solr faceting 用法

1.在schema.xml里面增加一个分类字段category
2.创建索引
3.在查询url里面增加：&facet=on&facet.field=category
    查询返回结果里会出现如下返回结果：

<lst name="facet_counts">
<lst name="facet_queries"/>
−
<lst name="facet_fields">
−
<lst name="category">
<int name="java">4</int>
<int name="3c">2</int>
<int name="电脑">2</int>
</lst>
</lst>
<lst name="facet_dates"/>
</lst>

4.用solrJ 的API查询：

/create the query
SolrQuery query = new SolrQuery("content:piece");
//indicate we want facets
query.setFacet(true);
//indicate what field to facet on
query.addFacetField("category");
//we only want facets that have at least one entry
query.setFacetMinCount(1);
//run the query
QueryResponse results = server.query(query);
System.out.println("Query Results: " + results);
//print out the facets
List<FacetField> facets = results.getFacetFields();
for (FacetField facet : facets) {
　System.out.println("Facet:" + facet);
}

具体参考：http://wiki.apache.org/solr/SimpleFacetParameters