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这里分类和汇总了欣宸的全部原创(含配套源码)：https://github.com/zq2599/blog_demos

本篇概览

• 本篇是《java与es8实战》系列的第四篇，系列文章写到现在，连个HelloWorld都没运行起来，实在说不过去了…
• 因此，本篇总体目标明确：实战在SpringBoot应用中操作elasticsearch8
• 为了降低难度，本篇部署的elasticsearch8未设置安全检查，无需证书、账号、密码，只要连接到es的IP和端口就能执行操作
• 总体目标可以拆解为两个子任务

1. 在SpringBoot中连接elasticsearch8
2. 在SpringBoot中使用elasticsearch8官方的Java API Client

• 接下来直接开始

部署elasticsearch集群(无安全检查)

• 关于快速部署elasticsearch集群(无安全检查)，可以参考《docker-compose快速部署elasticsearch-8.x集群+kibana》

Java应用连接elasticsearch的核心套路

• 不论是直连，还是带安全检查的连接，亦或是与SpringBoot的集成使之更方便易用，都紧紧围绕着一个不变的核心套路，该套路由两部分组成，掌握了它们就能在各种条件下成功连接es

1. 首先，是builder pattern，连接es有关的代码，各种对象都是其builder对象的build方法创建的，建议您提前阅读《java与es8实战之一》一文，看完后，满屏的builder代码可以从丑变成美…
2. 其次，就是java应用能向es发请求的关键：ElasticsearchClient对象，该对象的创建是有套路的，如下图，先创建RestClient，再基于RestClient创建ElasticsearchTransport，最后基于ElasticsearchTransport创建ElasticsearchClient，这是个固定的套路，咱们后面的操作都是基于此的，可能会加一点东西，但不会改变流程和图中的对象

• 准备完毕，开始写代码

新建子工程

• 为了便于管理依赖库版本和源码，《java与es8实战》系列的所有代码都以子工程的形式存放在父工程elasticsearch-tutorials中
• 《java与es8实战之二：实战前的准备工作》一文说明了创建父工程的详细过程
• 在父工程elasticsearch-tutorials中新建名为basic-crud的子工程，其pom.xml内容如下

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <!-- 请改为自己项目的parent坐标 -->
    <parent>
        <artifactId>elasticsearch-tutorials</artifactId>
        <groupId>com.bolingcavalry</groupId>
        <version>1.0-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <!-- 请改为自己项目的artifactId -->
    <artifactId>basic-crud</artifactId>
    <packaging>jar</packaging>
    <!-- 请改为自己项目的name -->
    <name>basic-crud</name>
    <url>https://github.com/zq2599</url>

    <!--不用spring-boot-starter-parent作为parent时的配置-->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>

                <version>${springboot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

        <!-- 不加这个，configuration类中，IDEA总会添加一些提示 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>

            <!-- exclude junit 4 -->
            <exclusions>
                <exclusion>
                    <groupId>junit</groupId>
                    <artifactId>junit</artifactId>
                </exclusion>
            </exclusions>

        </dependency>

        <!-- junit 5 -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- elasticsearch引入依赖  start -->
        <dependency>
            <groupId>co.elastic.clients</groupId>
            <artifactId>elasticsearch-java</artifactId>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>

        <!-- 使用spring boot Maven插件时需要添加该依赖 -->
        <dependency>
            <groupId>jakarta.json</groupId>
            <artifactId>jakarta.json-api</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- 需要此插件，在执行mvn test命令时才会执行单元测试 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>3.0.0-M4</version>
                <configuration>
                    <skipTests>false</skipTests>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>

        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.*</include>
                </includes>
            </resource>
        </resources>
    </build>
</project>

编码：配置文件

• 先准备好配置文件application.yml，内容如下，很简单，只有es的地址信息

elasticsearch:
  # 多个IP逗号隔开
  hosts: 127.0.0.1:9200

编码：配置类

• 首先把启动类写好，平平无奇的启动类BasicCrudApplication.java

@SpringBootApplication
public class BasicCrudApplication {
    public static void main(String[] args) {
        SpringApplication.run(BasicCrudApplication.class, args);
    }
}

