JavaWeb——字符编码过滤器

编写一个EncodingFilter

1.读取web.xml文件中配置的当前WEB应用的初始化参数encoding

2.指定请求的字符编码为1读取到的编码

3.调用chain.doFilter()方法"放行"请求

   web.xml

    <context-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </context-param>

  <filter>
        <filter-name>EncodingFilter</filter-name>
        <filter-class>com.demo.filter.EncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>EncodingFilter</filter-name>
        <url-pattern>/filter/b.jsp</url-pattern>
    </filter-mapping>

　　

EncodingFilter

package com.demo.filter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class EncodingFilter extends HttpFilter {

    private String encoding;
    @Override
    protected void init() {
        encoding = getFilterConfig().getServletContext().getInitParameter("encoding");
        System.out.println(encoding);
    }

    @Override
    public void doFilter(HttpServletResponse response, HttpServletRequest request, FilterChain filterChain) throws IOException, ServletException {
        request.setCharacterEncoding(encoding);
        filterChain.doFilter(request,response);
    }
}