(十一)：ES的编程操作

1、ES API的两种方式

　　Elasticsearch 的API 分为 REST Client API（http请求形式）以及 transportClientAPI两种。相比来说transportClient API效率更高，transportClient是通过Elasticsearch内部RPC的形式进行请求的，连接可以是一个长连接，相当于是把客户端的请求当成Elasticsearch 集群的一个节点， REST Client API 也支持httpd的keepAlive形式的长连接，只是非内部RPC形式。

　　Elasticsearch 7 后就会移除transportClient，主要原因是transportClient 难以向下兼容版本。

1.1 9300[TCP]

  利用9300端口的是spring-data-elasticsearch:transport-api.jar,但是这种方式因为对应的SpringBoot版本不一致，造成对应的transport-api.jar也不同，不能适配es的版本，而且ElasticSearch7.x中已经不推荐使用了，ElasticSearch 8之后更是废弃。

1.2 9200[HTTP]

  基于9200端口的方式也有多种，详情如下：

JsetClient	非官方，更新缓慢
RestTemplate	模拟发送Http请求，ES很多的操作需要我们自己来封装，效率低
HttpClient	与RestTemplate的情况一样
ElasticSearch-Rest-Client	官方的RestClient，封装了ES的操作，API层次分明，易于上手
JavaAPIClient	7.15版本后推荐

　　下面重点来看ElasticSearch-Rest-Client的构建。

2、ElasticSearch-Rest-Client的应用

2.1、添加依赖

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>2.4.12</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <version>2.4.12</version>
    </dependency>
    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-high-level-client</artifactId>
        <version>7.4.2</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>RELEASE</version>
        <scope>test</scope>
    </dependency>
</dependencies>

2.2、添加ES配置

2.2.1、ES客户端配置

　　文档：https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high-getting-started-initialization.html。

 　　客户端配置如下：

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @Description: ElasticSearch的配置类
 * @author: snails
 */
@Configuration
public class ElasticSearchConfiguration {

    @Bean
    public RestHighLevelClient restHighLevelClient() {
        // 构建ES客户端
        RestClientBuilder builder = RestClient.builder(new HttpHost("127.0.0.1", 9200, "http"));
        RestHighLevelClient client = new RestHighLevelClient(builder);
        return client;
    }
}

　　测试从Spring容器中获取client对象：

import org.elasticsearch.client.RestHighLevelClient;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

/**
 * @Description:
 * @author: snails
 */
@SpringBootTest
public class ESApplicationTests {

    @Autowired
    private RestHighLevelClient client;

    @Test
    public void contextLoads() {
        System.out.println("====> " + client);
    }
}

　　输出结果不为空，表示连接ES服务成功。

2.2.2、设置RequestOptions

　　文档：https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/7.17/java-rest-low-usage-requests.html#java-rest-low-usage-request-options。

　　在 ElasticSearchConfiguration 中添加如下内容：

private static final RequestOptions COMMON_OPTIONS;
static {
    RequestOptions.Builder builder = RequestOptions.DEFAULT.toBuilder();
    COMMON_OPTIONS = builder.build();
}

2.3、API使用

2.3.1、保存文档

@Test
public void addDocument() throws IOException {
    // 创建索引对象
    IndexRequest indexRequest = new IndexRequest("java_api");
    // 设置id
    indexRequest.id("1");
    // 创建文档对象
    Student stu = new Student();
    stu.setStuno("20130911");
    stu.setAge(15);
    stu.setName("张三");
    // 用Jackson中的对象转json数据
    ObjectMapper objectMapper = new ObjectMapper();
    String json = objectMapper.writeValueAsString(stu);
    indexRequest.source(json, XContentType.JSON);
    // 执行操作
    IndexResponse index = client.index(indexRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 提取返回信息
    System.out.println(index);
}

@Data
class Student{
    private String stuno;
    private String name;
    private Integer age;
}

　　执行结果如下：

　　kibana查询结果如下：

2.3.2、检索文档

2.1、检索出items索引的所有文件

@Test
public void testSearchIndexAllDoc() throws IOException {
    // 1.创建一个 SearchRequest 对象
    SearchRequest searchRequest = new SearchRequest();
    // 设置检索数据对应的索引库
    searchRequest.indices("items");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    searchRequest.source(sourceBuilder);
    // 2.执行检索操作
    SearchResponse response = client.search(searchRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 3.获取检索后的响应对象，解析出需要的数据
    System.out.println("ElasticSearch检索的信息："+response);
}

