[微服务]分布式搜索Java客户端

快速入门

使用RestClient客户端进行数据搜索可以分为两步

1. 构建并发起请求

代码解读：

• 第一步，创建SearchRequest对象，指定索引库名
• 第二步，利用request.source()构建DSL，DSL中可以包含查询、分页、排序、高亮等

• • query()：代表查询条件，利用QueryBuilders.matchAllQuery()构建一个match_all查询的DSL

• 第三步，利用client.search()发送请求，得到响应

核心步骤:

• 这里关键的API有两个，一个是request.source()，它构建的就是DSL中的完整JSON参数。其中包含了query、sort、from、size、highlight等所有功能：

• 另一个是QueryBuilders，其中包含了我们学习过的各种叶子查询、复合查询等：

1. 解析查询结果

elasticsearch返回的结果是一个JSON字符串，结构包含：

• hits：命中的结果

• • total：总条数，其中的value是具体的总条数值
  • max_score：所有结果中得分最高的文档的相关性算分
  • hits：搜索结果的文档数组，其中的每个文档都是一个json对象

• • • _source：文档中的原始数据，也是json对象

因此，我们解析响应结果，就是逐层解析JSON字符串，流程如下：

• SearchHits：通过response.getHits()获取，就是JSON中的最外层的hits，代表命中的结果

• • SearchHits#getTotalHits().value：获取总条数信息
  • SearchHits#getHits()：获取SearchHit数组，也就是文档数组

• • • SearchHit#getSourceAsString()：获取文档结果中的_source，也就是原始的json文档数据

示例

1. 新建测试类

public class ElasticSearchTest {private RestHighLevelClient client;@Testvoid test() {System.out.println("client =" + client);}@BeforeEachvoid setup() {client = new RestHighLevelClient(RestClient.builder(HttpHost.create("http://192.168.1.97:9200")));}@AfterEachvoid tearDown() throws IOException {if (client != null) {client.close();}}
}

1. 创建并发送请求, 解析结果

public class ElasticSearchTest {private RestHighLevelClient client;@Testvoid test() {System.out.println("client =" + client);}@Testvoid testMatchAll() throws IOException {//1.创建request对象SearchRequest request = new SearchRequest("items");//2.配置request参数request.source().query(QueryBuilders.matchAllQuery());//3.发送请求SearchResponse response = client.search(request, RequestOptions.DEFAULT);System.out.println("response = " + response);//4.解析结果SearchHits searchHits = response.getHits();// 总条数long total = searchHits.getTotalHits().value;System.out.println("total = " + total);// 命中的数据SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {// 获取source结果String json = hit.getSourceAsString();// 转为ItemDocItemDoc doc = JSONUtil.toBean(json, ItemDoc.class);System.out.println("doc = " + doc);}}@BeforeEachvoid setup() {client = new RestHighLevelClient(RestClient.builder(HttpHost.create("http://192.168.1.97:9200")));}@AfterEachvoid tearDown() throws IOException {if (client != null) {client.close();}}
}

1. 执行结果

构建查询条件

全文检索的查询条件构造API如下

精确查询的查询条件构造API如下:

布尔查询的查询条件构造API如下:

