How to do simple property validation when using Spring @Value

Here's my solution, just put this class in your code (just fix the "my.package" line):

/**
 * Validates the environment-dependent properties during application start. Finds all spring beans, which classes are in
 * defined package, validates them and in case of error tries to log the property name (not class field name), taken
 * from {@link Value} annotation.
 * 
 * @author Tomasz
 */
@Component
public class ConfigurationChecker implements ApplicationListener<ContextRefreshedEvent> {
    private static final Logger LOG = LoggerFactory.getLogger(ConfigurationChecker.class);

    // this is a property, that is set in XML, so we bind it here to be found by checker. For properties wired directly in Beans using @Value just add validation constraints
    @Value("${authorization.ldap.url}")
    @NotBlank
    private String ldapUrl;

    private static final String FAIL_FAST_PROPERTY = "hibernate.validator.fail_fast";
    private Validator validator = Validation.byDefaultProvider().configure().addProperty(FAIL_FAST_PROPERTY, "false")
            .buildValidatorFactory().getValidator();

    /**
     * Performs the validation and writes all errors to the log.
     */
    @SneakyThrows
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {

        LOG.info("Validating properties");

        Set<ConstraintViolation<Object>> allViolations = new HashSet<>();

        // Find all spring managed beans (including ConfigurationChecker)...
        for (String beanName : event.getApplicationContext().getBeanDefinitionNames()) {
            Object bean = event.getApplicationContext().getBean(beanName);

            // ...but validate only ours.
            if (bean.getClass().getCanonicalName().startsWith("my.package")) {
                Set<ConstraintViolation<Object>> viol = this.validator.validate(bean);
                LOG.info("Bean '" + beanName + "': " + (viol.isEmpty() ? " OK" : viol.size() + " errors found"));
                allViolations.addAll(viol);
            } else {
                continue;
            }

        }

        // if any error found...
        if (allViolations.size() > 0) {

            for (ConstraintViolation<Object> violation : allViolations) {
                // ...extract "property.name" from field annotation like @Value("${property.name}")
                String propertyName = violation.getLeafBean().getClass()
                        .getDeclaredField(violation.getPropertyPath().toString()).getAnnotation(Value.class).value();
                propertyName = StringUtils.substring(propertyName, 2, -1);

                // .. log it ..
                LOG.error(propertyName + " " + violation.getMessage());
            }

            // ... and do not let the app start up.
            throw new IllegalArgumentException("Invalid configuration detected. Please check the log for details.");
        }
    }
}

      

        
        
        
      

    

And here's a test for it:

@RunWith(EasyMockRunner.class)
public class ConfigurationCheckerTest extends EasyMockSupport {

    @TestSubject
    private ConfigurationChecker checker = new ConfigurationChecker();

    @Mock
    private ContextRefreshedEvent event;
    @Mock
    private ApplicationContext applicationContext;

    @Test(expected = IllegalArgumentException.class)
    public void test() {

        expect(this.event.getApplicationContext()).andReturn(this.applicationContext).anyTimes();
        expect(this.applicationContext.getBeanDefinitionNames()).andReturn(new String[] { "configurationChecker" });
        expect(this.applicationContext.getBean("configurationChecker")).andReturn(this.checker);

        replayAll();
        this.checker.onApplicationEvent(this.event);

        verifyAll();
    }

}