Elasticsearch Java client使用

前言

Elasticsearch官方列出了好几个客户端，如下所示

Java Client
Java Rest Client（Java High Level REST Client）
Java Transport Client

其中Java Rest Client在7.15.0被标记已过时，Java Transport Client暂时没找到在哪个版本被标记过时

注：

官方文档
Spring Boot 2.3.12.RELEASE
Elasticsearch 7.17.5

Java Client 集成

Java Client在构建对象时支持Build模式以及Lambda两种形式，暴露出来的API为ElasticsearchClient类，通过该类可进行对索引、文档的基本操作。

ElasticsearchClient对象初始化步骤

第一步，引入依赖

<dependency>

    <groupId>co.elastic.clients</groupId>

    <artifactId>elasticsearch-java</artifactId>

    <version>7.17.5</version>

</dependency>

<dependency>

    <groupId>com.fasterxml.jackson.core</groupId>

    <artifactId>jackson-databind</artifactId>

    <version>2.12.3</version>

</dependency>

<dependency>

    <groupId>jakarta.json</groupId>

    <artifactId>jakarta.json-api</artifactId>

    <version>2.0.1</version>

</dependency>

在Spring Boot项目中，如果引入了以下依赖，便不用单独引入jackson-databind依赖了

<!-- 已经包含了jackson-databind -->

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-web</artifactId>

</dependency>

第二步，配置ObjectMapper

如果不想自定义ObjectMapper的行为，可以省略，这里主要想要支持LocalDate、LocalDateTime类，不然文档中如果包含时间列，反序列成对象时会报错。

在Spring Boot项目中只需加入以下配置即可

package com.wangtao.msgsearch.config;

import com.fasterxml.jackson.annotation.JsonInclude;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;

import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;

import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;

import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;

import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;

import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;

import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;

import org.springframework.boot.autoconfigure.jackson.Jackson2ObjectMapperBuilderCustomizer;

import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import org.springframework.stereotype.Component;

import java.time.LocalDate;

import java.time.LocalDateTime;

import java.time.LocalTime;

import java.time.format.DateTimeFormatter;

@Component

public class JacksonCustomizer implements Jackson2ObjectMapperBuilderCustomizer {

    private static final String STANDARD_PATTERN = "yyyy-MM-dd HH:mm:ss";

    private static final String DATE_PATTERN = "yyyy-MM-dd";

    private static final String TIME_PATTERN = "HH:mm:ss";

    @Override

    public void customize(Jackson2ObjectMapperBuilder builder) {

        // 初始化JavaTimeModule

        JavaTimeModule javaTimeModule = new JavaTimeModule();

        //处理LocalDateTime

        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(STANDARD_PATTERN);

        javaTimeModule.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer(dateTimeFormatter));

        javaTimeModule.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer(dateTimeFormatter));

        //处理LocalDate

        DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern(DATE_PATTERN);

        javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer(dateFormatter));

        javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer(dateFormatter));

        //处理LocalTime

        DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern(TIME_PATTERN);

        javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(timeFormatter));

        javaTimeModule.addDeserializer(LocalTime.class, new LocalTimeDeserializer(timeFormatter));

        /*

         * 1. java.util.Date yyyy-MM-dd HH:mm:ss

         * 2. 支持JDK8 LocalDateTime、LocalDate、 LocalTime

         * 3. Jdk8Module模块支持如Stream、Optional等类

         * 4. 序列化时包含所有字段

         * 5. 在序列化一个空对象时时不抛出异常

         * 6. 忽略反序列化时在json字符串中存在, 但在java对象中不存在的属性

         * 7. 数字序列化成字符穿且调用BigDecimal.toPlainString()方法

         */

        builder.simpleDateFormat(STANDARD_PATTERN)

                .modules(javaTimeModule, new Jdk8Module())

                .serializationInclusion(JsonInclude.Include.ALWAYS)

                .failOnEmptyBeans(false)

                .failOnUnknownProperties(false)

                .featuresToEnable(JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN);