构建复杂查询条件的搜索

需求: 利用lavaRestClient实现搜索功能, 条件如下

1. 搜索关键字为脱脂牛奶
2. 品牌必须为德亚
3. 价格必须低于300

public class ElasticSearchTest {private RestHighLevelClient client;@Testvoid test() {System.out.println("client =" + client);}@Testvoid testSearch() throws IOException {//1.创建request对象SearchRequest request = new SearchRequest("items");//2.组织DSL参数request.source().query(QueryBuilders.boolQuery().must(QueryBuilders.matchQuery("name", "脱脂牛奶")).filter(QueryBuilders.termQuery("brand", "德亚")).filter(QueryBuilders.rangeQuery("price").lt(3000)));//3.发送请求SearchResponse response = client.search(request, RequestOptions.DEFAULT);System.out.println("response = " + response);//4.解析结果parseResponseResult(response);}private void parseResponseResult(SearchResponse response) {//4.解析结果SearchHits searchHits = response.getHits();// 总条数long total = searchHits.getTotalHits().value;System.out.println("total = " + total);// 命中的数据SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {// 获取source结果String json = hit.getSourceAsString();// 转为ItemDocItemDoc doc = JSONUtil.toBean(json, ItemDoc.class);System.out.println("doc = " + doc);}}@BeforeEachvoid setup() {client = new RestHighLevelClient(RestClient.builder(HttpHost.create("http://192.168.1.97:9200")));}@AfterEachvoid tearDown() throws IOException {if (client != null) {client.close();}}
}

排序和分页

与query类似，排序和分页参数都是基于request.source()来设置:

public class ElasticSearchTest {private RestHighLevelClient client;@Testvoid test() {System.out.println("client =" + client);}@Testvoid testSortAndPage() throws IOException {// 模拟前端分页参数int pageNo = 1, pageSize = 5;//1.创建request对象SearchRequest request = new SearchRequest("items");//2.组织DSL条件//2.1query条件request.source().query(QueryBuilders.matchAllQuery());//2.2.分页条件request.source().from((pageNo - 1) * pageSize).size(pageSize);//2.3 排序条件request.source().sort("sold", SortOrder.DESC).sort("price",SortOrder.ASC);//3.发送请求SearchResponse response = client.search(request, RequestOptions.DEFAULT);//4.解析结果parseResponseResult(response);}private void parseResponseResult(SearchResponse response) {//4.解析结果SearchHits searchHits = response.getHits();// 总条数long total = searchHits.getTotalHits().value;System.out.println("total = " + total);// 命中的数据SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {// 获取source结果String json = hit.getSourceAsString();// 转为ItemDocItemDoc doc = JSONUtil.toBean(json, ItemDoc.class);System.out.println("doc = " + doc);}}@BeforeEachvoid setup() {client = new RestHighLevelClient(RestClient.builder(HttpHost.create("http://192.168.1.97:9200")));}@AfterEachvoid tearDown() throws IOException {if (client != null) {client.close();}}
}

高亮展示

高亮显示的条件构造API如下

高亮显示的结果解析API如下:

示例

public class ElasticSearchTest {private RestHighLevelClient client;@Testvoid test() {System.out.println("client =" + client);}@Testvoid testHighLight() throws IOException {//1.创建request对象SearchRequest request = new SearchRequest("items");//2.组织DSL条件//2.1query条件request.source().query(QueryBuilders.matchQuery("name", "脱脂牛奶"));//2.2.高亮条件request.source().highlighter(SearchSourceBuilder.highlight().field("name"));//3.发送请求SearchResponse response = client.search(request, RequestOptions.DEFAULT);//4.解析结果parseResponseResult(response);}private void parseResponseResult(SearchResponse response) {//4.解析结果SearchHits searchHits = response.getHits();// 总条数long total = searchHits.getTotalHits().value;System.out.println("total = " + total);// 命中的数据SearchHit[] hits = searchHits.getHits();for (SearchHit hit : hits) {// 获取source结果String json = hit.getSourceAsString();// 转为ItemDocItemDoc doc = JSONUtil.toBean(json, ItemDoc.class);// 按需处理高亮结果Map<String, HighlightField> hfs = hit.getHighlightFields();if (hfs != null && !hfs.isEmpty()) {// 根据高亮字段名获取高亮结果HighlightField hf = hfs.get("name");// 获取高亮结果, 覆盖非高亮结果String name = hf.fragments()[0].string();doc.setName(name);}System.out.println("doc = " + doc);}}@BeforeEachvoid setup() {client = new RestHighLevelClient(RestClient.builder(HttpHost.create("http://192.168.1.97:9200")));}@AfterEachvoid tearDown() throws IOException {if (client != null) {client.close();}}
}