Elasticsearch Rest High Level Client

昨天折腾了一下Elasticsearch, 今天把过程记录下来免得忘记。

首先当然是安装，我用的mac, 所以安装很简单:

brew tap elastic/tap
brew install elastic/tap/elasticsearch-full
elasticsearch

搞定。

然后就是按照官方的教程, 用curl把这几个页面上(index, search, aggregations)的命令跑了一遍。 为了免得以后重新打命令，我把这个命令都放到一个reference.sh里面去了，想要跑哪一行，就把那个命令前面的#去掉，然后bash reference.sh就可以了。

最后还折腾了一下官方的Java REST Client 7.4, 其中有一个坑就是Maven Repository页面上写的是7.4.1，但是我在pom.xml里面用7.4.1死活编译不了，我还以为是因为我用了阿里云的maven源，里面没有更新，换成官方的源还是不行，我去官方的源上一看，到今天(2019-10-23)为止, 官方源上最新的版本是7.4.0，所以上面应该写7.4.0.

其它的就没什么了，先搞个project:

mvn -B archetype:generate -DarchetypeGroupId=org.apache.maven.archetypes -DgroupId=com.laogongshuo.es -DartifactId=elasticsearch
cd elasticsearch

然后把依赖关系加到pom.xml里面去:

<properties>
	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	<maven.compiler.encoding>UTF-8</maven.compiler.encoding>
	<java.version>1.8</java.version>
	<maven.compiler.source>1.8</maven.compiler.source>
	<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<dependencies>
	<dependency>
		<groupId>org.elasticsearch.client</groupId>
		<artifactId>elasticsearch-rest-high-level-client</artifactId>
		<version>7.4.0</version>
	</dependency>
</dependencies>

在src/main/java/com/laogongshuo/es/App.java里面撸一些代码:

package com.laogongshuo.es;

import java.io.IOException;
import org.apache.http.HttpHost;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.builder.SearchSourceBuilder;

public class App {

  private static final String[] FETCH_FIELDS = {
    "account_number",
    "balance",
    "firstname",
    "lastname",
    "age",
    "gender",
    "address",
    "employer",
    "email",
    "city",
    "state"
  };

  public static void matchAll() throws IOException {
    RestHighLevelClient client =
        new RestHighLevelClient(RestClient.builder(new HttpHost("localhost", 9200, "http")));
    SearchRequest searchRequest = new SearchRequest("bank");
    SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
    searchSourceBuilder.query(QueryBuilders.matchAllQuery());
    searchRequest.source(searchSourceBuilder);

    SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
    if (searchResponse.getHits().getTotalHits().value > 0) {
      System.out.println(searchResponse.getHits().getTotalHits());
      for (SearchHit hit : searchResponse.getHits()) {
        System.out.println("Match: ");
        for (String fetchField : FETCH_FIELDS) {
          System.out.println(" - " + fetchField + " " + hit.getSourceAsMap().get(fetchField));
        }
      }
    } else {
      System.out.println("No results matching the criteria.");
    }
    client.close();
  }

  public static void search() throws IOException {
    RestHighLevelClient client =
        new RestHighLevelClient(RestClient.builder(new HttpHost("localhost", 9200, "http")));
    SearchRequest searchRequest = new SearchRequest("bank");
    SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
    sourceBuilder.query(QueryBuilders.termQuery("account_number", "49"));
    searchRequest.source(sourceBuilder);

    SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
    if (searchResponse.getHits().getTotalHits().value > 0) {
      System.out.println(searchResponse.getHits().getTotalHits());
      for (SearchHit hit : searchResponse.getHits()) {
        System.out.println("Match: ");
        for (String fetchField : FETCH_FIELDS) {
          System.out.println(" - " + fetchField + " " + hit.getSourceAsMap().get(fetchField));
        }
      }
    } else {
      System.out.println("No results matching the criteria.");
    }
    client.close();
  }

  public static void main(String[] args) throws IOException {
    matchAll();
    search();
  }
}

最后编译运行：

mvn clean package
mvn exec:java -Dexec.mainClass="com.laogongshuo.es.App"

因为没有在pom.xml里面写执行的mainClass，所以只能这么跑，不过能看到结果就行了。

文中全部代码都在这里，github, 欢迎star.