java字符编码过滤器

统一项目的编码,字符过滤器:

SetCharacterEncodingFilter.java

/*
 * Copyright 2004 The Apache Software Foundation
 *
 * 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 com.easyweb.web.character;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * <p>
 * Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding. Configuration of this filter is based on the
 * following initialization parameters:
 * </p>
 * <ul>
 * <li><strong>encoding</strong> - The character encoding to be configured for
 * this request, either conditionally or unconditionally based on the
 * <code>ignore</code> initialization parameter. This parameter is required,
 * so there is no default.</li>
 * <li><strong>ignore</strong> - If set to "true", any character encoding
 * specified by the client is ignored, and the value returned by the
 * <code>selectEncoding()</code> method is set. If set to "false,
 * <code>selectEncoding()</code> is called <strong>only</strong> if the
 * client has not already specified an encoding. By default, this parameter is
 * set to "true".</li>
 * </ul>
 *
 * <p>
 * Although this filter can be used unchanged, it is also easy to subclass it
 * and make the <code>selectEncoding()</code> method more intelligent about
 * what encoding to choose, based on characteristics of the incoming request
 * (such as the values of the <code>Accept-Language</code> and
 * <code>User-Agent</code> headers, or a value stashed in the current user's
 * session.
 * </p>
 *
 * @author Craig McClanahan
 * @version $Revision: 1.1 $ $Date: 2010/10/13 05:38:55 $
 */

public class SetCharacterEncodingFilter implements Filter {

 // ----------------------------------------------------- Instance Variables

 /**
  * The default character encoding to set for requests that pass through this
  * filter.
  */
 protected String encoding = null;

 /**
  * The filter configuration object we are associated with. If this value is
  * null, this filter instance is not currently configured.
  */
 protected FilterConfig filterConfig = null;

 /**
  * Should a character encoding specified by the client be ignored?
  */
 protected boolean ignore = true;

 // --------------------------------------------------------- Public Methods

 /**
  * Take this filter out of service.
  */
 public void destroy() {

  this.encoding = null;
  this.filterConfig = null;

 }

 /**
  * Select and set (if specified) the character encoding to be used to
  * interpret request parameters for this request.
  *
  * @param request
  *            The servlet request we are processing
  * @param result
  *            The servlet response we are creating
  * @param chain
  *            The filter chain we are processing
  *
  * @exception IOException
  *                if an input/output error occurs
  * @exception ServletException
  *                if a servlet error occurs
  */
 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {

  // Conditionally select and set the character encoding to be used
  if (ignore || (request.getCharacterEncoding() == null)) {
   String encoding = selectEncoding(request);
   if (encoding != null)
    request.setCharacterEncoding(encoding);
  }

  // Pass control on to the next filter
  chain.doFilter(request, response);

 }

 /**
  * Place this filter into service.
  *
  * @param filterConfig
  *            The filter configuration object
  */
 public void init(FilterConfig filterConfig) throws ServletException {

  this.filterConfig = filterConfig;
  this.encoding = filterConfig.getInitParameter("encoding");
  String value = filterConfig.getInitParameter("ignore");
  if (value == null)
   this.ignore = true;
  else if (value.equalsIgnoreCase("true"))
   this.ignore = true;
  else if (value.equalsIgnoreCase("yes"))
   this.ignore = true;
  else
   this.ignore = false;

 }

 // ------------------------------------------------------ Protected Methods

 /**
  * Select an appropriate character encoding to be used, based on the
  * characteristics of the current request and/or filter initialization
  * parameters. If no character encoding should be set, return
  * <code>null</code>.
  * <p>
  * The default implementation unconditionally returns the value configured
  * by the <strong>encoding</strong> initialization parameter for this
  * filter.
  *
  * @param request
  *            The servlet request we are processing
  */
 protected String selectEncoding(ServletRequest request) {

  return (this.encoding);
 }
}