Locale arg1, Object arg2)
	{
		if (arg2 == null)
			return "M";

		return (Boolean) arg2 ? "M" : "F";
	}

	public Object parseText(IFormComponent field, ValidationMessages messages,
			String text) throws ValidatorException
	{

		String [] args = new String[1];
		args[0] = text;

		if (!text.equalsIgnoreCase("M") && !text.equalsIgnoreCase("F"))
		{
			throw new ValidatorException(messages.formatValidationMessage(getMessage(), "invalid-format", args));	
		}

		return text.equalsIgnoreCase("M");
	}
}

Note: I haven't managed to figure out how to create new message keys. The invalid-format message key is a standard tapestry one.

2. Configure the translator in hivemodule.xml

Use the contribution element, with a bean element inside. You can put more than one bean element inside if you have multiple translators

<contribution configuration-id="tapestry.form.translator.Translators">
	<bean name="gender" class="uk.org.chandlerfamily.tapestry.translators.Gender" />
</contribution>

3. Use in your templates

use the translator:beanName to access the translator - with the value parameter being the translated object type.

			<td><span jwcid="@FieldLabel"
				field="component:gender" >Gender:</span></td>
			<td><input  jwcid="gender@TextField" 
				value="ognl:gender" 
				size="1"
				translator="translator:gender"
				displayName="Gender" /></td>

and in your class - see how I have used a real method in an abstract class to create a default value of true for this parameter (not sure if this is the correct way to do it)

public abstract class Create extends BasePage  {
	
	private boolean _gender = true;  //gives a default value
	
	public boolean getGender() {
		return _gender;
	}
	
	public void setGender(boolean gender) {
		this._gender = gender;
	}
...

4. Configurable Translators

The translator factory relies on Hivemind's BeanFactory which enables passing a single String to a bean constructor. Implement a constructor which takes a single String as a parameter, and use the syntax 

<binding name="translator" value="translator:gender,parameter"/>

This didn't work for me: I instead used the setter/getter ("setParameter()"/"getParameter()") in the translator class and the syntax 

<binding name="translator" value="translator:gender,parameter=value"/>
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