解决No 'Access-Control-Allow-Origin' header is present on the requested resource.跨域问题（后台(java)解决方法）

附：前端常见跨域解决方案（全）

跨域错误

解决方法

在后台写一个过滤器来改写请求头

附上一个前端不知所以然的后台java代码：

 public class CorsFilter implements Filter {
     @Override
     public void init(FilterConfig filterConfig) throws ServletException {

     }

     @Override
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
         HttpServletResponse response = (HttpServletResponse) servletResponse;
         HttpServletRequest request = (HttpServletRequest)servletRequest;

         String origin = request.getHeader("Origin");
         response.setHeader("Access-Control-Allow-Origin", origin);
         response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
         response.setHeader("Access-Control-Max-Age", "3600");
         // response.setHeader("Access-Control-Allow-Headers", "x-requested-with,Authorization");
         response.setHeader("Access-Control-Allow-Headers", "Content-Type,Access-Token"); // 解决vue-axios请求报错问题
         response.setHeader("Access-Control-Allow-Credentials", "true");
         String method = request.getMethod();
         if(method.equalsIgnoreCase("OPTIONS")){
             servletResponse.getOutputStream().write("Success".getBytes("utf-8"));
         }else{
             filterChain.doFilter(servletRequest, servletResponse);
         }
     }

     @Override
     public void destroy() {

     }
 }