Spring boot rest service options 401 on oauth/token

You can add this CORS Filter to your project

    @Component
    @Order(Ordered.HIGHEST_PRECEDENCE)

    public class SimpleCORSFilter implements Filter {

    @Override
    public void init(FilterConfig fc) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp,
            FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) resp;
        HttpServletRequest request = (HttpServletRequest) req;
        response.setHeader("Access-Control-Allow-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, Content-Type, Authorization, credential, X-XSRF-TOKEN");

        if ("OPTIONS".equalsIgnoreCase(request.getMethod())) {
            response.setStatus(HttpServletResponse.SC_OK);
        } else {
            chain.doFilter(req, resp);
        }

    }

    @Override
    public void destroy() {
    }

 }

if you are using spring boot + Spring OAuth you must add

@Order(Ordered.HIGHEST_PRECEDENCE)

to your CORS filter

@Configuration
@Order(Ordered.HIGHEST_PRECEDENCE)
public class CORSFilter implements Filter {

    private FilterConfig config;

    public static final String CREDENTIALS_NAME = "Access-Control-Allow-Credentials";
    public static final String ORIGIN_NAME = "Access-Control-Allow-Origin";
    public static final String METHODS_NAME = "Access-Control-Allow-Methods";
    public static final String HEADERS_NAME = "Access-Control-Allow-Headers";
    public static final String MAX_AGE_NAME = "Access-Control-Max-Age";

    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp,
                         FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) resp;
        HttpServletRequest request = (HttpServletRequest) req;
        response.setHeader("Access-Control-Allow-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, Content-Type, Authorization, credential, X-XSRF-TOKEN");

        if ("OPTIONS".equalsIgnoreCase(request.getMethod())) {
            response.setStatus(HttpServletResponse.SC_OK);
        } else {
            chain.doFilter(req, resp);
        }

    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        config = filterConfig;
    }
}

Here is native Spring Framework solution:

@Bean
public CorsFilter corsFilter(CorsConfiguration config) {
    log.debug("Registering CORS filter");
    UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
    source.registerCorsConfiguration("/api/**", config);
    source.registerCorsConfiguration("/v2/api-docs", config);
    source.registerCorsConfiguration("/oauth/**", config);
    return new CorsFilter(source);
}