Framework Error

What This Error Means

This error occurs when Spring Boot's auto-configuration feature is not properly enabled in the application, typically due to a missing or incorrectly configured configuration class.

Why It Happens

This error happens because Spring Boot's auto-configuration relies on the presence of a configuration class annotated with @EnableAutoConfiguration. If this class is missing or incorrectly configured, the @Valid annotation used for bean validation will not be properly injected into the entity, resulting in this error.

How to Fix It

1. 1To fix this error, add a configuration class annotated with @EnableAutoConfiguration to your application. For example, if you're using the Spring Boot Starter Web module, you can add the following configuration class:
2. 2// Before (broken code)
3. 3// After (fixed code)
4. 4@SpringBootApplication
5. 5class MyApplication {
6. 6 public static void main(String[] args) {
7. 7 SpringApplication.run(MyApplication.class, args);
8. 8 }
9. 9}
10. 10// Then, add the @Valid annotation to your entity class as follows:
11. 11@Entity
12. 12public class User {
13. 13 @Id
14. 14 @GeneratedValue(strategy = GenerationType.IDENTITY)
15. 15 private Long id;
16. 16 @Size(min = 5, max = 50)
17. 17 @Column(name = 'username', unique = true)
18. 18 private String username;
19. 19 @Valid
20. 20 private Address address;
21. 21}
22. 22class Address {
23. 23 private String street;
24. 24 private String city;
25. 25}

Example Code Solution

@SpringBootApplication
class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Size(min = 5, max = 50)
    @Column(name = 'username', unique = true)
    private String username;

    @Valid
    private Address address;
}

class Address {
    private String street;
    private String city;
}

@SpringBootApplication
class MyApplication {
    @EnableAutoConfiguration
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Size(min = 5, max = 50)
    @Column(name = 'username', unique = true)
    private String username;

    @Valid
    private Address address;
}

class Address {
    private String street;
    private String city;
}