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四、RestAPI

ES官方提供了各种不同语言的客户端，用来操作ES。
这些客户端的本质就是组装DSL语句，通过http请求发送给ES。
官方文档地址：https://www.elastic.co/guide/en/elasticsearch/client/index.html

案例：利用JavaRestClient实现创建、删除索引库，判断索引库是否存在

1. 准备工程
   导入项目
   导入mysql数据
   修改application.yaml中的url和password，改为自己数据库的位置和密码
2. 创建索引库
   导入es依赖

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

更改es版本为我们当前使用的版本

<properties>
	<elasticsearch.version>7.12.1</elasticsearch.version>
</properties>

初始化代码

public class HotelIndexTest {
    private RestHighLevelClient client;

    @BeforeEach
    void setUp() {
        this.client = new RestHighLevelClient(RestClient.builder(
                HttpHost.create("http://192.168.179.128:9200")
        ));
    }

    @AfterEach
    void tearDown() throws IOException {
        this.client.close();
    }
}

建立DSL的JSON参数部分

package cn.itcast.hotel;

public class HotelConstants {
    public static final String MAPPING_TEMPLATE = "{\n" +
            "  \"mappings\": {\n" +
            "    \"properties\": {\n" +
            "      \"id\": {\n" +
            "        \"type\": \"keyword\"\n" +
            "      },\n" +
            "      \"name\": {\n" +
            "        \"type\": \"text\",\n" +
            "        \"analyzer\": \"ik_max_word\",\n" +
            "        \"copy_to\": \"all\"\n" +
            "      },\n" +
            "      \"address\": {\n" +
            "        \"type\": \"keyword\",\n" +
            "        \"index\": false\n" +
            "      },\n" +
            "      \"price\": {\n" +
            "        \"type\": \"integer\"\n" +
            "      },\n" +
            "      \"score\": {\n" +
            "        \"type\": \"integer\"\n" +
            "      },\n" +
            "      \"brand\": {\n" +
            "        \"type\": \"keyword\",\n" +
            "        \"copy_to\": \"all\"\n" +
            "      },\n" +
            "      \"city\": {\n" +
            "        \"type\": \"keyword\"\n" +
            "      },\n" +
            "      \"starName\": {\n" +
            "        \"type\": \"keyword\"\n" +
            "      },\n" +
            "      \"business\": {\n" +
            "        \"type\": \"keyword\",\n" +
            "        \"copy_to\": \"all\"\n" +
            "      },\n" +
            "      \"location\": {\n" +
            "        \"type\": \"geo_point\"\n" +
            "      },\n" +
            "      \"pic\": {\n" +
            "        \"type\": \"keyword\",\n" +
            "        \"index\": false\n" +
            "      },\n" +
            "      \"all\": {\n" +
            "        \"type\": \"text\",\n" +
            "        \"index\": true,\n" +
            "        \"analyzer\": \"ik_max_word\"\n" +
            "      }\n" +
            "    }\n" +
            "  }\n" +
            "}";
}

发送请求

@Test
void testCreateHotelIndex() throws IOException {
    CreateIndexRequest request = new CreateIndexRequest("hotel");
    request.source(MAPPING_TEMPLATE, XContentType.JSON);
    client.indices().create(request, RequestOptions.DEFAULT);
}

3. 删除索引库

@Test
void testDeleteHotelIndex() throws IOException {
    DeleteIndexRequest request = new DeleteIndexRequest("hotel");
    client.indices().delete(request, RequestOptions.DEFAULT);
}

4. 判断索引库是否存在

@Test
void testExitsHotelIndex() throws IOException {
    GetIndexRequest request = new GetIndexRequest("hotel");
    boolean exists = client.indices().exists(request, RequestOptions.DEFAULT);
    System.out.println(exists);
}

总结：

JavaRestClient操作elasticsearch的流程基本类似。
核心是client.indices()方法来获取索引库的操作对象。
索引库操作的基本步骤：
初始化RestHighLevelClient
创建XxxIndexRequest。XXX是Create、Get、Delete
准备DSL（ Create时需要，其它是无参）
发送请求。调用RestHighLevelClient#indices().xxx()方法，xxx是create、exists、delete