1.導包

javax.servlet

2.編寫過濾器

package com.yl.filter;
​
import javax.servlet.*;
import java.io.IOException;
​
public class CharacterEncodingFilter implements Filter {
  //伺服器開啟的時候初始化
  public void init(FilterConfig filterConfig) throws ServletException {
    System.out.println("初始化");
   }
  
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
 
    request.setCharacterEncoding("utf-8");
    response.setCharacterEncoding("utf-8");
    response.setContentType("text/html;charset=UTF-8");
    System.out.println("CharacterEncodingFilter執行前");
    chain.doFilter(request,response);//讓請求繼續走，如果不寫，程式進行到這裡就會停止
    System.out.println("CharacterEncodingFilter執行後");
 
   }
​
  //伺服器關閉的時候銷燬
  public void destroy() {
    System.out.println("已銷燬");
   }
}
​

3.在web.xml中配置Filter過濾器