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：

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：

@Componentpublic 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：@RestControllerpublic 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。