SetCharacterEncodingFilter jsp字符过滤器

package com.demo.filter;
import javax.servlet.Filter;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import java.io.IOException;
public class SetCharacterEncodingFilter implements Filter {
  protected FilterConfig filterConfig;
  protected String encodingName;
  protected boolean enable;
  public SetCharacterEncodingFilter() {
    this.encodingName = "GBK";
    this.enable = false;
  }
  public void init(FilterConfig filterConfig) throws ServletException {
    this.filterConfig = filterConfig;
  }
  public void doFilter(ServletRequest request,
                       ServletResponse response,
                       FilterChain chain)
                    throws IOException, ServletException {
    request.setCharacterEncoding("GBK");
    response.setCharacterEncoding("GBK");
    chain.doFilter(request, response);
  }
  public void destroy() {
  }
}
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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.5" xsi:schemaLocation="http://java.sun.