How to use environment variables in springboot

spring.config.import=optional:.env[.properties]

with the above code in application file(application.properties / yml), you can use the environment variable in your project

1. in application file
in application file, you can just use ${variable_name} to use the variable.

2. in code
in code(java files), you can use annotation @Value("{variable_name}") to use the variable.

3. ConfigurationProperties
if env variables are grouped with prefix (like apple.name and apple.count), you can easily map them through Configuration Properties. 
For example, instead of writing @Value("{apple.name}") and @Value("{apple.count}") respectively, you can just write

@ConfigurationProperties(prefix = "apple")
public class AppleProperties {
    private string name;
    private int count;
}

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Leetcode

이미지
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