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>
 
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;
 

public class CharacterEncodingFilter extends OncePerRequestFilter {
 
	private String encoding;
 
	private boolean forceEncoding = false;
 
 
	
	public void setEncoding(String encoding) {
		this.encoding = 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("");