setcharacterencodingfilter.java~2~

一个oracle和JSP做的论坛

/*
 * 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 hcit.common;

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;

// import javax.servlet.UnavailableException;

/**
 * <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: 2007/12/10 07:00:37 $
 */

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);

        }

}