zkoss/zk

/* TimeZones.java

{{IS_NOTE
    Purpose:
        
    Description:
        
    History:
        Mon Jun 12 12:17:03     2006, Created by tomyeh
}}IS_NOTE

Copyright (C) 2006 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
}}IS_RIGHT
*/
package org.zkoss.util;

import java.util.TimeZone;

/**
 * Utilities to access time-zone.
 *
 * @author tomyeh
 */
public class TimeZones {
    private static final
        InheritableThreadLocal<TimeZone> _thdTZone = new InheritableThreadLocal<TimeZone>();
    /** Returns the current time zone; never null.
     * This is the time zone that every other objects shall use,
     * unless they have special consideration.
     *
     * <p>Default: If {@link #setThreadLocal} was called with non-null,
     * the value is returned. Otherwise, TimeZone.getDefault() is returned,
     */
    public static final TimeZone getCurrent() {
        final TimeZone l = _thdTZone.get();
        return l != null ? l: TimeZone.getDefault();
    }
    /**
     * Sets the time-zone for the current thread only.
     *
     * <p>Each thread could have an independent time zone, called
     * the thread time zone.
     *
     * <p>When Invoking this method under a thread that serves requests,
     * remember to clean up the setting upon completing each request.
     *
     * <pre><code>TimeZone old = TimeZones.setThreadLocal(newValue);
     *try { 
     *  ...
     *} finally {
     *  TimeZones.setThreadLocal(old);
     *}</code></pre>
     *
     * @param timezone the thread time zone; null to denote no thread time zone
     * (and the system's timezone will be used instead)
     * @return the previous thread time zone, or null if no previous time zone
     */
    public static final TimeZone setThreadLocal(TimeZone timezone) {
        final TimeZone old = _thdTZone.get();
        _thdTZone.set(timezone);
        return old;
    }
    /**
     * Returns the time zone defined by {@link #setThreadLocal}.
     *
     * @since 3.0.0
     * @see #getCurrent
     */
    public static final TimeZone getThreadLocal() {
        return _thdTZone.get();
    }

    /** Returns the time by specifying the offset in minutes.
     *
     * <p>For example, the following are equivalent.
     *<pre><code>
     *TimeZone.getTimeZone("GMT+8");
     *TimeZones.getTimeZone(480);
     *</code></pre>
     *
     * @param ofsmins the offset in minutes.
     */
    public static final TimeZone getTimeZone(int ofsmins) {
        final StringBuffer sb = new StringBuffer(8).append("GMT");
        if (ofsmins >= 0) {
            sb.append('+');
        } else {
            sb.append('-');
            ofsmins = -ofsmins;
        }
        final int hr = ofsmins / 60, min = ofsmins % 60;
        if (min == 0) {
            sb.append(hr);
        } else {
            if (hr < 10) sb.append('0');
            sb.append(hr).append(':');
            if (min < 10) sb.append('0');
            sb.append(min);
        }
        return TimeZone.getTimeZone(sb.toString());
    }
}