charsets.java

非常接近C/S操作方式的Java Ajax框架－ZK 用ZK框架使你的B/S应用程序更漂亮更易操作。 官网：www.zkoss.org

/* Charsets.java

{{IS_NOTE
	Purpose:
		
	Description:
		
	History:
		Wed Jan  5 13:55:30     2005, Created by tomyeh
}}IS_NOTE

Copyright (C) 2004 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
	This program is distributed under GPL Version 2.0 in the hope that
	it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.web.servlet;

import java.util.Locale;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.zkoss.lang.Objects;
import org.zkoss.lang.SystemException;
import org.zkoss.util.Locales;
import org.zkoss.util.logging.Log;

import org.zkoss.web.Attributes;

/**
 * Utilities to handle characters
 *
 * @author tomyeh
 */
public class Charsets {
	private static final Log log = Log.lookup(Charsets.class);
	private static final String ATTR_SETUP = "org.zkoss.web.charset.setup";

	/** Whether the container is servlet 2.3 or earlier. */
	private static boolean _svl23;
	private static final String _uriCharset;
	static {
		String cs = System.getProperty("org.zkoss.web.uri.charset", null);
		if (cs == null || cs.length() == 0)
			cs = "UTF-8"; //Default: UTF-8
		_uriCharset = cs;
	}

	/** Returns the charset used to encode URI and query string.
	 */
	public static final String getURICharset() {
		return _uriCharset;
	}

	/** Sets up the charset for the request and response based on
	 * {@link #getPreferredLocale}. After setting up, you shall invoke
	 * {@link #cleanup} before exiting.
	 *
	 * <pre><code> final Object old = setup(request, response);
	 * try {
	 *	  ....
	 * } finally {
	 *    cleanup(old);
	 * }
	 *
	 * <p>It is OK to call this method multiple time, since it is smart
	 * enough to ignore redudant calls.
	 *
	 * <p>{@link CharsetFilter} actually use this method to setup
	 * the proper charset and locale. By mapping {@link CharsetFilter} to
	 * all servlets, the encoding charset could be prepared correctly.
	 * However, if you are writing libraries to be as independent of
	 * web.xml as possible, you might choose to invoke this method directly.
	 *
	 * @param charset the response's charset. If null or empty,
	 * response.setCharacterEncoding won't be called, i.e., the container's
	 * default is used.
	 * @return an object that must be passed to {@link #cleanup}
	 */
	public static final
	Object setup(ServletRequest request, ServletResponse response, String charset) {
		if (hasSetup(request)) //processed before?
			return Objects.UNKNOWN;

		final Locale locale = getPreferredLocale(request);
		response.setLocale(locale);
		if (!_svl23 && charset != null && charset.length() > 0) {
			try {
				response.setCharacterEncoding(charset);
				//if null, the mapping defined in web.xml is used
			} catch (AbstractMethodError ex) {
				_svl23 = true;
			} catch (NoSuchMethodError ex) {
				_svl23 = true;
			} catch (Throwable ex) {
				final String v = response.getCharacterEncoding();
				if (!Objects.equals(v, charset))
					log.warning("Unable to set response's charset: "+charset+" (current="+v+')', ex);
			}
		}

		if (request.getCharacterEncoding() == null) {
			charset = response.getCharacterEncoding();
			try {
				request.setCharacterEncoding(charset);
			} catch (Throwable ex) {
				final String v = request.getCharacterEncoding();
				if (!Objects.equals(v, charset))
					log.warning("Unable to set request's charset: "+charset+" (current="+v+')', ex);
			}
		}

		markSetup(request, true);
		return Locales.setThreadLocal(locale);
	}
	/** Cleans up what has been set in {@link #setup}.
	 * Some invocation are not undo-able, so this method only does the basic
	 * cleanups.
	 *
	 * @param old the value must be the one returned by the last call to
	 * {@link #setup}.
	 */
	public static final void cleanup(ServletRequest request, Object old) {
		if (old != Objects.UNKNOWN) {
			Locales.setThreadLocal((Locale)old);
			markSetup(request, false);
		}
	}
	/** Returns whether the specified request has been set up, i.e.,
	 * {@link #setup} is called
	 *
	 * <p>It is rarely needed to call this method, because it is called
	 * automatically by {@link #setup}.
	 */
	public static final boolean hasSetup(ServletRequest request) {
		return request.getAttribute(ATTR_SETUP) != null; //processed before?
	}
	/** Marks the specified request whether it has been set up, i.e.,
	 * {@link #setup} is called.
	 *
	 * <p>It is rarely needed to call this method, because it is called
	 * automatically by {@link #setup}.
	 */
	public static final void markSetup(ServletRequest request, boolean setup) {
		if (setup) request.setAttribute(ATTR_SETUP, Boolean.TRUE);
		else request.removeAttribute(ATTR_SETUP);
	}

	/** Returns the preferred locale of the specified request.
	 * You rarely need to invoke this method directly, because it is done
	 * automatically by {@link #setup}.
	 *
	 * <ol>
	 * <li>It checks whether any attribute stored in HttpSession called
	 * {@link Attributes#PREFERRED_LOCALE}. If so, return it.</li>
	 * <li>Otherwise, use ServletRequest.getLocale().</li>
	 * </ol>
	 */
	public static final Locale getPreferredLocale(ServletRequest request) {
		if (request instanceof HttpServletRequest) {
			final HttpSession sess =
				((HttpServletRequest)request).getSession(false);
			if (sess != null) {
				final Locale l =
					(Locale)sess.getAttribute(Attributes.PREFERRED_LOCALE);
				if (l != null)
					return l;
			}
		}

		final Locale l = request.getLocale();
		return l != null ? l: Locale.getDefault();
	}
	/** Sets the preferred locale for the current session of the specified
	 * request.
	 * @param locale the preferred Locale. If null, it means no preferred
	 * locale (and then {@link #getPreferredLocale} use request.getLocale
	 * instead).
	 */
	public static final
	void setPreferredLocale(ServletRequest request, Locale locale) {
		if (request instanceof HttpServletRequest) {
			final HttpSession sess =
				((HttpServletRequest)request).getSession(); //auto-create
			if (locale != null)
				sess.setAttribute(Attributes.PREFERRED_LOCALE, locale);
			else
				sess.removeAttribute(Attributes.PREFERRED_LOCALE);
		}
	}
}