如何解决跨域问题，以及跨域预检未通过问题

has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: It does not have HTTP ok status.

最近在前后端联调时，当我通过axios在前端进行POST请求时，浏览器报如下错误：

has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: It does not have HTTP ok status.

乍一看是跨域问题，但其实并不是跨域问题。由于浏览器将CORS请求分为两类：简单请求（simple request）和非简单请求（not-simple-request）。非简单请求 会在正式通信之前，增加一次HTTP请求，称之为预检请求。浏览器会先发起OPTIONS方法到服务器，以获知服务器是否允许该实际请求。

这是在第一次预请求时候没有请求成功，预请求不成功。

先聊一下在SpringBoot项目中如何处理跨域问题：添加如下代码：

@Component
public class SimpleCORSFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE, HEAD,PUT");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "access-control-allow-origin, authority, content-type, version-info, X-Requested-With");
        chain.doFilter(req, res);
    }

    @Override
    public void init(FilterConfig filterConfig) {}

    @Override
    public void destroy() {}

}

其次如何解决has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: It does not have HTTP ok status.这个错误

@Component
public class SimpleCORSFilter implements Filter {

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE, HEAD,PUT");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "access-control-allow-origin, authority, content-type, version-info, X-Requested-With");
        HttpServletRequest request = (HttpServletRequest)req;
        if ("OPTIONS".equals(request.getMethod())) {
            response.setStatus(HttpServletResponse.SC_OK);
            return;
        }

        chain.doFilter(req, res);
    }

    @Override
    public void init(FilterConfig filterConfig) {}

    @Override
    public void destroy() {}

}