问如何在spring boot中使用@NotNull？

EN

<dependency>
    <groupId>org.hibernate.validator</groupId>
    <artifactId>hibernate-validator</artifactId>
</dependency>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.4.RELEASE</version>
</parent>

import javax.validation.constraints.NotNull;
//other imports ommited

@Component
@ConfigurationProperties(prefix = "collector")
public class CollectorProperties {

    @NotNull
    private String urlCDI;

    //getters and setters
}

@SpringBootApplication
@EnableConfigurationProperties
@ComponentScan({ "otherPackages", "packageWhereCollectorPropertiesIs" })

collector.urlCDI=https://www.cetip.com.br/Home

//@Component class variables:
@Autowired
private CollectorProperties props;

   //inside some method
    URL url = new URL(props.getUrlCDI());