Enable CORS in Apache Solr
Quick post since there's no easy googlable (?) resource to do this.
open the file server/solr-webapp/webapp/WEB-INF/web.xml and add the following XML before the existing filter section:
<filter>
<filter-name>cross-origin</filter-name>
<filter-class>org.eclipse.jetty.servlets.CrossOriginFilter</filter-class>
<init-param>
<param-name>allowedOrigins</param-name>
<param-value>http://localhost*</param-value>
</init-param>
<init-param>
<param-name>allowedMethods</param-name>
<param-value>GET,POST,DELETE,PUT,HEAD,OPTIONS</param-value>
</init-param>
<init-param>
<param-name>allowedHeaders</param-name>
<param-value>origin, content-type, cache-control, accept, options, authorization, x-requested-with</param-value>
</init-param>
<init-param>
<param-name>supportsCredentials</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>chainPreflight</param-name>
<param-value>false</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>cross-origin</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
taken from this Stack Overflow response