How do I use a variable from an application.yml file in my normal code?

Question

For example, let's say that in my yml file I had a variable called indicator. And based on what the indicator variable's value was I want the code to do something different. How would I access the yml variable in the regular code and use it accordingly?

Solution 1

You can use this:

@Value("${your.path.yml.string}")
private String x;

YML:

your:
  path:
    yml:
      string: hello

x will be "hello"

Solution 2

1. You need to use Spring Expression Language which says we should write it as

    @Value("${spring.application.name}") 
    private String appName;

2. For Default value if key is not present in yaml/yml or properties file

    @Value("${spring.application.name: defaultValue}") 
    private String appName;

3. The last way you can fetch value is using environment object

    @Autowired  
    private Environment environment;
       
    String appName = environment.get("spring.application.name");

Solution 3

You can add @Value annotation to any field in your beans.

@Value("$(path.to.your.variable)")
String myString;

Works with constructors as well.

public MyClass(@Value("$(path.to.your.variable)") String myString) {

Solution 4

You can use @Value on fields or parameters to assign the property to some variable.

Property example:

@Value("${indicator}")
private String indicator

Parameter example:

private void someMethod(@Value("${indicator}") String indicator) {
    ...
}

Then you can use indicator as you want.

Note: the class where you use @Value should be a Spring Component

View more solutions

Comments

[Arjun Kalidas]

Refer this link: baeldung.com/spring-yaml this helped me understand this better.

[chrylis -cautiouslyoptimistic-]

This entire functionality is one of the core things Spring provides in the first place.

[Rishabh Sharma]

It is not mentioned anywhere in the question that spring is required (inspite of the tag). I guess - "To a man with a hammer, everything looks like a nail" :)

[nolanite1]

what would the path be like? just the path to the yaml file where the variable is?

[chrylis -cautiouslyoptimistic-]

It's tagged spring-boot and he mentions application.yml by name.

[nolanite1]

oh ok. when i tried that i got an error saying Unsatisfied dependency expressed through field 'sampleService'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sampleServiceImpl': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'indicator.operation' in value "${indicator.string}

[luisfa19]

use @Component in the class.

[nolanite1]

wait the class i'm using it in or do i have to create a class for the variable?

[luisfa19]

could be in the class you are using it