elasticsearchHow do I use Elasticsearch with Java?

Elasticsearch is a popular open-source search engine built on Apache Lucene. It enables you to store, search, and analyze big volumes of data quickly and in near real-time.

Using Elasticsearch with Java requires three steps:

1. Install the Elasticsearch Java client: Add the following dependency to your project's pom.xml file:

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.6.2</version>
</dependency>

2. Create an instance of the client:

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

3. Use the client to perform operations:

SearchRequest searchRequest = new SearchRequest("posts");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.matchQuery("title", "java"));
searchRequest.source(searchSourceBuilder);

SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
SearchHits hits = searchResponse.getHits();

System.out.println("Total hits: " + hits.getTotalHits());
for (SearchHit hit : hits.getHits()) {
    System.out.println(hit.getSourceAsString());
}

Output example

Total hits: 2
{"title": "Java 8 Streams", "content": "Java 8 Streams..."}
{"title": "Java 11 Features", "content": "Java 11 Features..."}

The code above creates an instance of the client, then uses it to perform a search request on the posts index. The search query looks for documents with the title containing the word java. The output of the code prints out the total number of hits and the source of each document that matched the query.

Helpful links

• Elasticsearch Java Client
• Query Builders

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