　　执行结果如下：

2.2、根据address全文检索

@Test
void searchIndexByAddress() throws IOException {
    // 1.创建一个 SearchRequest 对象
    SearchRequest searchRequest = new SearchRequest();
    // 设置检索数据对应的索引库
    searchRequest.indices("items");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    // 查询出items下 address 中包含 586 的记录
    sourceBuilder.query(QueryBuilders.matchQuery("address","586"));
    searchRequest.source(sourceBuilder);

    // 2.执行检索操作
    SearchResponse response = client.search(searchRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 3.获取检索后的响应对象解析出需要的数据
    System.out.println("ElasticSearch检索的信息："+response);
}

　　执行结果如下：

2.3、嵌套的聚合操作：检索出 items 下的年龄分布和每个年龄段的平均薪资

/**
 * 聚合：嵌套聚合
 * @throws IOException
 */
@Test
void searchIndexAggregation() throws IOException {
    // 1.创建一个 SearchRequest 对象
    SearchRequest searchRequest = new SearchRequest();
    // 设置检索数据对应的索引库
    searchRequest.indices("items");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    // 查询出items下 所有的文档
    sourceBuilder.query(QueryBuilders.matchAllQuery());
    // 聚合 aggregation
    // 聚合item下年龄的分布和每个年龄段的平均薪资
    AggregationBuilder aggregationBuiler = AggregationBuilders.terms("ageAgg")
            .field("age")
            .size(2);
    // 嵌套聚合
    aggregationBuiler.subAggregation(AggregationBuilders.avg("balanceAvg").field("balance"));

    sourceBuilder.aggregation(aggregationBuiler);
    // 聚合时，不显示满足条件的文档内容
    sourceBuilder.size(0);
    searchRequest.source(sourceBuilder);
    System.out.println(sourceBuilder);

    // 2.执行检索操作
    SearchResponse response = client.search(searchRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 3.获取检索后的响应对象解析出需要的数据
    System.out.println(response);
}

　　执行结果如下：

2.4、并行的聚合操作：查询出items下年龄段的分布和总的平均薪资

/**
 * 聚合
 * @throws IOException
 */
@Test
void searchIndexAggregation02() throws IOException {
    // 1.创建一个 SearchRequest 对象
    SearchRequest searchRequest = new SearchRequest();
    // 设置检索数据对应的索引库
    searchRequest.indices("items");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    // 查询出items下 所有的文档
    sourceBuilder.query(QueryBuilders.matchAllQuery());
    // 聚合 aggregation
    // 聚合items下年龄的分布和平均薪资
    AggregationBuilder aggregationBuiler = AggregationBuilders.terms("ageAgg")
            .field("age")
            .size(2);

    sourceBuilder.aggregation(aggregationBuiler);
    // 聚合平均年龄
    AvgAggregationBuilder balanceAggBuilder = AggregationBuilders.avg("balanceAgg").field("age");
    sourceBuilder.aggregation(balanceAggBuilder);
    // 聚合时，不显示满足条件的文档内容
    sourceBuilder.size(0);
    searchRequest.source(sourceBuilder);
    System.out.println(sourceBuilder);

    // 2.执行检索操作
    SearchResponse response = client.search(searchRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 3.获取检索后的响应对象解析出需要的数据
    System.out.println(response);
}

　　执行结果如下：

2.5、处理检索后的结果

@Test
void searchIndexResponse() throws IOException {
    // 1.创建一个 SearchRequest 对象
    SearchRequest searchRequest = new SearchRequest();
    // 设置检索数据对应的索引库
    searchRequest.indices("items");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    // 查询出bank下 address 中包含 586 的记录
    sourceBuilder.query(QueryBuilders.matchQuery("address","586"));
    searchRequest.source(sourceBuilder);

    // 2.执行检索操作
    SearchResponse response = client.search(searchRequest, ElasticSearchConfiguration.COMMON_OPTIONS);
    // 3.解析数据
    RestStatus status = response.status();
    TimeValue took = response.getTook();
    SearchHits hits = response.getHits();
    TotalHits totalHits = hits.getTotalHits();
    TotalHits.Relation relation = totalHits.relation;
    long value = totalHits.value;
    // 相关性的最高分
    float maxScore = hits.getMaxScore();
    SearchHit[] hits1 = hits.getHits();
    for (SearchHit documentFields : hits1) {
        String json = documentFields.getSourceAsString();
        // JSON字符串转换为 Object对象
        ObjectMapper mapper = new ObjectMapper();
        Item item = mapper.readValue(json, Item.class);
        System.out.println("item = " + item);
    }
}

@ToString
@Data
static class Item {

    private int account_number;
    private int balance;
    private String firstname;
    private String lastname;
    private int age;
    private String gender;
    private String address;
    private String employer;
    private String email;
    private String city;
    private String state;

}

　　执行结果如下：