一、ElasticSearch 介绍

Elasticsearch 是一个分布式、高扩展、高实时的搜索与数据分析引擎。它能很方便的使大量数据具有搜索、分析和探索的能力。充分利用Elasticsearch的水平伸缩性，能使数据在生产环境变得更有价值。Elasticsearch 的实现原理主要分为以下几个步骤，首先用户将数据提交到Elasticsearch 数据库中，再通过分词控制器去将对应的语句分词，将其权重和分词结果一并存入数据，当用户搜索数据时候，再根据权重将结果排名，打分，再将返回结果呈现给用户。

ElasticSearch 官网地址：https://www.elastic.co/cn/

二、环境准备

在开始开发之前，我们需要准备一些环境配置:

jdk 1.8 或其他更高版本
开发工具 IDEA
管理依赖 Maven
ElasticSearch环境，此处使用docker搭建，ElasticSearch 版本为7.17.7
Spring Boot 2.X

三、创建Spring Boot项目导入依赖

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

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

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

注意：依赖版本必须与你当前所用的版本保持一致，否则连接失败

四、创建高级客户端

新建config目录存放项目配置类

@Configuration
public class ElasticSearchClientConfig {
    @Bean
    public RestHighLevelClient restHighLevelClient(){
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(
                        new HttpHost("服务器IP地址", 9200, "http")));
        return client;
    }
}

五、基本操作

索引操作

@SpringBootTest
class DemoApplicationTests {

    @Autowired
    private RestHighLevelClient restHighLevelClient;

    /**
    * 创建索引
    **/
    @Test
    void testCreateIndex() throws IOException {
        //1.创建索引请求
        CreateIndexRequest request = new CreateIndexRequest("lt");
        //2.客户端执行请求IndicesClient，执行create方法创建索引，请求后获得响应
        CreateIndexResponse response=
                restHighLevelClient.indices().create(request, RequestOptions.DEFAULT);
        System.out.println(response);
    }

    /**
     * 判断索引是否存在
     **/
    @Test
    void testExistIndex() throws IOException {
        //1.查询索引请求
        GetIndexRequest request=new GetIndexRequest("lt");
        //2.执行exists方法判断是否存在
        boolean exists=restHighLevelClient.indices().exists(request,RequestOptions.DEFAULT);
        System.out.println(exists ? "存在" : "消失");
    }

    /**
     * 删除索引
     **/
    @Test
    void testDeleteIndex() throws IOException {
        //1.删除索引请求
        DeleteIndexRequest request=new DeleteIndexRequest("lt");
        //执行delete方法删除指定索引
        AcknowledgedResponse delete = restHighLevelClient.indices().delete(request, RequestOptions.DEFAULT);
        System.out.println(delete.isAcknowledged() ? "删除成功" : "删除失败");
    }
}

文档操作

创建实体类User

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class User {
    private String name;
    private Integer age;
    private String[] funny;
}

文档相关操作代码

/**
 * 创建文档
 **/
@Test
void testAddUser() throws IOException {
    //1.创建对象
    User user=new User("小赵",21,new String[]{"篮球","吃饭"});
    //2.创建请求
    IndexRequest request=new IndexRequest("lt");
    //3.设置规则 PUT /lt/_doc/1
    //设置文档id=6，设置超时=1s等，不设置会使用默认的
    //同时支持链式编程如 request.id("6").timeout("1s");
    request.id("6");
    request.timeout("1s");

    //4.将数据放入请求，要将对象转化为json格式
    //XContentType.JSON，告诉它传的数据是JSON类型
    request.source(JSONValue.toJSONString(user), XContentType.JSON);

    //5.客户端发送请求，获取响应结果
    IndexResponse indexResponse=restHighLevelClient.index(request,RequestOptions.DEFAULT);
    System.out.println(indexResponse.toString());
    System.out.println(indexResponse.status());
}

/**
 * 获取文档数据
 **/
@Test
void testGetUser() throws IOException {
    //1.创建请求,指定索引、文档id
    GetRequest request=new GetRequest("lt","1");
    GetResponse getResponse=restHighLevelClient.get(request,RequestOptions.DEFAULT);

