AroundAround
Sign in Sign up
Menu

How to populate Spring @Value during Unit Test in Java

Emma Brown
admin
#java #reactjs
Share post:
Share

In this questions talks about How to populate Spring @Value during Unit Test in Java

How can I write a unit test for a Spring bean used for form validation, which includes a @Value property, without relying on a properties file?

The bean is annotated with @Component and has a field initialized like this:
@Value("${this.property.value}") private String thisProperty;

I want to test the validation methods in the class, but I don't want changes in the properties file to affect the test. My focus is on testing the validation logic, not the property value itself.

Is there a way to programmatically set the @Value property within the test class, using only Java code, and then test the bean with that setup? I came across a "How To" guide that seems close but still relies on a properties file. I'd prefer a solution that avoids using any external configuration.

Solution in a Nutshell

Solution

To unit test a Spring @Component that uses the @Value annotation without relying on external property files, you can consider the following approaches:

Use ReflectionTestUtils to Set the Field Directly: Spring's ReflectionTestUtils provides a setField method that allows you to set the value of private fields directly. This approach enables you to instantiate the component in your test and manually inject the desired value without involving the Spring context.

Stack Overflow

 

Leverage the @TestPropertySource Annotation: Starting from Spring 4.1, you can use the @TestPropertySource annotation to define in-line properties directly within your test class. This method allows you to specify property values that will be injected into your component during testing, eliminating the need for external property files.

Stack Overflow

 

Implement Constructor Injection: Refactor your component to use constructor injection for the properties. By moving the @Value annotation to the constructor parameters, you can instantiate the component with the desired values directly in your test, simplifying the injection process and avoiding the need for reflection or Spring context initialization.

Stack Overflow

 

Each of these methods allows you to control the injected values during testing without depending on external property files, ensuring that your tests remain stable and focused on the validation logic of your component.