SpringBoot整合ElasticSearch

1、選型

Java操作ElasticSearch有兩種方式，一個是通過ES的9300端口使用TCP的方式操作，另一種是通過ES的9200端口使用HTTP的方式

1）9300 TCP

spring-data-elasticsearch:transport-api.jar

• springboot 版本不同， transport-api.jar 不同，不能適配 es 版本

• 7.x 已經不建議使用，8 以后就要廢棄

2）9200 HTTP

• JestClient：非官方，更新慢

• RestTemplate：模擬發 HTTP 請求，ES 很多操作需要自己封裝，麻煩

• HttpClient：同上

• Elasticsearch-Rest-Client：官方 RestClient，封裝了 ES 操作，API 層次分明，上手簡單

綜上所述，選擇Elasticsearch-Rest-Client（elasticsearch-rest-high-level-client）是最優的選擇，下面記錄如何整合

Elasticsearch-Rest-Client 官方文檔
https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high.html

2、SpringBoot整合

1）引入依賴

<properties>
    <java.version>1.8</java.version>
    //注意es版本
    <elasticsearch.version>7.4.2</elasticsearch.version> 
</properties>
    
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.4.2</version>
</dependency>

2）編寫配置類

@Configuration
public class ElasticSearchConfig {

    public static final  RequestOptions COMMON_OPTIONS;

    static {
        // RequestOptions類保存了請求的部分，這些部分應該在同一個應用程序中的許多請求之間共享。
        // 創建一個singqleton實例，並在所有請求之間共享它。可以設置請求頭之類的一些配置
        RequestOptions.Builder builder = RequestOptions.DEFAULT.toBuilder();
        // builder.addHeader("Authorization", "Bearer " + TOKEN);
        // builder.setHttpAsyncResponseConsumerFactory(
        //         new HttpAsyncResponseConsumerFactory
        //                 .HeapBufferedResponseConsumerFactory(30 * 1024 * 1024 *1024));
        COMMON_OPTIONS = builder.build();
    }
	//創建ES實例
    @Bean
    public RestHighLevelClient restHighLevelClient(){
        return new RestHighLevelClient(RestClient.builder(new HttpHost(
                "192.168.XX.XXX",9200,"http"
        )));
    }

}

RequestOptions更多配置參考
https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-low-usage-requests.html#java-rest-low-usage-request-options
//創建ES實例參考
https://www.elastic.co/guide/en/elasticsearch/client/java-rest/master/java-rest-low-usage-initialization.html

3）測試檢索

① 測試保存

@SpringBootTest
class SearchApplicationTests {

    @Autowired
    RestHighLevelClient restHighLevelClient;

    @Test
    void contextLoads() throws IOException {
    	//測試保存
        IndexRequest request = new IndexRequest("posts");
        request.id("1");
        String jsonString = "{" +
                "\"user\":\"kimchy\"," +
                "\"postDate\":\"2013-01-30\"," +
                "\"message\":\"trying out Elasticsearch\"" +
                "}";
        request.source(jsonString, XContentType.JSON);
        IndexResponse index=
        restHighLevelClient.index(request,ElasticSearchConfig.COMMON_OPTIONS);
        System.out.println("index-------------:"+ index);
    }
}

② 測試復雜檢索

測試在Elastic進階檢索中使用kibana寫的案例

參考ElasticSearchAPI

https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high-search.html

#搜索address中包含 mill的所有人的年齡分布以及平均年齡
 @Test
    void test() throws IOException {
        //搜索address中包含 mill的所有人的年齡分布以及平均年齡
        //  創建檢索請求
        SearchRequest searchRequest = new SearchRequest();
        // 指定索引
        searchRequest.indices("bank");
        // 指定 DSL 檢索條件
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        // 構建檢索條件 address 包含 mill
        searchSourceBuilder.query(QueryBuilders.matchQuery("address","mill"));
        // 按照年齡值分布進行聚合
        TermsAggregationBuilder ageAgg  = AggregationBuilders.terms("ageAgg").field("age").size(10);
        searchSourceBuilder.aggregation(ageAgg);
        // 1.3 計算平均薪資
        AvgAggregationBuilder  balanceAvg = AggregationBuilders.avg("balanceAvg").field("balance");
        searchSourceBuilder.aggregation(balanceAvg);

        System.out.println("檢索條件："+searchSourceBuilder.toString());
        searchRequest.source(searchSourceBuilder);

        //執行檢索
        SearchResponse searchResponse = restHighLevelClient.search(searchRequest, ElasticSearchConfig.COMMON_OPTIONS);

        //獲取查詢到的記錄
        SearchHits hits = searchResponse.getHits();

        SearchHit[] searchHits = hits.getHits();

        //獲取檢索的分析信息
        Aggregations aggregations = searchResponse.getAggregations();
        // for (Aggregation aggregation : aggregations.asList()) {
        //     System.out.println("當前聚合名：" + aggregation.getName());
        // }
        Terms ageAgg1 = aggregations.get("ageAgg");
        for (Terms.Bucket bucket : ageAgg1.getBuckets()) {
            String keyAsString = bucket.getKeyAsString();
            System.out.println("年齡：" + keyAsString + " 歲的有 " + bucket.getDocCount() + " 人");
        }

        Avg balanceAvg1 = aggregations.get("balanceAvg");
        System.out.println("平均薪資: " + balanceAvg1.getValue());

  }