    }

}

第三步，将ElasticsearchClient对象注册到Spring容器中

package com.wangtao.msgsearch.config;

import co.elastic.clients.elasticsearch.ElasticsearchClient;

import co.elastic.clients.json.jackson.JacksonJsonpMapper;

import co.elastic.clients.transport.ElasticsearchTransport;

import co.elastic.clients.transport.rest_client.RestClientTransport;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.apache.http.HttpHost;

import org.elasticsearch.client.RestClient;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

@Configuration

public class ElasticsearchConfig {

    @Bean

    public ElasticsearchClient elasticsearchClient(ObjectMapper objectMapper) {

        RestClient restClient = RestClient.builder(

                new HttpHost("localhost", 9200)).build();

        ElasticsearchTransport transport = new RestClientTransport(

                restClient, new JacksonJsonpMapper(objectMapper));

        return new ElasticsearchClient(transport);

    }

}

API使用

现在就可以来感受下Elasticsearch Java Client API链式以及lambda风格

先准备测试数据

建立索引

PUT /user

{

  "mappings": {

    "properties": {

      "userId": {

        "type": "integer",

        "index": true

      },

      "name": {

        "type": "text",

        "index": true

      },

      "age": {

        "type": "integer",

        "index": true

      },

      "birthday": {

        "type": "date",

        "index": true

      },

      "createTime": {

        "type": "date",

        "index": false,

        "format": "yyyy-MM-dd HH:mm:ss"

      }

    }

  }

}

插入数据

POST /user/_bulk

{"index": {"_id": 1}}

{"userId": 1, "name" : "zhang san", "age" : 20, "birthday" : "2021-08-20", "createTime" : "2022-08-20 12:10:30"}

{"index": {"_id": 2}}

{"userId": 2, "name" : "li si", "age" : 20, "birthday" : "2022-08-20", "createTime" : "2022-08-20 12:10:30"}

{"index": {"_id": 3}}

{"userId": 3, "name" : "zhang san shuo", "age" : 25, "birthday" : "2022-08-20", "createTime" : "2022-08-20 12:10:30"}

{"index": {"_id": 4}}

{"userId": 4, "name" : "wang wu", "age" : 20, "birthday" : "2021-08-20", "createTime" : "2022-08-20 12:10:30"}

根据文档ID查询数据

lambda表达式

 @GetMapping("/{docId}")

public User getByDocId(@PathVariable String docId) throws IOException {

    GetResponse<User> reponse = elasticsearchClient.get(

        g -> g.index("user").id(docId),

        User.class

    );

    if (reponse.found()) {

        return reponse.source();

    } else {

        throw new IllegalArgumentException("not found " + docId);

    }

}

Build模式

@GetMapping("/getByDocIdFluent/{docId}")

public User getByDocIdFluent(@PathVariable String docId) throws IOException {

    GetRequest getRequest = new GetRequest.Builder()

        .index("user")

        .id(docId)

        .build();

    GetResponse<User> reponse = elasticsearchClient.get(getRequest, User.class);

    if (reponse.found()) {

        return reponse.source();

    } else {

        throw new IllegalArgumentException("not found " + docId);

    }

}

搜索操作

实现效果: where name like '%zhang%' and age in (25, 20)

@GetMapping("/search")

public List<User> search() throws IOException {

    Query byName = new MatchQuery.Builder()

        .field("name")

        .query("zhang")

        .build()._toQuery();

    TermsQueryField termsQueryField = new TermsQueryField.Builder()

        .value(Arrays.asList(FieldValue.of(25), FieldValue.of(20)))

        .build();

    Query inAge = new TermsQuery.Builder()

        .field("age")

        .terms(termsQueryField)

        .build()._toQuery();

    Query query = new BoolQuery.Builder()

        .must(byName, inAge)

        .build()._toQuery();

    SearchRequest searchRequest = new SearchRequest.Builder()

        .index("user")

        .query(query)

        .build();

    SearchResponse<User> response = elasticsearchClient.search(

        searchRequest, User.class);

    List<Hit<User>> hits = response.hits().hits();

    return hits.stream().map(Hit::source).collect(Collectors.toList());

}