• 然后是配置类ClientConfig.java，这是本篇的关键，操作ES所需的ElasticsearchClient实例如何创建，ES的IP地址如何传入，全部写在这里了

package com.bolingcavalry.basic.config;

import co.elastic.clients.elasticsearch.ElasticsearchAsyncClient;
import co.elastic.clients.elasticsearch.ElasticsearchClient;
import co.elastic.clients.json.jackson.JacksonJsonpMapper;
import co.elastic.clients.transport.rest_client.RestClientTransport;
import lombok.Setter;
import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.StringUtils;

@ConfigurationProperties(prefix = "elasticsearch") //配置的前缀
@Configuration
public class ClientConfig {

    @Setter
    private String hosts;

    /**
     * 解析配置的字符串，转为HttpHost对象数组
     * @return
     */
    private HttpHost[] toHttpHost() {
        if (!StringUtils.hasLength(hosts)) {
            throw new RuntimeException("invalid elasticsearch configuration");
        }

        String[] hostArray = hosts.split(",");
        HttpHost[] httpHosts = new HttpHost[hostArray.length];
        HttpHost httpHost;
        for (int i = 0; i < hostArray.length; i++) {
            String[] strings = hostArray[i].split(":");
            httpHost = new HttpHost(strings[0], Integer.parseInt(strings[1]), "http");
            httpHosts[i] = httpHost;
        }

        return httpHosts;
    }

    @Bean
    public ElasticsearchClient elasticsearchClient() {
        HttpHost[] httpHosts = toHttpHost();
        RestClient restClient = RestClient.builder(httpHosts).build();
        RestClientTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());
        return new ElasticsearchClient(transport);
    }

    @Bean
    public ElasticsearchAsyncClient elasticsearchAsyncClient() {
        HttpHost[] httpHosts = toHttpHost();
        RestClient restClient = RestClient.builder(httpHosts).build();
        RestClientTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());
        return new ElasticsearchAsyncClient(transport);
    }
}

• 从上面的代码可以看出，配置类已经向Spring容器注册了ElasticsearchClient实例，后面的业务都可以使用此实例来操作ES

编码：服务类

• 本篇只是为了演示SpringBoot应用如何连接和操作ES，还不会深入ES操作的细节，因此只对索引做一些基本操作即可
• 先写一个接口IndexService.java，里面定义了多个索引操作的方法

package com.bolingcavalry.basic.service;

import co.elastic.clients.elasticsearch._types.mapping.TypeMapping;
import co.elastic.clients.elasticsearch.indices.IndexSettings;
import co.elastic.clients.util.ObjectBuilder;

import java.io.IOException;
import java.util.function.Function;

public interface IndexService {

    /**
     * 新建指定名称的索引
     * @param name
     * @throws IOException
     */
    void addIndex(String name) throws IOException;

    /**
     * 检查指定名称的索引是否存在
     * @param name
     * @return
     * @throws IOException
     */
    boolean indexExists(String name) throws IOException;

    /**
     * 删除指定索引
     * @param name
     * @throws IOException
     */
    void delIndex(String name) throws IOException;

    /**
     * 创建索引，指定setting和mapping
     * @param name 索引名称
     * @param settingFn 索引参数
     * @param mappingFn 索引结构
     * @throws IOException
     */
    void create(String name,
                Function<IndexSettings.Builder, ObjectBuilder<IndexSettings>> settingFn,
                Function<TypeMapping.Builder, ObjectBuilder<TypeMapping>> mappingFn) throws IOException;
}

• 然后接口的实现，可见所有操作都是在调用ElasticsearchClient实例的API

package com.bolingcavalry.basic.service.impl;

import co.elastic.clients.elasticsearch.ElasticsearchClient;
import co.elastic.clients.elasticsearch._types.mapping.TypeMapping;
import co.elastic.clients.elasticsearch.indices.IndexSettings;
import co.elastic.clients.util.ObjectBuilder;
import com.bolingcavalry.basic.service.IndexService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Service;

import java.io.IOException;
import java.util.function.Function;

@Service
public class IndexServiceImpl implements IndexService {

    @Autowired
    private ElasticsearchClient elasticsearchClient;

    @Override
    public void addIndex(String name) throws IOException {
        ApplicationContext applicationContext;
        elasticsearchClient.indices().create(c -> c.index(name));
    }

