如何用Java操作Elasticsearch集群及引入官方Java Rest Client

Hey there! Great that you've got Elasticsearch up and running locally. Let's tackle your two questions clearly with practical, easy-to-follow examples:

1. How to add the official Elasticsearch Java Rest Client to your project #

First critical note: make sure the client version matches your Elasticsearch server version exactly—this avoids weird compatibility bugs. Here's how to set it up for common build tools:

For Maven projects #

Add these dependencies to your pom.xml:

<dependencies>
    <!-- Rest High Level Client (the user-friendly wrapper recommended for most use cases) -->
    <dependency>
        <groupId>org.elasticsearch.client</groupId>
        <artifactId>elasticsearch-rest-high-level-client</artifactId>
        <version>YOUR_ES_VERSION</version>
    </dependency>
    <!-- Core Elasticsearch dependency (required for client functionality) -->
    <dependency>
        <groupId>org.elasticsearch</groupId>
        <artifactId>elasticsearch</artifactId>
        <version>YOUR_ES_VERSION</version>
        <scope>provided</scope>
    </dependency>
</dependencies>

For Gradle projects #

Add these lines to your build.gradle (Groovy DSL):

dependencies {
    implementation 'org.elasticsearch.client:elasticsearch-rest-high-level-client:YOUR_ES_VERSION'
    implementation 'org.elasticsearch:elasticsearch:YOUR_ES_VERSION'
}

Replace YOUR_ES_VERSION with the version of your local Elasticsearch instance (e.g., 8.10.0 if that's what you installed).

2. Simple CRUD operations with Java #

We'll use the RestHighLevelClient (the most intuitive option for basic operations) for these examples. Let's start with setting up the client connection, then walk through each operation.

Step 1: Initialize the client #

We'll use try-with-resources to ensure the client closes automatically when we're done:

import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.apache.http.HttpHost;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.time.LocalDate;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexResponse;
import org.elasticsearch.action.get.GetRequest;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.action.update.UpdateRequest;
import org.elasticsearch.action.update.UpdateResponse;
import org.elasticsearch.action.delete.DeleteRequest;
import org.elasticsearch.action.delete.DeleteResponse;
import org.elasticsearch.xcontent.XContentType;

public class ElasticsearchCrudDemo {
    private static RestHighLevelClient createClient() {
        return new RestHighLevelClient(
                RestClient.builder(
                        new HttpHost("localhost", 9200, "http")));
    }

    public static void main(String[] args) {
        try (RestHighLevelClient client = createClient()) {
            // Run CRUD operations in sequence
            indexDocument(client);
            getDocument(client);
            updateDocument(client);
            deleteDocument(client);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Step 2: Index a new document #

This adds a document to an index (the index will be created automatically if it doesn't exist):

private static void indexDocument(RestHighLevelClient client) throws IOException {
    // Define document content as a map (you can also use a JSON string)
    Map<String, Object> book = new HashMap<>();
    book.put("title", "Elasticsearch for Java Developers");
    book.put("author", "Jane Smith");
    book.put("publish_date", LocalDate.now().toString());
    book.put("pages", 320);

    IndexRequest request = new IndexRequest("books") // Name of your index
            .id("1") // Optional: Elasticsearch generates a random ID if you omit this
            .source(book, XContentType.JSON);

    IndexResponse response = client.index(request, org.elasticsearch.client.RequestOptions.DEFAULT);
    System.out.println("Index result: " + response.getResult());
}

Step 3: Retrieve a document #

Fetch the document we just added:

private static void getDocument(RestHighLevelClient client) throws IOException {
    GetRequest request = new GetRequest("books", "1"); // Index name + document ID
    GetResponse response = client.get(request, org.elasticsearch.client.RequestOptions.DEFAULT);

    if (response.isExists()) {
        System.out.println("Retrieved document: " + response.getSourceAsString());
    } else {
        System.out.println("Document not found!");
    }
}

Step 4: Update a document #

Modify specific fields of the existing document:

private static void updateDocument(RestHighLevelClient client) throws IOException {
    UpdateRequest request = new UpdateRequest("books", "1");
    // Update the page count and add a new rating field
    Map<String, Object> updates = new HashMap<>();
    updates.put("pages", 345);
    updates.put("rating", 4.7);
    request.doc(updates, XContentType.JSON);

    UpdateResponse response = client.update(request, org.elasticsearch.client.RequestOptions.DEFAULT);
    System.out.println("Update result: " + response.getResult());
}

For more complex updates (like incrementing a number field), you can use Elasticsearch scripts instead of a simple field map.

Step 5: Delete a document #

Remove the document from the index:

private static void deleteDocument(RestHighLevelClient client) throws IOException {
    DeleteRequest request = new DeleteRequest("books", "1");
    DeleteResponse response = client.delete(request, org.elasticsearch.client.RequestOptions.DEFAULT);
    System.out.println("Delete result: " + response.getResult());
}
}

Quick notes #

• If you've enabled Elasticsearch security (username/password auth) on your local instance, you'll need to add credentials to the client builder using an HttpClientConfigCallback.
• In production code, replace the stack trace print with proper error handling (e.g., logging, user-friendly messages).

内容的提问来源于stack exchange，提问作者D vignesh