Elasticsearch with Spring Boot + Spring Data

Carvia Tech | November 18, 2020 | | 14 views


In this article, we will discuss how to configure & use Elasticsearch Engine with Spring Boot & Spring Data using High Level REST Client provided by Elasticsearch.

Prerequisites

  • Java 8 or 11

  • Gradle

  • Elasticsearch 7.10

  • Spring Boot 2.4.0

  • Spring Data 4.1

Elasticsearch

Elasticsearch is an open source, distributed full-text search engine that provides REST api for indexing, searching etc. The major components of elasticsearch are:

Document

Documents are JSON objects that are stored within an Elasticsearch index and are considered as the base unit of storage.

Index

An index is like a database in a relational database. It has mapping which defines the type of document. An index maps to one or more primary shards and can have zero or more replica shards.

Shard

Horizontally splits an index to distribute data around the cluster. The more the size of index, more shards are generally needed for its optimal performance. In Lucene terminology, Shard is a single Lucene index which contains part of documents from an Elasticsearch Index.

Replica

Copy of index’s shard is known as replica, it is mainly fail-safe mechanism of Elasticsearch. This acts as a backup when a node crashes. Replicas also serve read requests, so adding replicas can help to increase search performance.

You need to make sure that Elasticsearch is up and running locally on port 9200, using the below command:

curl -XGET "http://localhost:9200"

Gradle dependencies

First step is to create a Spring Boot application, you can do so by visiting https://start.spring.io

build.gradle
plugins {
    id "java"
    id 'org.springframework.boot' version "2.4.0"
    id "io.spring.dependency-management" version "1.0.10.RELEASE"
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("org.springframework.boot:spring-boot-starter-data-elasticsearch")   (1)
}
1 Spring data elasticsearch module

Elasticsearch configuration

Spring Boot 2.4.0 does not require any special configuration for ElasticSearch, as everything is taken care by ElasticsearchRestClientAutoConfiguration configuration class. We just need to provide the below configuration in application yal to trigger the automatic bean creation:

application.yml
spring.elasticsearch.rest.uris: http://localhost:9200
spring.elasticsearch.rest.username: <username>
spring.elasticsearch.rest.password: <password>

Since TransportClient is deprecated in favour of High Level REST Client, we will not discuss TransportClient in this article.

If you want to customize the elastic search configuration, you can provide a bean of type …​. TODO…​

Java implementation

We need to create a main class for running spring boot application, model classes for Spring data elasticsearch, repository and service classes.

Entity class

Book.java - A sample Book entity.
@Document(indexName="books")
class Book {
    @Id
    private String id;
    @Field(type = FieldType.text)
    private String name;
    @Field(type = FieldType.text)
    private String summary;
    @Field(type = FieldType.Integer)
    private Integer price;
	// getter/setter ...
}

Repository class

We need to define a domain class-specific repository interface for each entity. Typically, your repository interface extends Repository, CrudRepository, PagingAndSortingRepository or ElasticsearchRepository. ElasticsearchRepository interface extends PagingAndSortingRepository, thus enabling built in support for paging and sorting.

BookRepository.java - Repository interface
public interface BookRepository extends ElasticsearchRepository<Book, String> {

    Page<Book> findByName(String name, Pageable pageable);
}

Service layer

Spring data Elasticsearch auto-creates indexes based on the domain mapping. But we can create indexes manually too using ElasticsearchTemplate.

In this class we will explore:

  • Creating indexes manually

  • Indexing a document

  • Searching/paging documents

  • Updating a document

  • Deleting a document

  • Adding a custom method to repository

  • Partial updates to document

BookService.java
@Service
class BookService {

    @Autowired
    BookRepository bookRepository;

    @Autowired
    ElasticsearchTemplate elasticsearchTemplate;

    public void createIndex() {
        elasticsearchTemplate.indexOps(Book.class).create();
    }

    public void create() {
        Book book = new Book();
        bookRepository.save(book);
    }
}

Spring Boot App

We need to create a main class that will bootstrap the spring container using a main method. This is the entrypoint for our spring boot application.

Main Application
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ElasticApp {

    public static void main(String[] args) {
        SpringApplication.run(Myapplication.class, args);
    }
}

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