How do you configure data sources in Spring Boot?

Table of Contents

• Introduction
• Configuring a Single Data Source in Spring Boot
  • Example using application.properties
  • Example using application.yml
• Configuring Multiple Data Sources
  • Step 1: Define Properties for Multiple Data Sources
  • Step 2: Create Configuration Classes for Each Data Source
    • Primary Data Source Configuration
    • Secondary Data Source Configuration
  • Step 3: Inject Data Sources and Use Them
• Configuring Data Source Connection Pool (HikariCP)
  • Example configuration:
• Conclusion

Introduction

In Spring Boot, configuring a data source is a critical step for setting up database connections, whether you are using JDBC, JPA (Java Persistence API), or Spring Data. Spring Boot simplifies data source configuration through auto-configuration, but it also provides extensive options for customizing your data source settings. In this guide, we will discuss how to configure data sources in Spring Boot applications, set up multiple data sources, and integrate with JDBC, JPA, and HikariCP (the default connection pool in Spring Boot).

Configuring a Single Data Source in Spring Boot

Spring Boot's auto-configuration mechanism makes it very easy to set up a single data source by simply defining the necessary properties in your application.properties or application.yml file. Spring Boot automatically configures the data source based on these properties.

Example using application.properties

• **spring.datasource.url**: The JDBC URL of your database.
• **spring.datasource.username** and **spring.datasource.password**: Credentials for your database.
• **spring.datasource.driver-class-name**: The fully qualified name of the JDBC driver (Spring Boot can auto-detect it in most cases).
• **spring.datasource.jpa.hibernate.ddl-auto**: Controls the Hibernate DDL mode (e.g., create, update, validate, none).
• **spring.datasource.jpa.hibernate.show-sql**: Whether to display SQL queries in the log.

Spring Boot will automatically detect the spring.datasource properties and configure a HikariCP connection pool by default. HikariCP is a high-performance connection pool used in Spring Boot for managing database connections.

Example using application.yml

Configuring Multiple Data Sources

Spring Boot also supports multiple data sources. For example, you might have one data source for your primary database and another for a reporting or analytics database. To configure multiple data sources, you'll need to define each data source separately and explicitly create DataSource, EntityManagerFactory, and TransactionManager beans for each source.

Step 1: Define Properties for Multiple Data Sources

You can define multiple data source properties in application.properties or application.yml.

Step 2: Create Configuration Classes for Each Data Source

You need to create a separate configuration class for each data source.

Primary Data Source Configuration

Secondary Data Source Configuration

Step 3: Inject Data Sources and Use Them

Now, you can inject the primary and secondary data sources in your service classes.

Configuring Data Source Connection Pool (HikariCP)

Spring Boot uses HikariCP as the default connection pool. You can configure its settings in application.properties or application.yml.

Example configuration:

• **spring.datasource.hikari.connection-timeout**: Maximum number of milliseconds that the pool will wait for a connection to be established.
• **spring.datasource.hikari.maximum-pool-size**: The maximum number of connections in the pool.
• **spring.datasource.hikari.minimum-idle**: The minimum number of idle connections that HikariCP tries to maintain.
• **spring.datasource.hikari.idle-timeout**: The maximum amount of time a connection can sit idle in the pool.
• **spring.datasource.hikari.max-lifetime**: The maximum lifetime of a connection before it is retired.

Conclusion

Configuring data sources in Spring Boot is simple and flexible, with Spring Boot automatically handling most configuration tasks through auto-configuration. For a single data source, you only need to define a few properties in the application.properties or application.yml file. When working with multiple data sources, you need to configure each one separately and define the necessary DataSource, EntityManagerFactory, and TransactionManager beans.

Spring Boot also integrates seamlessly with HikariCP, providing a high-performance connection pool that can be customized to meet the needs of your application. Whether you are using JDBC, JPA, or Spring Data, configuring data sources in Spring Boot is a straightforward process that ensures your application can interact with databases effectively and efficiently.