前后端分离，跨域问题

前后端分离，跨域问题，添加一个跨域的过滤器
添加JWT的时候，需要再headers里面带token和token-type，那么在CORSFilter 里面需要加上对应的response.setHeader里面添加对应的名字，如Authorization（登录返回的token）和token-type（登录返回的token_type）

在web.xml中添加过滤器：

<filter>
      <filter-name>cors</filter-name>
      <filter-class>com.mdl.core.filter.CORSFilter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>cors</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>

package com.mdl.core.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;
@Component
public class CORSFilter implements Filter{

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        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", "Origin, X-Requested-With, Content-Type, token-type, Accept,Authorization");

       /* if ("OPTIONS".equals(request.method, ignoreCase = true)) {
            response.status = HttpServletResponse.SC_OK;
        } else {
            chain.doFilter(req, res);
        }*/


        chain.doFilter(req, res);
    }
    public void init(FilterConfig filterConfig) {}
    public void destroy() {}
}