Java API操作ES

wenxuehai發表於2024-04-02
JavaAPI

1、專案搭建

Elasticsearch 軟體是由 Java 語言開發的，所以也可以透過 Java API 的方式對 Elasticsearch服務進行訪問。

先 IDEA 開發工具中建立簡單的 java se Maven 專案(模組也可)，如下：

修改 pom 檔案，增加 Maven 依賴關係如下：

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>org.elasticsearch</groupId>
      <artifactId>elasticsearch</artifactId>
      <version>7.8.0</version>
    </dependency>
    <!-- elasticsearch 的客戶端 -->
    <dependency>
      <groupId>org.elasticsearch.client</groupId>
      <artifactId>elasticsearch-rest-high-level-client</artifactId>
      <version>7.8.0</version>
    </dependency>

    <!-- elasticsearch 依賴 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>
  </dependencies>

2、Elasticsearch 客戶端物件

程式碼如下：

import java.io.IOException;

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

public class HelloElasticsearch {

    public static void main(String[] args) throws IOException {
        // 建立客戶端物件
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("127.0.0.1", 9200, "http")));
//        ...
        System.out.println("ES客戶端物件：" + client);

        // 關閉客戶端連線
        client.close();
    }
}

響應如下：

3、索引操作

3.1、建立索引

package org.example;

import org.apache.http.HttpHost;
import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
import org.elasticsearch.action.admin.indices.create.CreateIndexResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

import java.io.IOException;

public class CreateIndex {

    public static void main(String[] args) throws IOException {
        // 建立客戶端物件
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));

        // 建立索引 - 請求物件
        CreateIndexRequest request = new CreateIndexRequest("user2");
        // 傳送請求，獲取響應
        CreateIndexResponse response = client.indices().create(request,
                RequestOptions.DEFAULT);
        boolean acknowledged = response.isAcknowledged();
        // 響應狀態
        System.out.println("操作狀態 = " + acknowledged);

        // 關閉客戶端連線
        client.close();
    }

}

響應如下：

再次檢視索引可以看到已新建了該索引。

3.2、查詢索引

import org.apache.http.HttpHost;

import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.client.indices.GetIndexResponse;

import java.io.IOException;

public class SearchIndex {
    public static void main(String[] args) throws IOException {
        // 建立客戶端物件
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));

        // 查詢索引 - 請求物件
        GetIndexRequest request = new GetIndexRequest("user2");
        // 傳送請求，獲取響應
        GetIndexResponse response = client.indices().get(request,
                RequestOptions.DEFAULT);
        
        System.out.println("aliases:"+response.getAliases());
        System.out.println("mappings:"+response.getMappings());
        System.out.println("settings:"+response.getSettings());

        client.close();
    }
}

響應如下：

3.3、刪除索引

import org.apache.http.HttpHost;
import org.elasticsearch.action.admin.indices.delete.DeleteIndexRequest;
import org.elasticsearch.action.support.master.AcknowledgedResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

import java.io.IOException;

public class DeleteIndex {
    public static void main(String[] args) throws IOException {
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));
        // 刪除索引 - 請求物件
        DeleteIndexRequest request = new DeleteIndexRequest("user2");
        // 傳送請求，獲取響應
        AcknowledgedResponse response = client.indices().delete(request,RequestOptions.DEFAULT);
        // 操作結果
        System.out.println("操作結果 ： " + response.isAcknowledged());
        client.close();
    }
}

響應如下：

4、文件操作

由於頻繁使用連線 Elasticsearch 和關閉它的程式碼，於是先對它進行重構。

package org.util;

import org.elasticsearch.client.RestHighLevelClient;

public interface ElasticsearchTask {
    void doSomething(RestHighLevelClient client) throws Exception;
}
package org.util;

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

public class ConnectElasticsearch{

    public static void connect(ElasticsearchTask task){
        // 建立客戶端物件
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));
        try {
            task.doSomething(client);
            // 關閉客戶端連線
            client.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4.1、新增文件

先建立一個實體類，如下：

package org.entity;

public class User {
    private String name; private Integer age; private String sex;

    public String getName() { return name; }
    public void setName(String name){ this.name = name; }
    public Integer getAge() {  return age; }
    public void setAge(Integer age) { this.age = age; }
    public String getSex() { return sex; }
    public void setSex(String sex) { this.sex = sex; }
}

新增文件：

package org.example;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.common.xcontent.XContentType;
import org.entity.User;
import org.util.ConnectElasticsearch;

public class InsertDoc {

    public static void main(String[] args) {
        ConnectElasticsearch.connect(client -> {
            // 新增文件 - 請求物件
            IndexRequest request = new IndexRequest();
            // 設定索引及唯一性標識
            request.index("user").id("1001");

            // 建立資料物件
            User user = new User();
            user.setName("zhangsan");
            user.setAge(30);
            user.setSex("男");

            ObjectMapper objectMapper = new ObjectMapper();
            String productJson = objectMapper.writeValueAsString(user);
            // 新增文件資料，資料格式為 JSON 格式
            request.source(productJson, XContentType.JSON);
            // 客戶端傳送請求，獲取響應物件
            IndexResponse response = client.index(request, RequestOptions.DEFAULT);
            //3.列印結果資訊
            System.out.println("_index:" + response.getIndex());
            System.out.println("_id:" + response.getId());
            System.out.println("_result:" + response.getResult());
        });
    }
}

輸出如下：

透過查詢文件也可以檢視到已經成功建立該文件。

4.2、修改文件

下面修改文件欄位值：

import org.elasticsearch.action.update.UpdateRequest;
import org.elasticsearch.action.update.UpdateResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.common.xcontent.XContentType;
import org.util.ConnectElasticsearch;

public class UpdateDoc {

    public static void main(String[] args) {
        ConnectElasticsearch.connect(client -> {
            // 修改文件 - 請求物件
            UpdateRequest request = new UpdateRequest();
            // 配置修改引數
            request.index("user").id("1001");
            // 設定請求體，對資料進行修改
            request.doc(XContentType.JSON, "sex", "女");
            // 客戶端傳送請求，獲取響應物件
            UpdateResponse response = client.update(request, RequestOptions.DEFAULT);
            System.out.println("_index:" + response.getIndex());
            System.out.println("_id:" + response.getId());
            System.out.println("_result:" + response.getResult());
        });
    }

}

輸出如下：

4.3、查詢文件

4.4、刪除文件

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