<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.4.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
    ....
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>
    ....
</dependencies>

spring:
  datasource:
    url: jdbc:h2:mem:my_db;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
    platform: h2
    username: sa
    password:
    driverClassName: org.h2.Driver
  jpa:
    database-platform: org.hibernate.dialect.H2Dialect
    hibernate:
      ddl-auto: create-drop
    properties:
      hibernate:
        show_sql: true
        use_sql_comments: true
        format_sql: true
  h2:
    console:
      enabled: true
      path: /console
      settings:
        trace: false
        web-allow-others: false

@Data
@Entity
@Table(
    name = "class_room"
)
@NoArgsConstructor
public class Classroom
{

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue
    private Long id;

    @Column(nullable = false)
    @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
    private ZonedDateTime dateCreated = ZonedDateTime.now();

    @Column(nullable = false)
    @NotNull(message = "Classroom Name can not be null!")
    private String classroomName;

    ....

}

mvn clean install spring-boot:run

insert into class_room (id, date_created, ... ) values (1, '2018-03-15 18:47:52.69', ... )

insert into class_room (id, date_created, ... ) values (1, now(), ... )