這段日子在搞 springdata 操作 elasticsearch 其中使用聚合操作，特此一記：

下面是https://github.com/spring-projects/spring-data-elasticsearch/tree/5.x 的spring-data-elasticsearch 項目的：ElasticsearchTemplateAggregationTests代碼：

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration("classpath:elasticsearch-template-test.xml") public class ElasticsearchTemplateAggregationTests {public static final String RIZWAN_IDREES = "Rizwan Idrees";public static final String MOHSIN_HUSEN = "Mohsin Husen";public static final String JONATHAN_YAN = "Jonathan Yan";public static final String ARTUR_KONCZAK = "Artur Konczak";public static final int YEAR_2002 = 2002;public static final int YEAR_2001 = 2001;public static final int YEAR_2000 = 2000;@Autowiredprivate ElasticsearchTemplate elasticsearchTemplate;@Beforepublic void before() {elasticsearchTemplate.deleteIndex(ArticleEntity.class);elasticsearchTemplate.createIndex(ArticleEntity.class);elasticsearchTemplate.putMapping(ArticleEntity.class);elasticsearchTemplate.refresh(ArticleEntity.class);IndexQuery article1 = new ArticleEntityBuilder("1").title("article four").subject("computing").addAuthor(RIZWAN_IDREES).addAuthor(ARTUR_KONCZAK).addAuthor(MOHSIN_HUSEN).addAuthor(JONATHAN_YAN).score(10).buildIndex();IndexQuery article2 = new ArticleEntityBuilder("2").title("article three").subject("computing").addAuthor(RIZWAN_IDREES).addAuthor(ARTUR_KONCZAK).addAuthor(MOHSIN_HUSEN).addPublishedYear(YEAR_2000).score(20).buildIndex();IndexQuery article3 = new ArticleEntityBuilder("3").title("article two").subject("computing").addAuthor(RIZWAN_IDREES).addAuthor(ARTUR_KONCZAK).addPublishedYear(YEAR_2001).addPublishedYear(YEAR_2000).score(30).buildIndex();IndexQuery article4 = new ArticleEntityBuilder("4").title("article one").subject("accounting").addAuthor(RIZWAN_IDREES).addPublishedYear(YEAR_2002).addPublishedYear(YEAR_2001).addPublishedYear(YEAR_2000).score(40).buildIndex();elasticsearchTemplate.index(article1);elasticsearchTemplate.index(article2);elasticsearchTemplate.index(article3);elasticsearchTemplate.index(article4);elasticsearchTemplate.refresh(ArticleEntity.class);}@Testpublic void shouldReturnAggregatedResponseForGivenSearchQuery() {// givenSearchQuery searchQuery = new NativeSearchQueryBuilder().withQuery(matchAllQuery()).withSearchType(SearchType.DEFAULT).withIndices("test-index-articles").withTypes("article").addAggregation(terms("subjects").field("subject")).build();// whenAggregations aggregations = elasticsearchTemplate.query(searchQuery, new ResultsExtractor<Aggregations>() {@Overridepublic Aggregations extract(SearchResponse response) {return response.getAggregations();}});// // Aggregations 只是獲得了結果，沒有取出數據；以及這樣的實例；assertThat(aggregations, is(notNullValue())); assertThat(aggregations.asMap().get("subjects"), is(notNullValue()));}}

其實上面代碼使用 restful 方式的拼寫為：

GET test-index-articles/article/_search {"size": 0, "aggs": {"my_aggs_hehe": {"terms": {"field": "subject"}}} }以及返回的結果：

{"took": 231,"timed_out": false,"_shards": {"total": 1,"successful": 1,"failed": 0},"hits": {"total": 4,"max_score": 0,"hits": []},"aggregations": {"my_aggs_hehe": {"doc_count_error_upper_bound": 0,"sum_other_doc_count": 0,"buckets": [{"key": "computing","doc_count": 3},{"key": "accounting","doc_count": 1}]}} }

那么我經過使用 java 的 debug 模式查看生成的類：

于是我將代碼寫如下：

@Testpublic void shouldReturnAggregatedResponseForGivenSearchQuery() {// givenSearchQuery searchQuery = new NativeSearchQueryBuilder().withQuery(matchAllQuery()).withSearchType(SearchType.DEFAULT).withIndices("test-index-articles").withTypes("article").addAggregation(terms("subjects").field("subject")).build();// whenAggregations aggregations = elasticsearchTemplate.query(searchQuery, new ResultsExtractor<Aggregations>() {@Overridepublic Aggregations extract(SearchResponse response) {return response.getAggregations();}});Map<String, Aggregation> map=aggregations.asMap();for(String s:map.keySet()){StringTerms a=(StringTerms) map.get(s);List<Terms.Bucket> list=a.getBuckets();for(Terms.Bucket b:list){System.out.println("key is "+ b.getKeyAsString()+"---and value is "+ b.getDocCount());}}// thenassertThat(aggregations, is(notNullValue()));assertThat(aggregations.asMap().get("subjects"), is(notNullValue()));}
于是結果為：

key is computing---and value is 3 key is accounting---and value is 1

總結

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