pom.xml 파일에 아래 디펜더시 2개 추가해주면 됩니다. javax.validation만 추가하면 작동 안합니다. <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-validation --><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-validation</artifactId> <version>2.5.0</version></dependency><!-- https://mvnrepository.com/artifact/javax.validation/validation-api --><dependency> <groupId>javax.validation</groupId> <artifactId>validation-api</artifactId> <version>2.0.1.Final</version></dependency>