Java CharacterEncodingFilter过滤器的理解和配置案例详解

< filter >

         < filter-name >characterEncodingFilter</ filter-name >

         <!--配置转码，将编码都转为UTF-8-->

         < filter-class >org.springframework.web.filter.CharacterEncodingFilter</ filter-class >

         < init-param >

             < param-name >encoding</ param-name >

             < param-value >UTF-8</ param-value >

         </ init-param >

         < init-param >

             < param-name >forceEncoding</ param-name >

             < param-value >true</ param-value >

         </ init-param >

     </ filter >

     < filter-mapping >

         < filter-name >characterEncodingFilter</ filter-name >

         < url-pattern >/*</ url-pattern > <!-- 拦截路径-->

     </ filter-mapping >

/*

  * Copyright 2002-2007 the original author or authors.

  *

  * 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://HdhCmsTestapache.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 org.springframework.web.filter;

import java.io.IOException;

import javax.servlet.FilterChain;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

  * Servlet 2.3/2.4 Filter that allows one to specify a character encoding for

  * requests. This is useful because current browsers typically do not set a

  * character encoding even if specified in the HTML page or form.

  *

  * <p>This filter can either apply its encoding if the request does not

  * already specify an encoding, or enforce this filter's encoding in any case

  * ("forceEncoding"="true"). In the latter case, the encoding will also be

  * applied as default response encoding on Servlet 2.4+ containers (although

  * this will usually be overridden by a full content type set in the view).

  *

  * @author Juergen Hoeller

  * @since 15.03.2004

  * @see #setEncoding

  * @see #setForceEncoding

  * @see javax.servlet.http.HttpServletRequest#setCharacterEncoding

  * @see javax.servlet.http.HttpServletResponse#setCharacterEncoding

  */

public class CharacterEncodingFilter extends OncePerRequestFilter {

     private String encoding;

     private boolean forceEncoding = false;

     /**

      * Set the encoding to use for requests. This encoding will be passed into a

      * {@link javax.servlet.http.HttpServletRequest#setCharacterEncoding} call.

      * <p>Whether this encoding will override existing request encodings

      * (and whether it will be applied as default response encoding as well)

      * depends on the {@link #setForceEncoding "forceEncoding"} flag.

      */

     public void setEncoding(String encoding) {

         this.encoding = encoding;

     }

     /**

      * Set whether the configured {@link #setEncoding encoding} of this filter

      * is supposed to override existing request and response encodings.

      * <p>Default is "false", i.e. do not modify the encoding if

      * {@link javax.servlet.http.HttpServletRequest#getCharacterEncoding()}

      * returns a non-null value. Switch this to "true" to enforce the specified

      * encoding in any case, applying it as default response encoding as well.

      * <p>Note that the response encoding will only be set on Servlet 2.4+

      * containers, since Servlet 2.3 did not provide a facility for setting

      * a default response encoding.

      */

     public void setForceEncoding( boolean forceEncoding) {

         this .forceEncoding = forceEncoding;

     }

     @Override

     protected void doFilterInternal(

             HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)

             throws ServletException, IOException {

         if ( this .encoding != null && ( this .forceEncoding || request.getCharacterEncoding() == null )) {

             request.setCharacterEncoding( this .encoding);

             if ( this .forceEncoding) {

                 response.setCharacterEncoding( this .encoding);

             }

         }

         filterChain.doFilter(request, response);

     }

}

request.setCharacterEncoding( "" )

request.setCharacterEncoding( "" ); 

response.setCharacterEncoding( "" );

request.setCharacterEncoding( "" );