当做ssm+vue项目时，往往会遇到跨域的问题，废话不多说，直接上干货。

1. 新建一个Filter，直接new一个Filter（注意）

2.重写里面的doFilter方法即可

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        // TODO Auto-generated method stub
        // place your code here
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse) resp;
        String originHeader = request.getHeader("Origin");
        response.setHeader("Access-Control-Allow-Origin", originHeader);
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Max-Age", "0");
        response.setHeader("Access-Control-Allow-Headers", "Origin, No-Cache, X-Requested-With, If-Modified-Since, Pragma, Last-Modified, Cache-Control, Expires, Content-Type, X-E4M-With,userId,token");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("XDomainRequestAllowed","1");
        response.setHeader("XDomainRequestAllowed","1");
        // pass the request along the filter chain
        chain.doFilter(request, response);
    }

3.在web.xml中加入以下代码：

<!-- 跨域问题解决 -->
    <filter>
        <filter-name>header</filter-name>
        <filter-class>com.ssm.filter.filter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>header</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>