java后台设置可跨域访问，前端ajax获取json数据，解决浏览器限制跨域访问的问题

  在本地用ajax跨域访问请求时报错：javascript XMLHttpRequest cannot loadhttp://xxx/. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.html  

>>阅读原文<<