@notblank not working in spring boot

To use the @NotBlank annotation in Spring Boot, you need to follow these steps:

Add Dependency: First, make sure you have the necessary dependencies in your project. The @NotBlank annotation is part of the Hibernate Validator library, so you need to include it in your project's dependencies. You can add the following dependency to your pom.xml file if you are using Maven:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

If you are using Gradle, you can add the following dependency to your build.gradle file:

implementation 'org.springframework.boot:spring-boot-starter-validation'

Enable Validation: In your Spring Boot application, you need to enable validation by adding the @EnableWebMvc annotation to one of your configuration classes. This annotation enables Spring's validation support:

@Configuration
@EnableWebMvc
public class WebConfig {
    // Configuration code
}

Use @NotBlank: Now you can use the @NotBlank annotation to validate the input of your fields or method parameters. The @NotBlank annotation ensures that the annotated element must not be null and must have at least one non-whitespace character. Here's an example:

public class User {
    @NotBlank
    private String username;

    // Getters and setters
}

In the above example, the username field of the User class will be validated to ensure that it is not blank.

Handle Validation Errors: If a validation error occurs, you can handle it in various ways. One common approach is to use Spring's BindingResult interface. Here's an example of handling validation errors in a Spring MVC controller:

@PostMapping("/users")
public String createUser(@Valid @RequestBody User user, BindingResult result) {
    if (result.hasErrors()) {
        // Handle validation errors
    }
    // Process the user
    return "success";
}

In the above example, the @Valid annotation triggers the validation of the User object passed in the request body. The validation errors are then stored in the BindingResult object, which you can use to handle the errors appropriately.

That's it! You have now enabled and used the @NotBlank annotation in Spring Boot for input validation. Remember to handle the validation errors properly in your application.