解决方法安装Solr过程出现错误，报异常
org.apache.solr.common.SolrException: Error loading class 'solr.VelocityResponseWriter' ，
解决方法：
找到$solr_home\conf\solrconfig.xml，把中间(Solr 3.5.0 1554行)
<queryResponseWriter name="velocity" class="solr.VelocityResponseWriter" enable="${solr.velocity.enabled:true}"/>注释或者disabled - enable:false即可。
在本段之前，solrconfig.xml中就有写：
- <!--
- Custom response writers can be declared as needed...
- -->
- <!-- The solr.velocity.enabled flag is used by Solr's test cases so that this response writer is not
- loaded (causing an error if contrib/velocity has not been built fully) -->
- <queryResponseWriter name="velocity" class="solr.VelocityResponseWriter" enable="${solr.velocity.enabled:false}"/>
