How do you customize the application.properties file in Spring Boot?

Table of Contents

Introduction

In Spring Boot, the application.properties file (or application.yml) is a central place for configuring application settings such as database connections, server ports, logging levels, and much more. By customizing this file, you can adjust various aspects of your Spring Boot application without writing complex code. In this guide, we will explore how to customize the application.properties file in Spring Boot, understand the structure, and manage different configuration scenarios effectively.

Understanding the application.properties File

The application.properties file is a simple key-value pair configuration file used to define various properties in a Spring Boot application. By default, Spring Boot looks for this file in the src/main/resources directory of your project. The application.properties file allows you to configure application-wide settings that Spring Boot will automatically pick up and apply.

Example of a basic application.properties file:

In this example:

• server.port sets the HTTP server’s port.
• spring.datasource.* configures the database connection.
• logging.level.* adjusts the logging level for Spring components.

Customizing Common Application Properties

1. Changing the Server Port

One of the most common customizations is changing the server port. By default, Spring Boot runs on port 8080, but you can change it easily in the application.properties file.

Example:

This will start your application on port 9090 instead of the default 8080.

2. Database Configuration

Spring Boot makes it easy to configure database settings like the URL, username, password, and driver. You can customize the spring.datasource properties to suit your database needs.

Example:

• spring.datasource.url: Specifies the database URL.
• spring.datasource.username and spring.datasource.password: Define the database credentials.
• spring.jpa.hibernate.ddl-auto: Specifies how Hibernate should manage the schema (e.g., create, update, none).

3. Logging Configuration

You can control the verbosity of logs generated by Spring Boot and other components using the logging.level property.

Example:

• logging.level.org.springframework.web=DEBUG: Sets the logging level for Spring MVC components to DEBUG.
• logging.level.com.myapp=INFO: Sets the logging level for your application’s package to INFO.

4. Configuring Spring Profiles

Spring Boot allows you to define different configurations for different environments using profiles (e.g., dev, prod, test). Profiles can be specified in the application.properties file to adjust settings depending on the environment.

Example: Setting Active Profile

This tells Spring Boot to use the properties defined in the application-dev.properties file (if present).

Example: Profile-Specific Properties

You can create separate property files for different profiles. For example, you can have application-dev.properties, application-prod.properties, and application-test.properties.

Spring Boot will load the properties based on the active profile.

5. Custom Properties

Spring Boot also allows you to define your own custom properties, which can be accessed through the @Value annotation or configuration classes.

Example: Defining Custom Properties

You can then inject these properties into your Spring Beans using the @Value annotation:

Alternatively, you can use @ConfigurationProperties for more complex property bindings:

6. Externalizing Configuration

You can externalize your configuration to make your Spring Boot application more flexible. This is especially useful for cloud environments or when you need to change configurations without rebuilding the application.

Spring Boot allows you to load external properties files using the spring.config.location property.

Example: External Configuration

This will load configuration files from the specified directory, allowing you to separate environment-specific settings from the main application package.

Organizing Configuration with application.yml

While application.properties is the default configuration file format, Spring Boot also supports YAML files (application.yml). YAML allows for a more structured and hierarchical configuration format, which can be more readable for complex configurations.

Example of application.yml:

This configuration in application.yml is equivalent to the application.properties example we discussed earlier but provides a more readable and nested structure.

Managing Multiple Profiles with application.properties and application.yml

In a multi-environment application, you might have different configurations for dev, test, and prod environments. You can achieve this in Spring Boot by creating profile-specific property files or YAML configurations.

Example: Multiple Profile Configurations

1. application.properties

2. application-dev.properties

3. application-prod.properties

Spring Boot will load the appropriate properties based on the active profile.

Conclusion

Customizing the application.properties file in Spring Boot is a powerful way to manage your application’s configuration. By using this file, you can adjust key settings such as server port, database connections, logging, and even manage environment-specific configurations through Spring profiles. Additionally, the ability to define custom properties, externalize configuration, and choose between application.properties and application.yml gives you great flexibility and control over your application’s behavior. Whether you’re building a simple application or a complex, multi-environment solution, Spring Boot’s configuration system allows for smooth customization and maintenance.