CharacterEncodingFilter主要用于处理请求中的乱码问题。
这个类的继承关系如下：
CharacterEncodingFilter的源码：
/*
* Copyright 2002-2015 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 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 (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.
*/
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);
}
}
这个类的功能在源码的注释中已经解释的非常清楚了，好好读一读！
通过源码我们可以看到在web.xml中配置CharacterEncodingFilter时可以配置两个参数：encoding和forceEncoding.
encoding表示使用的编码格式，一般肯定是使用UTF-8啦！
forceEncoding表示是否允许上面设置的encoding覆盖request和response中已经存在的编码方式。
使用方法：
<filter>
<filter-name>characterEncodingFilter</filter-name>
<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>
</filter-mapping>