1. 關(guān)于 Elasticsearch

Elasticsearch 是一個(gè)分布式的 RESTful 搜索和分析引擎遍膜，可用來集中存儲(chǔ)您的數(shù)據(jù)郎仆，以便您對(duì)形形色色、規(guī)模不一的數(shù)據(jù)進(jìn)行搜索捺癞、索引和分析憾赁。
我們可以在這里下載Elasticsearch的安裝文件，建議下載二進(jìn)制壓縮文件赠橙。對(duì)于本文的讀者耽装，您只需解壓下載的文件，然后執(zhí)行下面的命令即可啟動(dòng)Elasticsearch期揪。

cd ./elasticsearch-7.8.0/bin
./elasticsearch

2. Spring Data

?Spring Data 是 Spring 的一個(gè)子項(xiàng)目掉奄。用于簡化數(shù)據(jù)訪問，支持NoSQL 和關(guān)系數(shù)據(jù)庫凤薛，map-reduce框架和基于云的數(shù)據(jù)服務(wù)姓建。其主要目標(biāo)是使數(shù)據(jù)的訪問變得方便快捷。從官網(wǎng)中可以看到目前Spring Data支持的數(shù)據(jù)種類非常多缤苫。Elasticsearch是其中的一種速兔。

2.1 Maven依賴

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-elasticsearch</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

2.2 配置文件

編輯application.properties文件，增加如下內(nèi)容：

spring.data.elasticsearch.client.reactive.endpoints=127.0.0.1:9200
spring.data.elasticsearch.repositories.enabled=true

2.3 定義實(shí)體類

//注意indexName要小寫
@Document(indexName = "blog")
@Setter
@Getter
@ToString
public class Article {
    @Id
    private String id;
    private String title;
    @Field(type = FieldType.Nested, includeInParent = true)
    private List<Author> authors;

    public Article(String title) {
        this.title = title;
    }
}

public class Author {
    private String name;
    public Author(String name) {
        this.name = name;
    }
}

2.4 定義Repository接口

@Repository
public interface ArticleRepository extends ElasticsearchRepository<Article,String> {

    //下面的這兩個(gè)查詢的作用是一樣的活玲。一個(gè)采用默認(rèn)的實(shí)現(xiàn)方式涣狗，一個(gè)采用自定義的實(shí)現(xiàn)方式
    Page<Article> findByAuthorsName(String name, Pageable pageable);
    @Query("{\"bool\": {\"must\": [{\"match\": {\"authors.name\": \"?0\"}}]}}")
    Page<Article> findByAuthorsNameUsingCustomQuery(String name, Pageable pageable);

    //搜索title字段
    Page<Article> findByTitleIsContaining(String word,Pageable pageable);
    
    Page<Article> findByTitle(String title,Pageable pageable);
}

3 使用

3.1 在測試類中自動(dòng)裝載repository和template實(shí)例

    @Autowired
    private ArticleRepository articleRepository;
    @Autowired
    private ElasticsearchRestTemplate elasticsearchRestTemplate;

3.2 檢查index是否存在

    //檢查相應(yīng)的索引是否存在谍婉，如果spring.data.elasticsearch.repositories.enabled=True,則會(huì)自動(dòng)創(chuàng)建索引
    private boolean checkIndexExists(Class<?> cls){
        boolean isExist = elasticsearchRestTemplate.indexOps(cls).exists();
        //獲取索引名
        String indexName = cls.getAnnotation(Document.class).indexName();
        System.out.printf("index %s is %s\n", indexName, isExist ? "exist" : "not exist");
        return isExist;
    }
    @Test
    void checkIndex() {
        checkIndexExists(Article.class);
    }

3.2 新增數(shù)據(jù)

    @Test
     void save(){
        Article article = new Article("Spring Data Elasticsearch");
        article.setAuthors(asList(new Author("LaoAlex"),new Author("John")));
        articleRepository.save(article);

        article = new Article("Spring Data Elasticsearch2");
        article.setAuthors(asList(new Author("LaoAlex"),new Author("King")));
        articleRepository.save(article);

        article = new Article("Spring Data Elasticsearch3");
        article.setAuthors(asList(new Author("LaoAlex"),new Author("Bill")));
        articleRepository.save(article);
    }

3.3 查詢

    @Test
    void queryAuthorName() throws JsonProcessingException {
        Page<Article> articles = articleRepository.findByAuthorsName("LaoAlex", PageRequest.of(0,10));
        //將對(duì)象轉(zhuǎn)為Json字符串
        ObjectWriter objectWriter = new ObjectMapper().writer().withDefaultPrettyPrinter();
        String json = objectWriter.writeValueAsString(articles);
        System.out.println(json);
    }

    //使用自定義查詢
    @Test
    void queryAuthorNameByCustom() throws JsonProcessingException {
        Page<Article> articles = articleRepository.findByAuthorsNameUsingCustomQuery("John",PageRequest.of(0,10));
        //將對(duì)象轉(zhuǎn)為Json字符串
        ObjectWriter objectWriter = new ObjectMapper().writer().withDefaultPrettyPrinter();
        String json = objectWriter.writeValueAsString(articles);
        System.out.println(json);
    }

3.4 使用template進(jìn)行查詢

    //使用Template進(jìn)行關(guān)鍵字查詢
    //關(guān)于正則表達(dá)式可以參考https://www.runoob.com/java/java-regular-expressions.html
    //.*data.* 可以匹配ddata, dataa等
    @Test
    void queryTileContainByTemplate() throws JsonProcessingException {
        Query query = new NativeSearchQueryBuilder().withFilter(regexpQuery("title",".*elasticsearch2.*")).build();
        SearchHits<Article> articles = elasticsearchRestTemplate.search(query, Article.class, IndexCoordinates.of("blog"));
        //將對(duì)象轉(zhuǎn)為Json字符串
        ObjectWriter objectWriter = new ObjectMapper().writer().withDefaultPrettyPrinter();
        String json = objectWriter.writeValueAsString(articles);
        System.out.println(json);
    }

3.5 更新

    @Test
    void update() throws JsonProcessingException {
        Page<Article> articles = articleRepository.findByTitle("Spring Data Elasticsearch",PageRequest.of(0,10));
        //將對(duì)象轉(zhuǎn)為Json字符串
        ObjectWriter objectWriter = new ObjectMapper().writer().withDefaultPrettyPrinter();
        String json = objectWriter.writeValueAsString(articles);
        System.out.println(json);

        Article article = articles.getContent().get(0);
        System.out.println(article);
        article.setAuthors(null);
        articleRepository.save(article);
    }

3.6 刪除

    @Test
    void delete(){
        Page<Article> articles = articleRepository.findByTitle("Spring Data Elasticsearch",PageRequest.of(0,10));
        Article article = articles.getContent().get(0);
        articleRepository.delete(article);
    }

4 總結(jié)

本文使用Spring Data對(duì)Elasticsearch進(jìn)行了增、刪镀钓、改穗熬、查操作。原代碼以及放在GitHub上(https://github.com/superhq/LaoAlexJava.git)丁溅。

Spring Data Elasticsearch 使用介紹