05-ES的RestClient(操作索引库)

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

其中的Java Rest Client又包括两种：

Java Low Level Rest ClientJava High Level Rest Client

这里使用的是Java HighLevel Rest Client

CREATE TABLE `tb_hotel` (
  `id` bigint(20) NOT NULL COMMENT '酒店id',
  `name` varchar(255) NOT NULL COMMENT '酒店名称；例：7天酒店',
  `address` varchar(255) NOT NULL COMMENT '酒店地址；例：航头路',
  `price` int(10) NOT NULL COMMENT '酒店价格；例：329',
  `score` int(2) NOT NULL COMMENT '酒店评分；例：45，就是4.5分',
  `brand` varchar(32) NOT NULL COMMENT '酒店品牌；例：如家',
  `city` varchar(32) NOT NULL COMMENT '所在城市；例：上海',
  `star_name` varchar(16) DEFAULT NULL COMMENT '酒店星级，从低到高分别是：1星到5星，1钻到5钻',
  `business` varchar(255) DEFAULT NULL COMMENT '商圈；例：虹桥',
  `latitude` varchar(32) NOT NULL COMMENT '纬度；例：31.2497',
  `longitude` varchar(32) NOT NULL COMMENT '经度；例：120.3925',
  `pic` varchar(255) DEFAULT NULL COMMENT '酒店图片；例:/img/1.jpg',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

ES中支持两种地理坐标数据类型：

geo_point：由纬度（latitude）和经度（longitude）确定的一个点。例如：“32.8752345, 120.2981576”geo_shape：有多个geo_point组成的复杂几何图形。例如一条直线，“LINESTRING (-77.03653 38.897676, -77.009051 38.889939)”

字段拷贝可以使用copy_to属性将当前字段拷贝到指定字段,实现根据一个字段搜索多个字段的效果。

PUT /hotel
{
  "mappings": {
    "properties": {
      "id":{
        "type": "keyword"
      },
      "name":{
        "type": "text",
        "analyzer": "ik_max_word",
        "copy_to":"all"
      },
      "address":{
        "type": "keyword",
        "index": false
      },
      "price":{
        "type": "integer"
      },
      "score":{
        "type": "integer"
      },
      "brand":{
        "type": "keyword",
        "copy_to":"all"
      },
      "city":{
        "type": "keyword"
      },
      "starName":{
        "type": "keyword"
      },
      "business":{
        "type": "keyword",
        "copy_to":"all"
      },
      "location":{
        "type": "geo_point"
      },
      "pic":{
        "type": "keyword",
        "index": false
      },
      "all":{
        "type": "text",
        "analyzer": "ik_max_word"
      }
    }
  }
}

几个特殊字段说明：

location：地理坐标，里面包含精度、纬度all：一个组合字段，其目的是将多字段的值 利用copy_to合并，提供给用户搜索 初始化RestClient

在elasticsearch提供的API中，与elasticsearch一切交互都封装在一个名为RestHighLevelClient的类中，必须先完成这个对象的初始化，建立与elasticsearch的连接。

    org.elasticsearch.client
    elasticsearch-rest-high-level-client

因为SpringBoot默认的ES版本是7.6.2，所以我们需要覆盖默认的ES版本

        1.8
        7.12.1
    

RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(
        HttpHost.create("http://192.168.116.131:9200")
));

创建一个测试类HotelIndexTest，然后将初始化的代码编写在@BeforeEach方法中：

public class HotelIndexTest {
    private RestHighLevelClient client;

    @BeforeEach
    void setUp() {
        this.client = new RestHighLevelClient(RestClient.builder(
                HttpHost.create("http://192.168.116.131:9200")
        ));
    }

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

代码分为三步：

1）创建Request对象。因为是创建索引库的操作，因此Request是CreateIndexRequest。2）添加请求参数，其实就是DSL的JSON参数部分。因为json字符串很长，这里是定义了静态字符串常量MAPPING_TEMPLATE，让代码看起来更加优雅。3）发送请求，client.indices()方法的返回值是IndicesClient类型，封装了所有与索引库操作有关的方法。 定义mapping映射的JSON字符串常量

package cn.bttc.hotel.constants;

public class HotelIndexConstants {
    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": falsen" +
            "      },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" +
            "      "pic": {n" +
            "        "type": "keyword",n" +
            "        "index": falsen" +
            "      },n" +
            "      "location": {n" +
            "        "type": "geo_point"n" +
            "      },n" +
            "      "all": {n" +
            "        "type": "text",n" +
            "        "analyzer": "ik_max_word"n" +
            "      }n" +
            "    }n" +
            "  }n" +
            "}";
}

@Test
void createHotelIndex() throws IOException {
    // 1.创建Request对象
    CreateIndexRequest request = new CreateIndexRequest("hotel");
    // 2.准备请求的参数：DSL语句
    request.source(MAPPING_TEMPLATE, XContentType.JSON);
    // 3.发送请求
    client.indices().create(request, RequestOptions.DEFAULT);
}

@Test
void testDeleteHotelIndex() throws IOException {
    // 1.创建Request对象
    DeleteIndexRequest request = new DeleteIndexRequest("hotel");
    // 2.发送请求
    client.indices().delete(request, RequestOptions.DEFAULT);
}

@Test
void testExistsHotelIndex() throws IOException {
    // 1.创建Request对象
    GetIndexRequest request = new GetIndexRequest("hotel");
    // 2.发送请求
    boolean exists = client.indices().exists(request, RequestOptions.DEFAULT);
    // 3.输出
    System.err.println(exists ? "索引库已经存在！" : "索引库不存在！");
}