一、创建过滤器类并实现Filter接口

import javax.servlet.Filter;

public class EncodingFilter implements Filter {

二、通过WebFilter注解配置过滤器拦截一切请求

@WebFilter({"/*"}) //过滤一切请求

三、在doFilter方法中统一设置编码方式并将请求放行

HttpServletRequest req = (HttpServletRequest) servletRequest;
HttpServletResponse resp = (HttpServletResponse) servletResponse;
//设置编码集，解决中文乱码问题
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
resp.setContentType("application/json;charset=utf8");

filterChain.doFilter(servletRequest, servletResponse); //请求放行

四、完整源代码

package filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter({"/*"}) //过滤一切请求
public class EncodingFilter implements Filter {

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进过滤器了");

        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;
        //设置编码集，解决中文乱码问题
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("application/json;charset=utf8");

        filterChain.doFilter(servletRequest, servletResponse); //请求放行
    }

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    public void destroy() {

    }
}