在主啟動類Application.java類裡面加入：

 private CorsConfiguration buildConfig() {
    CorsConfiguration corsConfiguration = new CorsConfiguration();
    corsConfiguration.addAllowedOrigin("*");
    corsConfiguration.addAllowedHeader("*");
    corsConfiguration.addAllowedMethod("*");
    return corsConfiguration;
  }

  /**
   * 跨域過濾器
   * @return
   */
  @Bean
  public CorsFilter corsFilter() {
    UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
    source.registerCorsConfiguration("/**", buildConfig()); // 4
    return new CorsFilter(source);
  }