Inject Spring beans as method parameters in JUnit5

SpringMethodParameterResolver.java

import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.ParameterContext;
import org.junit.jupiter.api.extension.ParameterResolutionException;
import org.junit.jupiter.api.extension.ParameterResolver;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.junit.jupiter.SpringExtension;

import java.lang.reflect.Parameter;
import java.util.Optional;

/**
 * Annotation your spring boot test with
 *
 * <code>@ExtendWith(SpringMethodParameterResolver.class)</code>
 *
 * and just define beans in your test methods as parameters.
 *
 * <code>
 *     @BeforeEach
 *     public void setup(EntityManager entityManager, @Qualifier("test") DataSource ds){
 *        // ...
 *     }
 * </code>
 * or
 * <code>
 *     @Test
 *     public void someTest(EntityManager entityManager){
 *        // ...
 *     }
 * </code>
 *
 */
public class SpringMethodParameterResolver implements ParameterResolver {

    @Override
    public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
        try {
            return resolveParameter(parameterContext, extensionContext) != null;
        } catch (NoSuchBeanDefinitionException e) {
            throw new ParameterResolutionException("No bean definition found for parameter " + parameterContext.getParameter(), e);
        }
    }

    @Override
    public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) throws ParameterResolutionException {
        Parameter parameter = parameterContext.getParameter();

        Qualifier qualifier = parameter.getAnnotation(Qualifier.class);
        Optional<String> beanName = Optional.ofNullable(qualifier).map(Qualifier::value);

        Class<?> type = parameter.getType();
        return getBean(extensionContext, type, beanName);
    }

    private Object getBean(ExtensionContext extensionContext, Class<?> type, Optional<String> beanName) {
        ApplicationContext applicationContext = SpringExtension.getApplicationContext(extensionContext);
        Optional<Object> bean = beanName.map(n -> applicationContext.getBean(n, type));
        return bean.orElseGet(() -> applicationContext.getBean(type));
    }
}