ElasticSearch的JavaAPI简单使用

Posted 2021-05-08 唐宋xy

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ES是一个**开源的高扩展的分布式全文搜索引擎，**是整个Elastic Stack技术栈的核心。它可以近乎实时的存储、检索数据；本身扩展性很好，可以扩展到上百台服务器，处理PB级别的数据。Elasticsearch软件是由Java语言开发的，所以也可以通过Java API的方式对Elasticsearch服务进行访问，并且操作的方式基本和Http操作一致

本文已经收录到我的Github: https://github.com/chenliang15405/common-study/tree/main/elasticsearch-demo

Maven依赖

pom.xml中加入ES需要的依赖

<dependencies>
    <dependency>
        <groupId>org.elasticsearch</groupId>
        <artifactId>elasticsearch</artifactId>
        <version>7.8.0</version>
    </dependency>
    <!-- elasticsearch的客户端 -->
    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-high-level-client</artifactId>
        <version>7.8.0</version>
    </dependency>
    <!-- elasticsearch依赖2.x的log4j -->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.8.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.8.2</version>
</dependency>
	<dependency>
		<groupId>com.fasterxml.jackson.core</groupId>
		<artifactId>jackson-databind</artifactId>
		<version>2.9.9</version>
	</dependency>
    <!-- junit单元测试 -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
</dependencies>

如果在运行时报错
```
java.lang.NoSuchMethodError: org.elasticsearch.client.Request.addParameters
```
那么应该是发生了依赖冲突，新建一个Maven项目，最好不要直接创建springboot项目，可能会有依赖冲突，将上面的依赖加入到maven项目的pom中

链接ES客户端

因为使用的highLevel的ES客户端，所以可以很方便的连接到ES，只需要通过host和port就可以直接连接

public static void main(String[] args) throws IOException {
    RestHighLevelClient esClient = new RestHighLevelClient(
        RestClient.builder(new HttpHost("localhost", 9200, "http"))
    );

    esClient.close();
}

如果代码执行正常，没有报错那么就表示正常连接到了ES节点，可以通过获取到的RestHighLevelClient对象进行操作

索引操作

加入了maven依赖，那么就可以通过Java客户端链接到ES进行操作，首先进行索引的基本操作

创建索引

RestHighLevelClient esClient = new RestHighLevelClient(
    RestClient.builder(new HttpHost("localhost", 9200, "http"))
);
@Test
public void index_create() throws IOException {
    // 创建索引 - 请求对象
    CreateIndexRequest request = new CreateIndexRequest("test");
    // 发送请求，获取响应
    CreateIndexResponse response = esClient.indices().create(request, RequestOptions.DEFAULT);
    boolean acknowledged = response.isAcknowledged();
    // 响应状态
    System.out.println("操作状态 = " + acknowledged);
}

查询索引

RestHighLevelClient esClient = new RestHighLevelClient(
    RestClient.builder(new HttpHost("localhost", 9200, "http"))
);

@Test
public void index_get() throws IOException {

    GetIndexRequest request = new GetIndexRequest("test");

    GetIndexResponse response = esClient.indices().get(request, RequestOptions.DEFAULT);

    System.out.println(Arrays.toString(response.getIndices()));
    System.out.println(response.getMappings());
    System.out.println(response.getSettings());
}

删除索引

RestHighLevelClient esClient = new RestHighLevelClient(
    RestClient.builder(new HttpHost("localhost", 9200, "http"))
);

@Test
public void index_delete() throws IOException {

    DeleteIndexRequest request = new DeleteIndexRequest("test");

    AcknowledgedResponse response = esClient.indices().delete(request, RequestOptions.DEFAULT);

    System.out.println(response.isAcknowledged());
}

文档操作

文档作为数据的对象，可以通过ES的客户端对象直接操作

RestHighLevelClient对象和上面的创建方式相同，此处省略

文档基本操作

创建文档

@Test
public void doc_create() throws IOException {
    IndexRequest request = new IndexRequest();
    // 设置操作的索引和当前插入的文档的id
    request.index("people").id("1001");

    User user = new User();
    user.setName("张三");
    user.setAge(10);
    user.setSex("男");

    ObjectMapper mapper = new ObjectMapper();
    String userJson = mapper.writeValueAsString(user);

    request.source(userJson, XContentType.JSON);

    IndexResponse response = esClient.index(request, RequestOptions.DEFAULT);

    System.out.println(response);

    System.out.println("_index" + response.getIndex());
    System.out.println("_id" + response.getId());
    System.out.println("_result" + response.getResult());
}

更新文档

@Test
public void doc_update() throws IOException {
    UpdateRequest request = new UpdateRequest();
    request.index("people").id("1001");

    request.doc(XContentType.JSON, "sex", "女");

