以下是一个简单的Maven工程和Spring demo案例，演示如何使用Java调用Elasticsearch。

配置Maven依赖

在pom.xml文件中添加以下依赖：

org.elasticsearch elasticsearch 6.5.4 org.elasticsearch.client transport 6.5.4 org.elasticsearch.client rest 6.5.4

创建Elasticsearch连接

创建一个Elasticsearch连接配置类，用于连接Elasticsearch集群。示例代码如下：

@Configuration
public class ElasticsearchConfig {

private static final String HOST = "localhost";
private static final int PORT = 9300;

@Bean
public RestHighLevelClient restHighLevelClient() {
    RestClientBuilder builder = RestClient.builder(new HttpHost(HOST, PORT));
    RestHighLevelClient client = new RestHighLevelClient(builder);
    return client;
}

}

创建Elasticsearch操作类

创建一个Elasticsearch操作类，用于执行Elasticsearch的操作。示例代码如下：

@Component

public class ElasticsearchService {


private RestHighLevelClient client;

@Autowired
public ElasticsearchService(RestHighLevelClient client) {
    this.client = client;
}

public void createIndex(String indexName) throws IOException {
    CreateIndexRequest request = new CreateIndexRequest(indexName);
    client.indices().create(request, RequestOptions.DEFAULT);
}

public void deleteIndex(String indexName) throws IOException {
    DeleteIndexRequest request = new DeleteIndexRequest(indexName);
    client.indices().delete(request, RequestOptions.DEFAULT);
}

public void insert(String indexName, String id, String jsonString) throws IOException {
    IndexRequest request = new IndexRequest(indexName);
    request.id(id);
    request.source(jsonString, XContentType.JSON);
    IndexResponse response = client.index(request, RequestOptions.DEFAULT);
}

public void update(String indexName, String id, String jsonString) throws IOException {
UpdateRequest request = new UpdateRequest(indexName, id);

        request.doc(jsonString, XContentType.JSON);

        UpdateResponse response = client.update(request, RequestOptions.DEFAULT);

    }


public void delete(String indexName, String id) throws IOException {
    DeleteRequest request = new DeleteRequest(indexName, id);
    DeleteResponse response = client.delete(request, RequestOptions.DEFAULT);
}

public SearchHits search(String indexName, QueryBuilder queryBuilder) throws IOException {
    SearchRequest searchRequest = new SearchRequest(indexName);
    SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
    searchSourceBuilder.query(queryBuilder);
    searchRequest.source(searchSourceBuilder);
    SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);
    SearchHits hits = response.getHits();
    return hits;
}

}


4. 创建Spring Boot控制器

创建一个Spring Boot控制器，在其中调用Elasticsearch操作类执行Elasticsearch操作。示例代码如下：

@RestController

public class ElasticsearchController {


@Autowired
private ElasticsearchService elasticsearchService;

@GetMapping("/createIndex")
public String createIndex() throws IOException {
    elasticsearchService.createIndex("my_index");
    return "Index created successfully";
}

@GetMapping("/deleteIndex")
public String deleteIndex() throws IOException {
    elasticsearchService.deleteIndex("my_index");
    return "Index deleted successfully";
}

@PostMapping("/insert")
public String insert() throws IOException {
    String jsonString = "{\"title\":\"Java Programming\",\"author\":\"John Doe\"}";
    elasticsearchService.insert("my_index", "1", jsonString);
    return "Document inserted successfully";
}

@PostMapping("/update")
public String update() throws IOException {
    String jsonString = "{\"title\":\"Java Programming\",\"author\":\"Jane Doe\"}";
    elasticsearchService.update("my_index", "1", jsonString);
    return "Document updated successfully";
}

@GetMapping("/delete")
public String delete() throws IOException {
    elasticsearchService.delete("my_index", "1");
    return "Document deleted successfully";
}

@GetMapping("/search")
public SearchHits search() throws IOException {
    QueryBuilder queryBuilder = QueryBuilders.matchQuery("title", "Java");
    SearchHits hits = elasticsearchService.search("my_index", queryBuilder);
    return hits;
}

}

以上代码演示了如何创建Elasticsearch连接、执行Elasticsearch

操作，以及在Spring Boot控制器中调用Elasticsearch操作类执行操作。

测试

运行Spring Boot应用程序，并访问以下URL以执行相应的操作：

/createIndex：创建名为“my_index”的索引。

/deleteIndex：删除名为“my_index”的索引。

/insert：向名为“my_index”的索引插入一条文档。

/update：更新名为“my_index”的索引中的文档。

/delete：从名为“my_index”的索引中删除文档。

/search：从名为“my_index”的索引中搜索匹配“Java”的文档。

可以使用Postman或类似的工具进行测试。

以上就是一个基本的Maven工程和Spring demo案例，演示了如何使用Java调用Elasticsearch。这只是一个简单的示例，实际应用中可能需要更复杂和细致的实现。