JapaneseDateTag.java

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.BodyTagSupport;

import org.apache.commons.lang3.time.FastDateFormat;


public class JapaneseDateTag extends BodyTagSupport {
	private static final Locale JAPANESE_IMPERIAL = new Locale("ja", "JP", "JP");
	private static final long serialVersionUID = 1L;

	private String format;
	private boolean imperial = true;
	private String value;

	@Override
	public int doEndTag() throws JspException {
		try {
			pageContext.getOut().print(computeDisplay());
		} catch (IOException e) {
			throw new JspTagException(e);
		}
		return super.doEndTag();
	}

	public String getFormat() {
		return format;
	}

	public String getValue() {
		return value;
	}

	public boolean isImperial() {
		return imperial;
	}

	public void setFormat(String format) {
		this.format = format;
	}

	public void setImperial(boolean imperial) {
		this.imperial = imperial;
	}

	public void setValue(String value) {
		this.value = value;
	}

	protected Locale getLocale() {
		return imperial ? JAPANESE_IMPERIAL : Locale.JAPANESE;
	}

	protected String getOutputFormat() {
		return imperial ? "GGGGyyyy'年'MM'月'dd'日'" : "yyyy'年'MM'月'dd'日'";
	}

	private String computeDisplay() throws JspTagException {
		try {
			Date date = new SimpleDateFormat(format, Locale.US).parse(value);
			return FastDateFormat.getInstance(getOutputFormat(), getLocale()).format(date);
		} catch (ParseException pe) {
			throw new JspTagException(pe);
		}
	}
}