使用Jest查詢Elasticsearch

摘要： 近期需要在專案中將Elasticsearch查詢由Python切換到Java才可以在公司的專案中正常使用,而且專案使用的還是Java7的版本,而預設的Elasticsearch需要Java8的支援,只好降級處理了。 這裡我們的demo,使用的Elasticsearch版本是...

近期需要在專案中將Elasticsearch查詢由Python切換到Java才可以在公司的專案中正常使用,而且專案使用的還是Java7的版本,而預設的Elasticsearch需要Java8的支援,只好降級處理了。

這裡我們的demo,使用的Elasticsearch版本是6.3.1 ,對應的Java版本為8,我們使用Jest庫來簡化操作。

首先使用maven下載對應的依賴庫:

<?xml version="1.0"?>
<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">
<modelVersion>4.0.0</modelVersion>
<groupId>com.es</groupId>
<artifactId>es</artifactId>
<version>1.0</version>
<dependencies>
<dependency>
<groupId>io.searchbox</groupId>
<artifactId>jest</artifactId>
<version>6.3.1</version>
</dependency>
</dependencies>
</project>

在這個過程中,我們需要配置對應maven源為國內的阿里雲,不然其下載速度不堪入目。

我們修改maven配置檔案settings.xml 中mirrors中的節點,新增如下程式碼:

<mirror>
<id>nexus-aliyun</id>
<mirrorOf>central</mirrorOf>
<name>Nexus aliyun</name>
<url>http://maven.aliyun.com/nexus/content/groups/public</url>
</mirror>

接著我們下載對應的依賴包:

mvn dependency:copy-dependencies -DoutputDirectory=libs

在這裡,我們設定其下載目錄為當前目錄下libs目錄,接著maven就會幫我們自動下載對應的包了。

下面我們開始編寫我們的程式,1個非常簡單的程式:

import java.io.IOException;
import java.util.*;
import java.util.Objects;
import com.google.gson.GsonBuilder;
import io.searchbox.client.*;
import io.searchbox.core.*;
import io.searchbox.client.config.*;

public class ESClient {
private static final String ES_HOST = "http://127.0.0.1";
private static final int ES_HTTP_PORT = 9200;
private static JestClient client;

public static synchronized JestClient getClient(){
if(client==null){
build();
}
return client;
}

public static void close(JestClient client){
if(!Objects.isNull(client)){
try{
client.close();
}catch (Exception e){
e.printStackTrace();
}
}
}

private static void build() {
JestClientFactory factory = new JestClientFactory();
//例項化客戶端工廠類
factory.setHttpClientConfig(new HttpClientConfig.Builder(ES_HOST+":"+ES_HTTP_PORT)
.multiThreaded(true)
.defaultMaxTotalConnectionPerRoute(2)
.maxTotalConnection(2) //設定總連線數為2個
.connTimeout(10000) //設定連線超時時間
.readTimeout(10000)//設定讀取超時時間
.gson(new GsonBuilder().setDateFormat("yyyy-MM-dd HH:mm:ss").create()) //設定JSON日期格式
.build());
client = factory.getObject();
}

public static void main(String[] args) throws IOException {
JestClient client = getClient();
String query = "{\"query\":{\"match_all\":{}}}";
Search.Builder searchBuilder = new Search.Builder(query).addIndex("demo").addType("person");
SearchResult result = client.execute(searchBuilder.build());
System.out.println(result.toString());
}
}

在這裡,匯入對應的包,主要是下面這3行程式碼:

import io.searchbox.client.*;
import io.searchbox.core.*;
import io.searchbox.client.config.*;

在方法build中,我們例項化1個JestClientFactory 類,之後進行對應的配置,最後通過其工廠類的getObject 得到對應的客戶端物件。

而在main入口中,我們通過getClient 方法得到對應的例項後,之後構建1個JSON字串,之後呼叫Search.Builder 對JSON字串進行構建,並新增對應的Index和DocType後,我們通過客戶端例項的execute方法來執行,最後通過其查詢的結果轉換為字串即可。

其結果如下:

dog@debian:~/es$ javac -classpath ".:libs/*" ESClient.java
dog@debian:~/es$ java -classpath ".:libs/*" ESClient
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Result: {"took":7,"timed_out":false,"_shards":{"total":5,"successful":5,"skipped":0,"failed":0},"hits":{"total":5,"max_score":1.0,"hits":[{"_index":"demo","_type":"person","_id":"1g3l82UB8TY7aIKswO1s","_score":1.0,"_source":{"username":"王五","gender":"男","age":"21","region":"杭州","tags":["吃貨","技術大牛"]}},{"_index":"demo","_type":"person","_id":"1A3l82UB8TY7aIKsvu2-","_score":1.0,"_source":{"username":"張三","gender":"男","age":"20","region":"中山","tags":["吃貨","宅男"]}},{"_index":"demo","_type":"person","_id":"1Q3l82UB8TY7aIKswO0f","_score":1.0,"_source":{"username":"李四","gender":"男","age":"25","region":"金華","tags":["宅男","技術大牛"]}},{"_index":"demo","_type":"person","_id":"2A3l82UB8TY7aIKswe0G","_score":1.0,"_source":{"username":"熊莎莎","gender":"女","age":"25","region":"河源","tags":["吃貨","中二"]}},{"_index":"demo","_type":"person","_id":"1w3l82UB8TY7aIKswO2-","_score":1.0,"_source":{"username":"莫曉佳","gender":"女","age":"23","region":"蘇州","tags":["麥霸","吃貨"]}}]}}, isSucceeded: true, response code: 200, error message: null

這個過程不得不說還是有點問題的,由於專案比較趕,於是趁早起的時候編寫了上述程式碼,走了不少彎路,還是有不足了。只能等上班再進行完善了。