Filter

添加过滤器
在controler 创一个java文件和servlet是并列的只不过它是@WebFilter 实现Filter接口分清楚就好直接复制就能用
package com.etoak.student.controller;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebFilter("/*")
public class CrossFilter implements Filter{
    
    

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    
    

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    
    
        System.out.println("Filter过滤！！");
        HttpServletResponse httpResponse = (HttpServletResponse) response;

        // 允许所有的请求域名访问我们的跨域资源，可以固定单个或者多个内容
        httpResponse.setHeader("Access-Control-Allow-Origin", "*");//
        // httpResponse.setHeader("Access-Control-Allow-Origin", "http://localhost:9090");// 允许所有的请求域名访问我们的跨域资源，可以固定单个或者多个内容
        httpResponse.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE,PUT");// 允许何种请求方法访问该跨域资源服务器
        httpResponse.setHeader("Access-Control-Max-Age", "3600");// 预检请求的有效期，单位为秒。有效期内，不会重复发送预检请求
        httpResponse.addHeader("Access-Control-Allow-Headers",
                "Accept,Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With");// 允许所有的请求header访问，可以自定义设置任意请求头信息 后期加上 authorization
        httpResponse.setHeader("Access-Control-Allow-Credentials", "true");// 是否允许用户发送、处理cookie
        //如果额外设置自己的头需要在这定义
        httpResponse.setHeader("Access-Control-Expose-Headers", "Access-Token");
        chain.doFilter(request, httpResponse);
    }

    @Override
    public void destroy() {
    
    

    }
}
servlet解决跨域问题,后端如何跨域?

Filter

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