现有索引数据：

index:school  type:student  ---------------------------------------------------  {"grade":"1", "class":"1", "name":"xiao 1"}  {"grade":"1", "class":"1", "name":"xiao 2"}  {"grade":"1", "class":"2", "name":"xiao 3"}  {"grade":"1", "class":"2", "name":"xiao 4"}  {"grade":"1", "class":"2", "name":"xiao 5"}

Java分组统计年级和班级学生个数，如SQL: SELECT grade,class,count(1) FROM student GROUP BY grade,class;

package test;    import java.util.Iterator;  import java.util.Map;    import org.elasticsearch.action.search.SearchRequestBuilder;  import org.elasticsearch.action.search.SearchResponse;  import org.elasticsearch.action.search.SearchType;  import org.elasticsearch.search.aggregations.Aggregation;  import org.elasticsearch.search.aggregations.AggregationBuilders;  import org.elasticsearch.search.aggregations.bucket.terms.StringTerms;  import org.elasticsearch.search.aggregations.bucket.terms.Terms.Bucket;  import org.elasticsearch.search.aggregations.bucket.terms.TermsBuilder;  import org.junit.Test;    import utils.NesUtils;    public class TestAggregation  {      @Test      public void testAggregation()      {          SearchRequestBuilder srb = NesUtils.getSearcher("school");          srb.setTypes("student");          srb.setSearchType(SearchType.COUNT);            TermsBuilder gradeTermsBuilder = AggregationBuilders.terms("gradeAgg").field("grade");          TermsBuilder classTermsBuilder = AggregationBuilders.terms("classAgg").field("class");            gradeTermsBuilder.subAggregation(classTermsBuilder);            srb.addAggregation(gradeTermsBuilder);            SearchResponse sr = srb.execute().actionGet();            Map<String, Aggregation> aggMap = sr.getAggregations().asMap();            StringTerms gradeTerms = (StringTerms) aggMap.get("gradeAgg");            Iterator<Bucket> gradeBucketIt = gradeTerms.getBuckets().iterator();            while(gradeBucketIt.hasNext())          {              Bucket gradeBucket = gradeBucketIt.next();              System.out.println(gradeBucket.getKey() + "年级有" + gradeBucket.getDocCount() +"个学生。");                StringTerms classTerms = (StringTerms) gradeBucket.getAggregations().asMap().get("classAgg");              Iterator<Bucket> classBucketIt = classTerms.getBuckets().iterator();                while(classBucketIt.hasNext())              {                  Bucket classBucket = classBucketIt.next();                  System.out.println(gradeBucket.getKey() + "年级" +classBucket.getKey() + "班有" + classBucket.getDocCount() +"个学生。");              }              System.out.println();          }        }  }

运行完成输出结果

---------------------------------------------------  1年级有5个学生。  1年级2班有3个学生。  1年级1班有2个学生。