Spring的字符集过滤通过用于处理项目中的乱码问题，该过滤器位于org.springframework.web.filter包中，指向类CharacterEncodingFilter，CharacterEncodingFilter源代码如下：
/* * 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://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 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. * *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. *
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. *
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. *
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); }}
上述代码显示，在配置字符集过滤器时可设定两个参数的值，如下：
l encoding：字符集，即将过滤到的request的字符集设置为encoding指定的值，如UTF-8等，相当于：
request.setCharacterEncoding
l forceEncoding：字面意思是强制字符集，但你大可不必按字面意思理解，因为这个参数的值只不过是指定response的字符集是否也设置成encoding所指定的字符集，所以你可以选择设置为true或false，当值为true时，相当于
request.setCharacterEncoding(“”);response.setCharacterEncoding(“”);
当值为false时，相当于：
request.setCharacterEncoding(“”);
默认值为false。
示例：
characterEncodingFilter org.springframework.web.filter.CharacterEncodingFilter encoding UTF-8 forceEncoding true characterEncodingFilter /*
以上代码放置在web.xml中，相当于servlet中的：
request.setCharacterEncoding("UTF-8");response.setCharacterEncoding("UTF-8");