    System.out.println(getResponse);//获取响应结果
    //getResponse.getSource() 返回的是Map集合
    System.out.println(getResponse.getSourceAsString());//获取响应结果source中内容，转化为字符串
}

/**
 * 更新文档
 **/
@Test
void testUpdateUser() throws IOException {
    //1.创建请求,指定索引、文档id
    UpdateRequest request=new UpdateRequest("lt","6");

    User user =new User("xiaozhao",21,new String[]{"xxx","xxx"});
    //将创建的对象放入文档中
    request.doc(JSONValue.toJSONString(user),XContentType.JSON);

    UpdateResponse updateResponse=restHighLevelClient.update(request,RequestOptions.DEFAULT);
    System.out.println(updateResponse.status());
}

/**
 * 删除文档
 **/
@Test
void testDeleteUser() throws IOException {
    //创建删除请求，指定要删除的索引与文档ID
    DeleteRequest request=new DeleteRequest("lt","6");

    DeleteResponse updateResponse=restHighLevelClient.delete(request,RequestOptions.DEFAULT);
    System.out.println(updateResponse.status());
}

批量插入数据

/**
 * 批量插入数据
 **/
@Test
void testBulkAddUser() throws IOException {
    BulkRequest bulkRequest=new BulkRequest();
    //设置超时
    bulkRequest.timeout("10s");

    ArrayList<User> list=new ArrayList<>();
    list.add(new User("Java",25,new String[]{"内卷"}));
    list.add(new User("Go",18,new String[]{"内卷"}));
    list.add(new User("C",30,new String[]{"内卷"}));
    list.add(new User("C++",26,new String[]{"内卷"}));
    list.add(new User("Python",20,new String[]{"内卷"}));

    int id=1;
    //批量处理请求
    for (User u :list){
        //不设置id会生成随机id
        bulkRequest.add(new IndexRequest("ljx666")
                .id(""+(id++))
                .source(JSONValue.toJSONString(u),XContentType.JSON));
    }

    BulkResponse bulkResponse=restHighLevelClient.bulk(bulkRequest,RequestOptions.DEFAULT);
    System.out.println(bulkResponse.hasFailures());//是否执行失败,false为执行成功
}

其他操作

@Test
void testSearch() throws IOException {
    SearchRequest searchRequest=new SearchRequest("ljx666");//里面可以放多个索引
    SearchSourceBuilder sourceBuilder=new SearchSourceBuilder();//构造搜索条件

    //此处可以使用QueryBuilders工具类中的方法
    //1.查询所有
    sourceBuilder.query(QueryBuilders.matchAllQuery());
    //2.查询name中含有Java的
    sourceBuilder.query(QueryBuilders.multiMatchQuery("java","name"));
    //3.分页查询
    sourceBuilder.from(0).size(5);

    //4.按照score正序排列
    //sourceBuilder.sort(SortBuilders.scoreSort().order(SortOrder.ASC));
    //5.按照id倒序排列（score会失效返回NaN）
    //sourceBuilder.sort(SortBuilders.fieldSort("_id").order(SortOrder.DESC));

    //6.给指定字段加上指定高亮样式
    HighlightBuilder highlightBuilder=new HighlightBuilder();
    highlightBuilder.field("name").preTags("<span style='color:red;'>").postTags("</span>");
    sourceBuilder.highlighter(highlightBuilder);

    searchRequest.source(sourceBuilder);
    SearchResponse searchResponse=restHighLevelClient.search(searchRequest,RequestOptions.DEFAULT);

    //获取总条数
    System.out.println(searchResponse.getHits().getTotalHits().value);
    //输出结果数据（如果不设置返回条数，大于10条默认只返回10条）
    SearchHit[] hits=searchResponse.getHits().getHits();
    for(SearchHit hit :hits){
        System.out.println("分数:"+hit.getScore());
        Map<String,Object> source=hit.getSourceAsMap();
        System.out.println("index->"+hit.getIndex());
        System.out.println("id->"+hit.getId());
        for(Map.Entry<String,Object> s:source.entrySet()){
            System.out.println(s.getKey()+"--"+s.getValue());
        }
    }
}