前端采用vue，后端采用springboot+微服务+网关，进行对接时出现以下报错怎么解决Access to XMLHttpRequest at 'http://127.0.0.1:8090/user/admin/register' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

在Vue前端和Spring Boot后端中解决CORS问题，你可以尝试以下方法：

1. 后端配置CORS过滤器：在Spring Boot后端的网关服务中，添加一个CORS过滤器，处理跨域请求。你可以创建一个类实现`javax.servlet.Filter`接口，然后在`doFilter()`方法中设置响应头，包括`Access-Control-Allow-Origin`字段。示例代码如下：

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Component
public class CorsFilter implements Filter {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        HttpServletResponse httpResponse = (HttpServletResponse) response;

        httpResponse.setHeader("Access-Control-Allow-Origin", "*");
        httpResponse.setHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");
        httpResponse.setHeader("Access-Control-Max-Age", "3600");
        httpResponse.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization, X-Requested-With");

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

2. 配置Spring Security：如果你在后端使用了Spring Security来进行身份验证和授权，你可以在配置类中添加以下代码来解决CORS问题：

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.cors().and().csrf().disable();
    }

    @Bean
    public CorsConfigurationSource corsConfigurationSource() {
        CorsConfiguration configuration = new CorsConfiguration();
        configuration.setAllowedOrigins(Arrays.asList("*"));
        configuration.setAllowedMethods(Arrays.asList("GET", "POST", "PUT", "DELETE", "OPTIONS"));
        configuration.setAllowedHeaders(Arrays.asList("Content-Type", "Authorization", "X-Requested-With"));
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", configuration);
        return source;
    }
}

这样配置后，Spring Security将允许来自任何源的跨域请求。

3. 使用代理：在开发环境下，你可以在Vue的配置文件中设置代理，将前端请求转发到后端服务，从而避免浏览器的CORS限制。在`vue.config.js`文件中添加以下代码：

module.exports = {
  devServer: {
    proxy: {
      '/api': {
        target: 'http://127.0.0.1:8090', // 后端服务地址
        changeOrigin: true,
        pathRewrite: {
          '^/api': ''
        }
      }
    }
  }
}

然后，在前端代码中使用`/api`作为请求的基础路径，例如：`axios.post('/api/user/admin/register', data)`。

这些方法中的任何一种都可以帮助你解决CORS问题。你可以根据你的具体情况选择适合的方法。