How do you create a custom index for an Elasticsearch entity?

Table of Contents

• Introduction
  • 1. Define the Entity Class with **@Document** Annotation
    • Example: Defining the Entity
    • Key Elements:
  • 2. Customize Index Mappings
    • Custom Field Mappings with @Field
  • 3. Manually Create a Custom Index with Settings and Mappings
    • Example: Programmatically Creating an Index with Custom Settings and Mappings
  • 4. Define Custom Settings and Mappings in the **application.yml** or **application.properties**
    • Example: Custom Settings in application.yml
  • 5. Create Elasticsearch Repository for Custom Index
    • Example: Custom Repository for Product Entity
  • 6. Test Custom Index Creation
    • Example: Adding Products and Testing Custom Index
• Conclusion

Introduction

Elasticsearch allows you to store and retrieve documents in an index, and each index can have custom configurations to optimize search and indexing performance. In Spring Boot with Spring Data Elasticsearch, you can define a custom index for your entities by specifying the index name and further customizing the index settings and mappings. This enables more control over how documents are indexed and searched in Elasticsearch.

This guide will show you how to create a custom index for an Elasticsearch entity in a Spring Boot application, including defining custom index settings, mappings, and associating the entity with the index.

1. Define the Entity Class with **@Document** Annotation

To define a custom index for an entity, you need to annotate the entity class with the @Document annotation. You can specify the index name and other properties to customize the Elasticsearch index behavior.

Example: Defining the Entity

Key Elements:

• **@Document(indexName = "custom_products")**: Defines the custom index name (custom_products) for the Product entity.
• **createIndex = true**: Tells Elasticsearch to create the index automatically when the application starts (default behavior is true).
• **shards = 3, replicas = 2**: Specifies custom settings for the index, defining 3 shards and 2 replicas.

2. Customize Index Mappings

Elasticsearch mappings define how fields are indexed and stored in the index. You can customize field mappings using annotations like @Field in Spring Data Elasticsearch, or you can define additional custom settings and mappings manually.

Custom Field Mappings with @Field

In the entity class, you can use the @Field annotation to specify how each field should be indexed. This is useful for customizing the data types and analyzers for each field.

• **@Field(type = FieldType.Text)**: Specifies that the field is of type Text and should be analyzed.
• **analyzer = "standard"**: Specifies the analyzer to use when indexing this field (e.g., the standard analyzer).

3. Manually Create a Custom Index with Settings and Mappings

If you need to apply more advanced index settings or mappings, you can use the ElasticsearchRestTemplate or ElasticsearchOperations to create the index programmatically. This allows you to specify custom settings, analyzers, and other configurations not possible with annotations alone.

Example: Programmatically Creating an Index with Custom Settings and Mappings

In this example:

• **ElasticsearchRestTemplate**: Provides methods for interacting with Elasticsearch.
• **indexOps(Product.class)**: Retrieves the index operations for the Product class.
• **create()**: Creates the custom index.
• **putMapping()**: Applies the custom mappings to the index.

4. Define Custom Settings and Mappings in the **application.yml** or **application.properties**

While the primary way to define a custom index is through annotations and programmatically, you can also define default settings for Elasticsearch in your application.yml or application.properties file.

Example: Custom Settings in application.yml

In this configuration:

• **number_of_shards**: Defines the number of primary shards for the custom index.
• **number_of_replicas**: Defines the number of replica shards.

5. Create Elasticsearch Repository for Custom Index

Once the entity is annotated with @Document and the index is created, you can create a repository to interact with the custom index. The repository extends ElasticsearchRepository and provides basic CRUD operations and query methods.

Example: Custom Repository for Product Entity

This repository:

• Defines the basic CRUD operations for the Product entity.
• Adds a custom method findByNameContaining to search for products by name using full-text search.

6. Test Custom Index Creation

Once your index is created and configured, you can test it by adding a few products to the Elasticsearch index and verifying the index structure.

Example: Adding Products and Testing Custom Index

Conclusion

Creating a custom index for an Elasticsearch entity in Spring Boot is straightforward, whether you're configuring it via annotations, programmatically, or using a combination of both. The @Document annotation allows you to specify the index name and custom settings, such as the number of shards and replicas. You can further customize mappings for each field in the entity, and even define advanced index settings via ElasticsearchRestTemplate.

By properly setting up custom indices and mappings, you ensure that your data is stored in Elasticsearch in the most efficient way possible, which improves the performance and scalability of your search operations.