JsfLabelMessageInterpolator.java

/*
 * Copyright 2017 OmniFaces
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */
package org.omnifaces.validator;

import static javax.validation.Validation.byDefaultProvider;
import static org.omnifaces.util.Components.getCurrentComponent;
import static org.omnifaces.util.Components.getLabel;
import static org.omnifaces.util.Faces.getLocale;
import static org.omnifaces.util.Faces.hasContext;

import java.util.Locale;

import javax.validation.MessageInterpolator;


/**
 * <p>
 * Unlike native JSF validation error messages, in a bean validation message by default the label of the component where
 * a validation constraint violation originated from can not be displayed in the middle of a message. Using the
 * <code>javax.faces.validator.BeanValidator.MESSAGE</code> bundle key such label can be put in front or behind the
 * message, but that's it. With this {@link JsfLabelMessageInterpolator} a label can appear in the middle of a message,
 * by using the special placeholder <code>{jsf.label}</code> in bean validation messages.
 * <p>
 * Note that Bean Validation is not only called from within JSF, and as such JSF might not be available. If JSF
 * is not available occurrences of <code>{jsf.label}</code> will be replaced by an empty string. The user should take
 * care that messages are compatible with both situations if needed.
 * <p>
 * This message interpolator is <strong>not</strong> needed for putting a component label before or after a bean
 * validation message. That functionality is already provided by JSF itself via the
 * <code>javax.faces.validator.BeanValidator.MESSAGE</code> key in any resource bundle known to JSF.
 *
 * <h3>Installation</h3>
 * <p>
 * Create a <code>/META-INF/validation.xml</code> file in WAR with the following contents:
 *
 * <pre>
 * <?xml version="1.0" encoding="UTF-8"?>
 * <validation-config
 *     xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
 *     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 *     xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration validation-configuration-1.0.xsd"
 * >
 *     <message-interpolator>org.omnifaces.validator.JsfLabelMessageInterpolator</message-interpolator>
 * </validation-config>
 * </pre>
 *
 * <h3>Usage</h3>
 * <p>As an example, the customization of <code>@Size</code> in <code>ValidationMessages.properties</code>:
 * <pre>
 * javax.validation.constraints.Size.message = The size of {jsf.label} must be between {min} and {max} characters
 * </pre>
 *
 * @author Arjan Tijms
 * @since 1.5
 */
public class JsfLabelMessageInterpolator implements MessageInterpolator {

	private final MessageInterpolator wrapped;

	public JsfLabelMessageInterpolator() {
		wrapped = byDefaultProvider().configure().getDefaultMessageInterpolator();
	}

	@Override
	public String interpolate(String messageTemplate, Context context) {
		return interpolate(messageTemplate, context, hasContext() ? getLocale() : Locale.getDefault());
	}

	@Override
	public String interpolate(String messageTemplate, Context context, Locale locale) {
		String message = wrapped.interpolate(messageTemplate, context, locale);

		if (message.contains("{jsf.label}")) {

			String label = "";
			if (hasContext()) {
				label = getLabel(getCurrentComponent());
			}

			message = message.replace("{jsf.label}", label);
		}

		return message;
	}

}