前端通过XHR请求后端服务时，出现了下图现象：
根据问题的描述可知，是遇到跨域问题了，为了支持跨域，需要在后端做一下处理，可以这样处理：
@Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; response.setHeader("Access-Control-Allow-Methods", "POST, GET, PATCH, DELETE, PUT, OPTIONS"); filterChain.doFilter(servletRequest, servletResponse); }
具体的添加过程，可以参考此链接
https://www.cnblogs.com/bien94/p/13188699.html
Method PUT is not allowed by Access-Control-Allow-Methods in preflight response