setToken() {
    let token = localStorage.getItem('token') ? localStorage.getItem('token') : ''
    this.instance.defaults.headers.common['tokens'] = token
  }
// 使用axios添加requestHeaders參數(shù)。封裝到ajax請求中~

Access-Control-Allow-Headers: Content-Type, x-requested-with, X-Custom-Header, Authorization,token

@Override 
public void doFilter(ServletRequest req, ServletResponse resp,
        FilterChain chain) throws IOException, ServletException { 
    try { 
        HttpServletRequest hreq = (HttpServletRequest) req;  
        HttpServletResponse hresp = (HttpServletResponse) resp;
 
        //跨域
        hresp.setHeader("Access-Control-Allow-Origin", "*"); 
 
        //跨域 Header 
        hresp.setHeader("Access-Control-Allow-Methods", "*"); 
        hresp.setHeader("Access-Control-Allow-Headers", "Content-Type,TOKENS");　　// 在這里配置你要定義的參數(shù)         
 
        // 瀏覽器是會先發(fā)一次options請求，如果請求通過，則繼續(xù)發(fā)送正式的post請求 
        // 配置options的請求返回
 
        if (hreq.getMethod().equals("OPTIONS")) { 
            hresp.setStatus(HttpStatus.SC_OK); 
            // hresp.setContentLength(0); 
            hresp.getWriter().write("OPTIONS returns OK"); 
            return; 
        }
 
        // Filter 只是鏈?zhǔn)教幚?，請求依然轉(zhuǎn)發(fā)到目的地址。
 
        chain.doFilter(req, resp); 
    } catch (Exception e) { 
        e.printStackTrace(); 
    } 
}

hresp.setHeader("Access-Control-Allow-Headers", "Content-Type,TOKENS");

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        chain.doFilter(new CustomeizedRequest((HttpServletRequest) request), response);
    } 
    private class CustomeizedRequest extends HttpServletRequestWrapper { 
        public CustomeizedRequest(HttpServletRequest request) {
            super(request);
        }
 
        @Override
        public Enumeration<String> getHeaders(String name) {
            if (null != name && name.equals("Content-Type")) {
                return new Enumeration<String>() {
                    private boolean hasGetted = false; 
                    @Override
                    public String nextElement() {
                        if (hasGetted) {
                            throw new NoSuchElementException();
                        } else {
                            hasGetted = true;
                            return "application/json;charset=utf-8";
                        }
                    } 
                    @Override
                    public boolean hasMoreElements() {
                        return !hasGetted;
                    }
                };
            }
            return super.getHeaders(name);
        }
    }