Property File Selection in Spring Boot

Property File Selection in Spring Boot | Generated by AI

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In a Spring Boot Maven project, you have two properties files, appProperties.properties and appProperties-hk.properties, located under src/main/resources. To control which properties file is used, particularly to specify the use of the -hk properties, you can leverage Spring Boot’s configuration mechanisms. Here’s how you can do it:

Solution

Create an application.properties File
- By default, Spring Boot looks for application.properties or application.yml in src/main/resources to load configuration settings.
- To use your custom properties files (appProperties.properties and appProperties-hk.properties), you need to inform Spring Boot to look for files with the base name appProperties instead of the default application.
- Add the following line to a new application.properties file in src/main/resources:
```
spring.config.name=appProperties
```
- This setting tells Spring Boot to load appProperties.properties as the base configuration file, and it will also automatically look for profile-specific variants like appProperties-{profile}.properties when a profile is active.
Use Spring Profiles to Specify the -hk Properties
- Spring Boot supports profiles, which allow you to load additional or overriding properties files based on the active profile.
- Since your file is named appProperties-hk.properties, it follows the pattern appProperties-{profile}.properties. Here, “hk” can be treated as a profile name.
- To use appProperties-hk.properties, activate the “hk” profile when running your application. Spring Boot will then load both appProperties.properties and appProperties-hk.properties, with properties in appProperties-hk.properties overriding any matching properties in appProperties.properties.
How to Activate the “hk” Profile
- Via Command Line: When running your Spring Boot application, specify the active profile using the --spring.profiles.active argument. For example:
```
java -jar target/myapp.jar --spring.profiles.active=hk
```
  Replace myapp.jar with the name of your application’s JAR file generated by Maven.
- Via Maven: If you’re running the application using the spring-boot:run goal, configure the profile in your pom.xml:
```
<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <profiles>
            <profile>hk</profile>
        </profiles>
    </configuration>
</plugin>
```
  Then run:
```
mvn spring-boot:run
```
- Via System Property: Set the profile as a JVM argument:
```
java -Dspring.profiles.active=hk -jar target/myapp.jar
```
- Via Environment Variable: Export the profile in your environment (e.g., in a Unix-like system):
```
export SPRING_PROFILES_ACTIVE=hk
java -jar target/myapp.jar
```

How It Works

With spring.config.name=appProperties set in application.properties, Spring Boot uses appProperties as the base name for configuration files.
When no profile is active, only appProperties.properties is loaded.
When the “hk” profile is activated (e.g., via --spring.profiles.active=hk), Spring Boot loads both appProperties.properties and appProperties-hk.properties. Properties defined in appProperties-hk.properties take precedence over those in appProperties.properties if there are any duplicates.

Final Steps

Ensure both appProperties.properties and appProperties-hk.properties are in src/main/resources.
Add application.properties with spring.config.name=appProperties to src/main/resources.
Run your application with the “hk” profile activated to use the -hk properties.

This approach aligns with Spring Boot conventions, making it a typical and straightforward way to control which properties file is used in your project. To specifically use the -hk properties, simply activate the “hk” profile as described above.

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