    @Override
    public boolean indexExists(String name) throws IOException {
        ApplicationContext a;
        return elasticsearchClient.indices().exists(b -> b.index(name)).value();
    }

    @Override
    public void delIndex(String name) throws IOException {
        elasticsearchClient.indices().delete(c -> c.index(name));
    }

    @Override
    public void create(String name,
                       Function<IndexSettings.Builder, ObjectBuilder<IndexSettings>> settingFn,
                       Function<TypeMapping.Builder, ObjectBuilder<TypeMapping>> mappingFn) throws IOException {
       elasticsearchClient
               .indices()
               .create(c -> c
                       .index(name)
                       .settings(settingFn)
                       .mappings(mappingFn)
               );
    }
}

• 以上就是本篇的功能代码了，连接ES在其上进行索引相关操作

编码：单元测试

• 为了验证上述代码是否生效，接下来写一个单元测试类IndexServiceTest.java，可以重点关注createIndex方法，里面演示了Builder pattern构建参数的详细步骤

package com.bolingcavalry.basic.service;

import co.elastic.clients.elasticsearch._types.mapping.Property;
import co.elastic.clients.elasticsearch._types.mapping.TypeMapping;
import co.elastic.clients.elasticsearch.indices.IndexSettings;
import co.elastic.clients.util.ObjectBuilder;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.function.Function;

@SpringBootTest
class IndexServiceTest {

    @Autowired
    IndexService indexService;

    @Test
    void addIndex() throws Exception {
        String indexName = "test_index";

        Assertions.assertFalse(indexService.indexExists(indexName));
        indexService.addIndex(indexName);
        Assertions.assertTrue(indexService.indexExists(indexName));
        indexService.delIndex(indexName);
        Assertions.assertFalse(indexService.indexExists(indexName));
    }

    @Test
    void indexExists() throws Exception {
        indexService.indexExists("a");
    }

    @Test
    void createIndex() throws Exception {
        // 索引名
        String indexName = "product002";

        // 构建setting时，builder用到的lambda
        Function<IndexSettings.Builder, ObjectBuilder<IndexSettings>> settingFn = sBuilder -> sBuilder
                .index(iBuilder -> iBuilder
                        // 三个分片
                        .numberOfShards("3")
                        // 一个副本
                        .numberOfReplicas("1")
                );

        // 新的索引有三个字段，每个字段都有自己的property，这里依次创建
        Property keywordProperty = Property.of(pBuilder -> pBuilder.keyword(kBuilder -> kBuilder.ignoreAbove(256)));
        Property textProperty = Property.of(pBuilder -> pBuilder.text(tBuilder -> tBuilder));
        Property integerProperty = Property.of(pBuilder -> pBuilder.integer(iBuilder -> iBuilder));

        // // 构建mapping时，builder用到的lambda
        Function<TypeMapping.Builder, ObjectBuilder<TypeMapping>> mappingFn = mBuilder -> mBuilder
                .properties("name", keywordProperty)
                .properties("description", textProperty)
                .properties("price", integerProperty);

        // 创建索引，并且指定了setting和mapping
        indexService.create(indexName, settingFn, mappingFn);
    }
}

• 确保不做安全检查的ES集群运行正常，再执行单元测试，如下图，顺利通过，证明所有对ES的操作都符合预期

• 再用eshead观察product002索引的情况，如下图，三个分片，一个副本，与代码中设置的一致

• 至此最简单的连接和操作ES实战已经完成，希望本篇能给您一些参考，助您顺利完成基本操作

是不是线程安全的

• 官方回应：https://discuss.elastic.co/t/is-elasticsearch-client-is-thread-safe/151745
• 有人在问这个问题，es团队的成员Simon Willnauer的回答是：java的client肯定是线程安全的，golang的不清楚

• 对我来说，有他这话就够了，至于golang的嘛，在本文就不讨论了

源码下载

• 本篇实战的完整源码可在GitHub下载到，地址和链接信息如下表所示(https://github.com/zq2599/blog_demos)

• 这个git项目中有多个文件夹，本次实战的源码在elasticsearch-tutorials文件夹下，如下图红框

• elasticsearch-tutorials是个父工程，里面有多个module，本篇实战的module是basic-crud，如下图红框

你不孤单，欣宸原创一路相伴

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