当一个请求url的协议、域名、端口三者之间任意一与当前页面地址不同即为跨域，出现跨域问题时，会遇到No ‘Access-Control-Allow-Origin‘ header is present on the requested resource错误
基于CORSFilter可以解决跨域问题，具体代码如下：
public class CORSFilter implements Filter { private FilterConfig filterConfig; @Override public void destroy() { } @Override public void doFilter(ServletRequest srequest, ServletResponse sresponse, FilterChain chain) throws IOException, ServletException { HttpServletResponse response = (HttpServletResponse) sresponse; response.addHeader("Access-Control-Allow-Origin", "*"); response.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE,OPTIONS"); response.addHeader("Access-Control-Allow-Headers", "Content-Type, x-requested-with, X-Custom-Header"); response.addHeader("Access-Control-Max-Age", "1800");// 30 min chain.doFilter(srequest, sresponse); } @Override public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig; } }
添加filter配置
<filter>
<filter-name>CORS</filter-name>
<filter-class>com.zhougl.filter.CORSFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CORS</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
也可以在浏览器的快捷方式中添加--args --disable-web-security --user-data-dir配置解决客户端的跨域问题(不安全，不推荐，临时使用)
如果是flash的跨域，则需要在被访问端添加crossdomain.xml，代码示例如下：
<cross-domain-policy> <site-control permitted-cross-domain-policies="all"/> <allow-access-from domain="*"/> <allow-http-request-headers-from domain="*" headers="*"/> </cross-domain-policy>
关于crossdomain.xml的具体文档参考：
https://www.adobe.com/devnet/articles/crossdomain_policy_file_spec.html
crossdomain.xml的存放有两种方式：
1、存放在域名的根目录下，比如https://www.taobao.com/crossdomain.xml
2、如果不存在根目录下，而是具体的某个web项目下，则需要在flash的as脚本中加载配置
Security.loadPolicyFile("http://ip:port/webappname/crossdomain.xml");
原文：https://www.cnblogs.com/yytxdy/p/12341897.html