ajax同源策略问题

ajax请求时，经常出现跨域问题，解决方案一:

Tomcat-conf/web.xml添加Access-Control-Allow-Origin

 <filter>

  <filter-name>CorsFilter</filter-name>

  <filter-class>org.apache.catalina.filters.CorsFilter</filter-class>

  <init-param>

    <param-name>cors.allowed.methods</param-name>

    <param-value>GET,POST,HEAD,OPTIONS,PUT</param-value>

  </init-param>

  <init-param>

    <param-name>cors.allowed.headers</param-name>

<param-value>Access-Control-Allow-Origin,Content-Type,X-Requested-With,accept,Origin,Access-Control-Request-Method,Access-Control-Request-Headers</param-value>

  </init-param>

  <async-supported>true</async-supported>

</filter>

<filter-mapping>

  <filter-name>CorsFilter</filter-name>

  <url-pattern>/*</url-pattern>

</filter-mapping>