前后端分离的项目，使用Ajax请求可能出现跨域的问题。

 

Access to XMLHttpRequest at 'http://xxx:8089/hzes/en/spectaculars/getAllEnergyDayConsume?stationId=8605320001' from origin 'http://127.0.0.1:8081' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

跨域的时候所创建的session是不会被浏览器保存下来的。所以每次进行跨域请求时，服务器都认为不是同一个浏览器所发起的请求，session也会不一样。以下将介绍如何解决跨域及session共享

1、后台构建一个拦截器，对需要跨域访问的request头部重写，解决跨域

  a)、增加拦截器，代码如下

package com.hnac.hzinfo.common.utils;
 
import org.springframework.stereotype.Component;
 
import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
 
/**
 * CorsFileter 功能描述：CORS过滤器
 */
@Component
public class CorsFilter 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;
        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");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        filterChain.doFilter(servletRequest, servletResponse);
    }
 
    @Override
    public void destroy() {
 
    }
}

  b)、web.xml中增加如下配置

<filter>
	<filter-name>cors</filter-name>
	<filter-class>com.hnac.hzinfo.common.utils.CorsFilter</filter-class>
</filter>
<filter-mapping>
	<filter-name>cors</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>

2、前端Ajax请求，解决session共享

$.ajax({
    url:url,
    <! -- 加上此部分 Start-- >
    xhrFields: {
       withCredentials: true
    },
    crossDomain: true,
    <! -- 加上此部分 End-- >
    success:function() {
    },
    error:function() {
    }
});