application.yml vs application.properties in Spring Boot

Introduction to Configuration in Spring Boot

Spring Boot provides flexible and convenient ways to configure your application properties. Two common formats for configuration files are application.yml and application.properties. Both formats allow you to externalize configuration settings from your code, making it easier to manage and modify various aspects of your application.

In this guide, we’ll explore the differences between application.yml and application.properties in Spring Boot and provide insights into when to use each format.

Prerequisites

Before we delve into the comparison, make sure you have a basic understanding of Spring Boot and its configuration principles.

Using application.properties

application.properties is a widely used configuration format in Spring Boot. It uses a key-value pair structure and is based on the .properties file format. Each line represents a property, and properties are organized hierarchically using dots.

Here’s an example of using application.properties to configure a database connection:

# Database Configuration
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=myuser
spring.datasource.password=mypassword

In this example, properties like spring.datasource.url, spring.datasource.username, and spring.datasource.password are configured.

Using application.yml

application.yml is an alternative configuration format that uses YAML (YAML Ain’t Markup Language). YAML is known for its clean and human-readable syntax, making complex configurations more intuitive.

Here’s the equivalent configuration using application.yml:

# Database Configuration
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: myuser
    password: mypassword

In this YAML example, the same database configuration is organized in a nested structure.

Advantages of application.yml

1. Readability: YAML’s indentation-based structure enhances readability, especially for nested configurations, making it more human-friendly than .properties files.
2. Hierarchical Organization: YAML allows you to represent hierarchical data using indentation, which can result in a more organized configuration.
3. Collections and Lists: YAML natively supports collections and lists, simplifying the configuration of arrays or multiple values.
4. Multiline Strings: YAML makes it easy to represent multiline strings, which can be helpful for long configuration values.

Advantages of application.properties

1. Simplicity: The key-value pair structure of .properties files is simple and straightforward, making it easy to understand and use.
2. Widespread Usage: .properties files have been widely used in Java applications for configuration, making them familiar to many developers.
3. Java Properties Compatibility: If you’re dealing with existing Java Properties files, using .properties format might be more suitable.

Choosing Between Formats

The choice between application.yml and application.properties largely depends on your team’s preferences and the complexity of your configuration. Here are some considerations to help you decide:

• Use application.yml When: You prefer a more human-readable and structured format, your configuration is complex and hierarchical, or you need to work with collections and lists.
• Use application.properties When: You value simplicity and are comfortable with the key-value pair syntax, or your existing project uses Java Properties files.

Combining application.yml and application.properties

In Spring Boot, you can use both application.yml and application.properties files simultaneously. This can be useful when you want to take advantage of the strengths of both formats for different parts of your configuration.

Let’s illustrate this with an example. Suppose you have a complex configuration involving both database settings and custom properties. You might choose to use application.yml for the database configuration and application.properties for custom properties:

application.yml:

# Database Configuration
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: myuser
    password: mypassword

application.properties:

# Custom Properties
custom.property1=value1
custom.property2=value2

In this scenario, you’ve leveraged the structured nature of YAML for the database configuration and the simplicity of .properties for custom properties.

Profile-Specific Configuration

Both application.yml and application.properties support profile-specific configuration. Profiles allow you to define different configurations for different environments or use cases.

For instance, you can have separate profiles for development, testing, and production environments. Each profile can have its own set of configuration properties.

# Development Profile Configuration
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/devdb
    username: devuser
    password: devpassword

# Production Profile Configuration
spring.datasource.url=jdbc:mysql://prod-server:3306/proddb
spring.datasource.username=produser
spring.datasource.password=prodpassword

By using profiles, you can maintain specific configurations for each environment while keeping your application code consistent.

Spring Boot Configuration Hierarchy

When using both application.yml and application.properties, keep in mind that application.properties takes precedence over application.yml. In other words, if a property is defined in both files, the value from application.properties will be used.

Conclusion

The choice between application.yml and application.properties depends on your preferences and the complexity of your configuration. However, it’s worth noting that Spring Boot encourages the use of application.yml due to its readability and hierarchical structure. By combining both formats and utilizing profile-specific configuration, you can effectively manage your application’s properties for different environments or use cases. The key is to ensure that your configuration remains clear, organized, and easily maintainable throughout the development lifecycle.