Elasticsearch in Java Applications

Elasticsearch is a distributed, free, and public search and analytics engine, that works with all kinds of data, including numerical, textual, geographic, structured, and unstructured. Elasticsearch is lightweight. Elasticsearch has a total dependence size of only about 300 KB. It is just concerned with query performance. This indicates that all database-related processes are well-optimized and scalable. This system has a very high fault tolerance. When one Elasticsearch node in a cluster fails, the master server quickly determines the problem and sends incoming requests as quickly as it can to a replacement node.

How to Use Elasticsearch in Java Applications

Below are the steps to use Elasticsearch in our Java applications.

Prerequisites:

First launch an Elasticsearch instance:

docker run -d --name elastic-test -p 9200:9200 -e "discovery.type=single-node" 
-e "xpack.security.enabled=false" docker.elastic.co/elasticsearch/elasticsearch:8.9.3

Elasticsearch by default watches the 9200 port for incoming HTTP requests. By launching a preferred browser and visiting http://localhost:9200/, we can confirm that it has been started successfully:

{
  "name": "238170191b08",
  "cluster_name": "elasticsearch",
  "cluster_uuid": "pvHXz7xsS5W4zlZiiATelw",
  "version": {
    "number": "6.1.4",
    "build_hash": "5b1fea5",
    "build_date": "2024-01-12T01:27:58.208Z",
    "build_snapshot": false,
    "lucene_version": "7.1.0",
    "minimum_wire_compatibility_version": "5.6.0",
    "minimum_index_compatibility_version": "5.1.0"
  },
  "tagline": "You Know, for Search"
}

Step 1: Add Maven Dependencies

Let's get right to the Java client now that our main Elasticsearch cluster is operational.Elasticsearch and the Jackson library must first be included to our pom.xml file:

<dependency>
    <groupId>org.elasticsearch</groupId>
    <artifactId>elasticsearch</artifactId>
    <version>8.9.4</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.16.4</version>
</dependency>

Step 2: Elasticsearch Java Client

We can now communicate with Elasticsearch. We will then examine how to carry out the most typical tasks, such adding a document to an index, removing a document from an index, and looking up documents inside an index.

RestClient restClient = RestClient
  .builder(HttpHost.create("http://localhost:9200"))
  .build();
ElasticsearchTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());
ElasticsearchClient client = new ElasticsearchClient(transport);

Step 3: Document Indexing

Adding data to Elastic is the first step towards making them searchable. We'll utilize the ElasticseachClient's.index() function for this:

Person person = new Person(30, "dido datta", new Date(1771468076764L));
IndexResponse response = client.index(i -> i
  .index("person")
  .id(person.getFullName())
  .document(person));

Step 4: Indexed Document Queries

The SearchResponse returned by the.search() function contains Hits. The HitsMetadata can be obtained from the SearchResponse object, and then we can acquire the hits by using the.hits() method once again to receive a List of all the Person objects that match the search request.

String searchText = "Rik";
SearchResponse<Person> searchResponse = client.search(s -> s
  .index("person")
  .query(q -> q
    .match(t -> t
      .field("fullName")
      .query(searchText))), Person.class);

List<Hit<Person>> hits = searchResponse.hits().hits();
assertEquals(1, hits.size());
assertEquals("Rik Datta", hits.get(0).source().getFullName());

Step 5: Getting Specific Documents by ID

Given a document's id, our goal is to retrieve it first, then remove it. To obtain documents, for example, we utilize the get() method:

String documentId = "Rik Datta";
GetResponse<Person> getResponse = client.get(s -> s
  .index("person")
  .id(documentId), Person.class);
Person source = getResponse.source();
assertEquals("Rik Datta", source.getFullName());

Step 6: Erasing Specific Documents by ID

Remove a document from an index using the delete() method:

String documentId = dido ";
DeleteResponse response = client.delete(i -> i
  .index("person")
  .id(documentId));
assertEquals(Result.Deleted, response.result());
assertEquals(" dido datta", response.id());

Step 7: Running the application

Now, let us run the application by performing all the above mentioned operations.

public static void main(String[] args) throws IOException 
{
    makeConnection();
     
      // Creating a New Person Instance
    System.out.println("Inserting a new Person with name Shubham...");
    Person person = new Person();
    person.setName("Shubham");
  
    person = insertPerson(person);
    System.out.println("Person inserted --> " + person);
     
      // Updating the Name of Person
    System.out.println("Changing name to `Rik Datta`...");
    person.setName("Rik Datta");
  
      // Update Person on the Database
    updatePersonById(person.getPersonId(), person);
    System.out.println("Person updated  --> " + person);
 
      // Getting Person on the Database 
    System.out.println("Getting Rik...");
    Person personFromDB = getPersonById(person.getPersonId());
    System.out.println("Person from DB  --> " + personFromDB);
 
      // Deleting Person from the Database
    System.out.println("Deleting Rik...");
    deletePersonById(personFromDB.getPersonId());
    System.out.println("Person Deleted");
 
    closeConnection();
}

Output:

Below in the output we have performed all the insert, update, and delete operations.