Spring Boot Configuration – Properties not loaded

I had recently a very interesting problem using Spring Boot and the automagic concerning the configuration.

The Problem

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'demo.MyApplicationTests': Injection of autowired dependencies failed; 
	nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private java.lang.String demo.MyApplicationTests.url; 
	nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'my.url' in string value "${my.url}" at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
		~[spring-beans-4.1.7.RELEASE.jar:4.1.7.RELEASE] 
	Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'my.url' in string value "${my.url}" at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174) 
		~[spring-core-4.1.7.RELEASE.jar:4.1.7.RELEASE]

Configuration was not available in my Unit tests but it was working fine in the normal application. I spend a lot of time searching but without real good post concerning this issue.

This code already wasn’t working:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = MyWebappApplication.class)
@WebAppConfiguration
public class MyApplicationTests {
    @Value("${my.url}")
    String url;

    @Test
    public void test() {
        System.out.println(url);
    }
}

Even if my application.yml / application.properties was looking good:

my:
   url: any kind of String we inject

The solution

Now here the working sample, do you see the difference?

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = MyWebappApplication.class)
@WebAppConfiguration
public class MyApplicationTests {
    @Value("${my.url}")
    String url;

    @Test
    public void test() {
        System.out.println(url);
    }
}

Yes it is just the @SpringApplicationConfiguration instead of the @ContextConfiguration annotation. (Even if the first is itself just a meta-annotation of the second.) If you look into this new annotation you will find that it uses a different loader class, which makes the difference.

@ContextConfiguration(loader = SpringApplicationContextLoader.class)
@Documented
@Inherited
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface SpringApplicationConfiguration

That’s the trick. Having it in place the Spring Application configuration is successfully parsed an available in your unit test. Doesn’t matter if YAML or just property file.