PreferenceWriter.java

/**
 * Copyright 2005-2014 Restlet
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet.engine.header;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import org.restlet.data.Parameter;
import org.restlet.data.Preference;

/**
 * Preference header writer.
 * 
 * @author Jerome Louvel
 */
public class PreferenceWriter extends HeaderWriter<Preference<?>> {
    /**
     * Indicates if the quality value is valid.
     * 
     * @param quality
     *            The quality value.
     * @return True if the quality value is valid.
     */
    public static boolean isValidQuality(float quality) {
        return (quality >= 0F) && (quality <= 1F);
    }

    /**
     * Writes a list of preferences with a comma separator.
     * 
     * @param prefs
     *            The list of preferences.
     * @return The formatted list of preferences.
     * @throws IOException
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static String write(List prefs) {
        return new PreferenceWriter().append(prefs).toString();
    }

    @Override
    public PreferenceWriter append(Preference<?> pref) {
        append(pref.getMetadata().getName());

        if (pref.getQuality() < 1F) {
            append(";q=");
            appendQuality(pref.getQuality());
        }

        if (pref.getParameters() != null) {
            Parameter param;

            for (Iterator<Parameter> iter = pref.getParameters().iterator(); iter
                    .hasNext();) {
                param = iter.next();

                if (param.getName() != null) {
                    append(';').append(param.getName());

                    if ((param.getValue() != null)
                            && (param.getValue().length() > 0)) {
                        append('=').append(param.getValue());
                    }
                }
            }
        }

        return this;
    }

    /**
     * Formats a quality value.<br>
     * If the quality is invalid, an IllegalArgumentException is thrown.
     * 
     * @param quality
     *            The quality value as a float.
     * @return This writer.
     */
    public PreferenceWriter appendQuality(float quality) {
        if (!isValidQuality(quality)) {
            throw new IllegalArgumentException(
                    "Invalid quality value detected. Value must be between 0 and 1.");
        }

        // [ifndef gwt]
        java.text.NumberFormat formatter = java.text.NumberFormat
                .getNumberInstance(java.util.Locale.US);
        formatter.setMaximumFractionDigits(2);
        append(formatter.format(quality));
        // [enddef]

        return this;
    }

}