springboot整合ElasticsearchClient ，实现sql语句查询

要在Spring Boot应用程序中使用ElasticsearchClient进行SQL语句查询，需要以下步骤：

1. 添加ElasticsearchClient和其依赖项的Maven依赖关系：

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-client</artifactId>
    <version>7.9.3</version>
</dependency>
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.9.3</version>
</dependency>

2. 配置ElasticsearchClient连接：

elasticsearch:
  rest:
    hosts: localhost:9200
    scheme: http

3. 创建ElasticsearchClient连接客户端：

import java.util.Collections;
import org.elasticsearch.client.RestHighLevelClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.elasticsearch.RestClientProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.elasticsearch.client.RestClients.ElasticsearchRestClient;
import org.springframework.data.elasticsearch.client.RestClients.ElasticsearchRestClientBuilder;
import org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate;
import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
import org.springframework.data.elasticsearch.core.mapping.SimpleElasticsearchMappingContext;

@Configuration
public class ElasticsearchConfig {
    
    private final RestClientProperties properties;

    @Autowired
    public ElasticsearchConfig(RestClientProperties properties) {
        this.properties = properties;
    }

    @Bean
    public RestHighLevelClient elasticsearchClient() {
        return new ElasticsearchRestClientBuilder(Collections.singletonList(properties.getUris()))
            .withScheme(properties.getScheme())
            .withBasicAuth(properties.getUsername(), properties.getPassword())
            .build();
    }

    @Bean
    public ElasticsearchRestTemplate elasticsearchTemplate(RestHighLevelClient elasticsearchClient,
            ElasticsearchConverter elasticsearchConverter) {
        return new ElasticsearchRestTemplate(new ElasticsearchRestClient(elasticsearchClient), elasticsearchConverter);
    }

    @Bean
    public ElasticsearchConverter elasticsearchConverter() {
        return new ElasticsearchConverter(new SimpleElasticsearchMappingContext());
    }
}

4. 编写SQL查询，例如：

SELECT * FROM my_index WHERE title LIKE '%Spring%';

5. 在Spring Boot应用程序中使用ElasticsearchClient执行SQL查询：

import java.io.IOException;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.core.CountResponse;
import org.elasticsearch.client.core.SearchRequest;
import org.elasticsearch.client.core.SearchResponse;
import org.elasticsearch.client.core.TermVectorsRequest;
import org.elasticsearch.client.core.TermVectorsResponse;
import org.elasticsearch.client.sql.SqlRequest;
import org.elasticsearch.client.sql.SqlResponse;
import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.elasticsearch.client.RestClients.ElasticsearchRestClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ElasticsearchController {

    @Autowired
    private ElasticsearchRestClient elasticsearchClient;

    @GetMapping("/search")
    public void search(@RequestParam("query") String query) throws IOException {
        SqlRequest sqlRequest = new SqlRequest(query);
        SqlResponse sqlResponse = elasticsearchClient.sql().query(sqlRequest).getResponse();
        System.out.println(sqlResponse.toString());
    }
}