解决：The 'Access-Control-Allow-Origin' header contains multiple values'x

跨域问题报错：

Access to XMLHttpRequest at 'http://xx.xx.xx.xx/getUser' from origin 
'http://ergouzi.fun' has been blocked by CORS policy: 
The 'Access-Control-Allow-Origin' header contains multiple values 
'http://ergouzi.fun, *, http://ergouzi.fun', but only one is allowed.

1. 为了解决跨域问题，我在服务端代码中加了个过滤器：

package gentle.filter;

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

/**
 * 解决跨域设置
 * （可把此设置放在 nginx 中，但只能设置一处）
 *
 * @author silence
 * @date 2018/12/11 15:19
 */

@WebFilter(filterName = "requestFilter", urlPatterns = {"/*"})
public class RequestFilter implements Filter {

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

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpServletRequest request = (HttpServletRequest) servletRequest;

        // 此处 setHeader、addHeader 方法都可用。但 addHeader时写多个会报错：“...,but only one is allowed”
        // response.setHeader("Access-Control-Allow-Origin", "*");
        response.addHeader("Access-Control-Allow-Origin", request.getHeader("origin"));
        // 解决预请求（发送2次请求），此问题也可在 nginx 中作相似设置解决。
        response.setHeader("Access-Control-Allow-Headers", "x-requested-with,Cache-Control,Pragma,Content-Type,Token, Content-Type");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        String method = request.getMethod();
        if (method.equalsIgnoreCase("OPTIONS")) {
            servletResponse.getOutputStream().write("Success".getBytes("utf-8"));
        } else {
            filterChain.doFilter(servletRequest, servletResponse);
        }
    }

    @Override
    public void destroy() {

    }

}

2. 同时在 nginx 中也作了相关配置：

add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, PUT, DELETE';
add_header 'Access-Control-Allow-Headers' 'Content-Type';
...

3. 运行报错如题。

4. 解决：此错表示设置重复，只允许设置一种，去除多余设置，保留一种即可。选择第1点中方法，或者第2点中方法都可以。

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跨域相关知识点解说： https://blog.csdn.net/jiangyu1013/article/details/84315748

PS 跨域问题解决也见文章：解决跨域问题：No 'Access-Control-Allow-Origin' header is present on the requested resource.