Servlet 解决前端Axios跨域请求

1. 写一个过滤器就行

package com.qfedu.JDBC.Filter;

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

@WebFilter(filterName = "CORSFilter", urlPatterns = {
    
    "/*"})
//@Order(value = 1)
//@Configuration         这3个注解的作用 等同与web.xml 中配置的过滤映射 ，可以2选1
public class CorsFilter implements Filter {
    
    
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    
    
        System.out.println("初始化了");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)throws IOException, ServletException {
    
    
        System.out.println("Filter 过滤器 执行 了");
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, DELETE,PUT,GET,OPTIONS");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.addHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");

        filterChain.doFilter(request, response);

    }

    @Override
    public void destroy() {
    
    
        System.out.println("销毁了");
    }
}