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package org.macrocloud.kernel.toolkit.utils;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Queue;
import java.util.TimeZone;
import java.util.concurrent.ConcurrentLinkedQueue;


/**
 * 参考tomcat8中的并发DateFormat
 * 
 * {@link SimpleDateFormat}的线程安全包装器。
 * 不使用ThreadLocal，创建足够的SimpleDateFormat对象来满足并发性要求。
 * .
 *
 * @author macro
 */
public class ConcurrentDateFormat {
	
	/** The format. */
	private final String format;
	
	/** The locale. */
	private final Locale locale;
	
	/** The timezone. */
	private final TimeZone timezone;
	
	/** The queue. */
	private final Queue queue = new ConcurrentLinkedQueue<>();

	/**
	 * Instantiates a new concurrent date format.
	 *
	 * @param format the format
	 * @param locale the locale
	 * @param timezone the timezone
	 */
	private ConcurrentDateFormat(String format, Locale locale, TimeZone timezone) {
		this.format = format;
		this.locale = locale;
		this.timezone = timezone;
		SimpleDateFormat initial = createInstance();
		queue.add(initial);
	}

	/**
	 * Of.
	 *
	 * @param format the format
	 * @return the concurrent date format
	 */
	public static ConcurrentDateFormat of(String format) {
		return new ConcurrentDateFormat(format, Locale.getDefault(), TimeZone.getDefault());
	}

	/**
	 * Of.
	 *
	 * @param format the format
	 * @param timezone the timezone
	 * @return the concurrent date format
	 */
	public static ConcurrentDateFormat of(String format, TimeZone timezone) {
		return new ConcurrentDateFormat(format, Locale.getDefault(), timezone);
	}

	/**
	 * Of.
	 *
	 * @param format the format
	 * @param locale the locale
	 * @param timezone the timezone
	 * @return the concurrent date format
	 */
	public static ConcurrentDateFormat of(String format, Locale locale, TimeZone timezone) {
		return new ConcurrentDateFormat(format, locale, timezone);
	}

	/**
	 * Format.
	 *
	 * @param date the date
	 * @return the string
	 */
	public String format(Date date) {
		SimpleDateFormat sdf = queue.poll();
		if (sdf == null) {
			sdf = createInstance();
		}
		String result = sdf.format(date);
		queue.add(sdf);
		return result;
	}

	/**
	 * Parses the.
	 *
	 * @param source the source
	 * @return the date
	 * @throws ParseException the parse exception
	 */
	public Date parse(String source) throws ParseException {
		SimpleDateFormat sdf = queue.poll();
		if (sdf == null) {
			sdf = createInstance();
		}
		Date result = sdf.parse(source);
		queue.add(sdf);
		return result;
	}

	/**
	 * Creates the instance.
	 *
	 * @return the simple date format
	 */
	private SimpleDateFormat createInstance() {
		SimpleDateFormat sdf = new SimpleDateFormat(format, locale);
		sdf.setTimeZone(timezone);
		return sdf;
	}
}