DateTimeFormatResolver.java

/*
 * Copyright 2013 Martin Kouba
 *
 * 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.trimou.engine.resolver.i18n;

import static org.trimou.engine.priority.Priorities.rightAfter;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Collections;
import java.util.Date;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.trimou.engine.config.ConfigurationKey;
import org.trimou.engine.config.SimpleConfigurationKey;
import org.trimou.engine.resolver.ArrayIndexResolver;
import org.trimou.engine.resolver.ResolutionContext;
import org.trimou.engine.resolver.TransformResolver;

/**
 * Basic date and time formatting resolver.
 *
 * Acceptable names:
 * <ul>
 * <li>format - format date and time with predefined MEDIUM pattern</li>
 * <li>formatShort - format date and time with predefined SHORT pattern</li>
 * <li>formatDate - format date with predefined MEDIUM pattern</li>
 * <li>formatCustom - format date and time with custom pattern</li>
 * </ul>
 *
 * @author Martin Kouba
 */
public class DateTimeFormatResolver extends TransformResolver {

    private static final Logger LOGGER = LoggerFactory
            .getLogger(DateTimeFormatResolver.class);

    public static final int DATE_TIME_FORMAT_RESOLVER_PRIORITY = rightAfter(ArrayIndexResolver.ARRAY_RESOLVER_PRIORITY);

    public static final ConfigurationKey CUSTOM_PATTERN_KEY = new SimpleConfigurationKey(
            DateTimeFormatResolver.class.getName() + ".customPattern",
            "M/d/yy h:mm a");

    static final String NAME_FORMAT = "format";

    static final String NAME_FORMAT_SHORT = "formatShort";

    static final String NAME_FORMAT_CUSTOM = "formatCustom";

    static final String NAME_FORMAT_DATE = "formatDate";

    private String customPattern;

    /**
     *
     */
    public DateTimeFormatResolver() {
        this(DATE_TIME_FORMAT_RESOLVER_PRIORITY);
    }

    /**
     *
     * @param priority
     */
    public DateTimeFormatResolver(int priority) {
        super(priority, NAME_FORMAT, NAME_FORMAT_CUSTOM, NAME_FORMAT_DATE,
                NAME_FORMAT_SHORT);
    }

    @Override
    public Object transform(Object contextObject, String name,
            ResolutionContext context) {

        Object formattableObject = getFormattableObject(contextObject);

        if (formattableObject == null) {
            return null;
        }

        if (NAME_FORMAT.equals(name)) {
            return format(DateFormat.MEDIUM, formattableObject);
        } else if (NAME_FORMAT_SHORT.equals(name)) {
            return format(DateFormat.SHORT, formattableObject);
        } else if (NAME_FORMAT_CUSTOM.equals(name)) {
            return formatCustom(formattableObject);
        }
        if (NAME_FORMAT_DATE.equals(name)) {
            return formatDate(DateFormat.MEDIUM, formattableObject);
        }
        return null;
    }

    @Override
    public void init() {
        super.init();
        customPattern = configuration
                .getStringPropertyValue(CUSTOM_PATTERN_KEY);
        LOGGER.info("Initialized [customPattern: {}]", customPattern);
    }

    @Override
    public Set<ConfigurationKey> getConfigurationKeys() {
        return Collections.singleton(CUSTOM_PATTERN_KEY);
    }

    private Object getFormattableObject(Object contextObject) {
        if (contextObject instanceof Date || contextObject instanceof Number) {
            return contextObject;
        } else if (contextObject instanceof Calendar) {
            return ((Calendar) contextObject).getTime();
        }
        return null;
    }

    private String format(int style, Object object) {
        return DateFormat.getDateTimeInstance(style, style, getCurrentLocale())
                .format(object);
    }

    private String formatDate(int style, Object object) {
        return DateFormat.getDateInstance(style, getCurrentLocale()).format(
                object);
    }

    private String formatCustom(Object object) {
        return new SimpleDateFormat(customPattern, getCurrentLocale())
                .format(object);
    }

}