cors解决跨域问题

前端接口调用不做任何处理，注意请求路径是绝对路径

后端需要在类中添加如下代码：

 // 设置：Access-Control-Allow-Origin头，处理Session问题
        response.setHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("P3P", "CP=CAO PSA OUR");
        if (request.getHeader("Access-Control-Request-Method") != null && "OPTIONS".equals(request.getMethod())) {
            response.addHeader("Access-Control-Allow-Methods", "POST,GET,TRACE,OPTIONS");
            response.addHeader("Access-Control-Allow-Headers", "Content-Type,Origin,Accept");
            response.addHeader("Access-Control-Max-Age", "120");
        }