Error starting solr: javax.ws.rs.InternalServerErrorException: HTTP 500 Server Error
Error starting solr: Error while waiting for a response from the agent: javax.ws.rs.InternalServerErrorException: HTTP 500 Server Error.
This error usually occurs when there are some conflicting jars in classpath. Look for any new jar file that you added in solr classpath or the jre (eg. jre/lib/ext folder) and remove them and start solr again.