    UpdateResponse response = esClient.update(request, RequestOptions.DEFAULT);

    System.out.println(response);
}

查询文档

@Test
public void doc_get() throws IOException {

    GetRequest request = new GetRequest();
    request.index("people").id("1001");

    GetResponse response = esClient.get(request, RequestOptions.DEFAULT);

    System.out.println(response);
    System.out.println(response.getSource());
}

删除文档

@Test
public void doc_delete() throws IOException {
    DeleteRequest request = new DeleteRequest();
    request.index("people").id("1001");

    DeleteResponse response = esClient.delete(request, RequestOptions.DEFAULT);
    System.out.println(response);
}

文档批量操作

一般操作ES的数据都是批量保存或者批量删除，如果通过一条一条的操作，那么效率非常的低，可以通过批量操作API提高效率

批量保存

@Test
public void doc_insert_batch() throws IOException {
    BulkRequest request = new BulkRequest();
    request.add(new IndexRequest().index("people").id("1001").source(XContentType.JSON, "name", "张三", "sex", "男", "age", 10));
    request.add(new IndexRequest().index("people").id("1002").source(XContentType.JSON, "name", "李四", "sex", "男", "age", 11));
    request.add(new IndexRequest().index("people").id("1003").source(XContentType.JSON, "name", "王五", "sex", "男", "age", 12));
    request.add(new IndexRequest().index("people").id("1004").source(XContentType.JSON, "name", "王五1", "sex", "男", "age", 8));
    request.add(new IndexRequest().index("people").id("1005").source(XContentType.JSON, "name", "王五2", "sex", "男", "age", 9));
    request.add(new IndexRequest().index("people").id("1006").source(XContentType.JSON, "name", "王五33", "sex", "男", "age", 7));

    BulkResponse response = esClient.bulk(request, RequestOptions.DEFAULT);

    System.out.println(response.getTook());
    System.out.println(Arrays.toString(response.getItems()));
}

批量删除

@Test
public void doc_delete_batch() throws IOException {
    BulkRequest request = new BulkRequest();
    request.add(new DeleteRequest().index("people").id("1001"));
    request.add(new DeleteRequest().index("people").id("1002"));
    request.add(new DeleteRequest().index("people").id("1003"));

    BulkResponse response = esClient.bulk(request, RequestOptions.DEFAULT);

    System.out.println(response.getTook());
    System.out.println(response);
}

文档高级查询

高级查询、分组查询、分页、排序、聚合操作等，作为ES常用的查询操作，ES的Java客户端也提供了好用的API进行操作

查询指定索引的所有数据

@Test
public void match_all() throws IOException {
    SearchRequest request = new SearchRequest();
    request.indices("people");

    SearchSourceBuilder builder = new SearchSourceBuilder();
    builder.query(QueryBuilders.matchAllQuery());

    request.source(builder);

    SearchResponse response = esClient.search(request, RequestOptions.DEFAULT);

    SearchHits hits = response.getHits();
    System.out.println("took:" + response.getTook());
    System.out.println("timeout:" + response.isTimedOut());
    System.out.println("total:" + hits.getTotalHits());
    System.out.println("MaxScore:" + hits.getMaxScore());
    System.out.println("hits========>>");
    for (SearchHit hit : hits) {
        //输出每条查询的结果信息
        System.out.println(hit.getSourceAsString());
    }
    System.out.println("<<========");
}

term查询

@Test
public void query_term() throws IOException {
    SearchRequest request = new SearchRequest();
    request.indices("people");

    SearchSourceBuilder builder = new SearchSourceBuilder();
    builder.query(QueryBuilders.termQuery("age", 10));

    request.source(builder);

    SearchResponse response = esClient.search(request, RequestOptions.DEFAULT);

    SearchHits hits = response.getHits();
    System.out.println("took:" + response.getTook());
    System.out.println("timeout:" + response.isTimedOut());
    System.out.println("total:" + hits.getTotalHits());
    System.out.println("MaxScore:" + hits.getMaxScore());
    System.out.println("hits========>>");
    for (SearchHit hit : hits) {
        //输出每条查询的结果信息
        System.out.println(hit.getSourceAsString());
    }
    System.out.println("<<========");
}

分页查询

@Test
public void query_page() throws IOException {
    SearchRequest request = new SearchRequest();
    request.indices("people");

    SearchSourceBuilder builder = new SearchSourceBuilder();
    builder.query(QueryBuilders.matchAllQuery());

    // from指定的是页数开始的偏移量， （当前页数 - 1）* size
    builder.from(0);
    builder.size(3);

    request.source(builder);

    SearchResponse response = esClient.search以上是关于ElasticSearch的JavaAPI简单使用的主要内容，如果未能解决你的问题，请参考以下文章 
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