过滤器

 

1.导包

javax.servlet

2.编写过滤器

package com.yl.filter;
​
import javax.servlet.*;
import java.io.IOException;
​
public class CharacterEncodingFilter implements Filter {
    //服务器开启的时候初始化
    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执行前");
        chain.doFilter(request,response);//让请求继续走，如果不写，程序进行到这里就会停止
        System.out.println("CharacterEncodingFilter执行后");
    }
​
    //服务器关闭的时候销毁
    public void destroy() {
        System.out.println("已销毁");
    }
}
​

3.在web.xml中配置Filter过滤器

<filter>
    <filter-name>encoding</filter-name>
    <filter-class>com.yl.filter.CharacterEncodingFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>