Vue는 어렵다…

1. post인데 url을 브라우저에 대고 바로 호출하면 당연히 get not supported 오류가 뜬다.

2. cors는 필터만 잘 써주면 된다.

   public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
      throws ServletException, IOException {
      HttpServletRequest request = (HttpServletRequest) servletRequest;
      ((HttpServletResponse) servletResponse).addHeader("Access-Control-Allow-Origin", "*");
      ((HttpServletResponse) servletResponse).addHeader("Access-Control-Allow-Methods","GET, OPTIONS, HEAD, PUT, POST");
      ((HttpServletResponse) servletResponse).addHeader("Access-Control-Allow-Headers","Origin, X-Requested-With, Content-Type, Accept");
      HttpServletResponse resp = (HttpServletResponse) servletResponse;
      if (request.getMethod().equals("OPTIONS")) {
          resp.setStatus(HttpServletResponse.SC_OK);
          return;
      }
      filterChain.doFilter(request, servletResponse);
   }