Validation is not working Spring 2.3.3.RELEASE

Question

Someone please help i am new to spring boot. I am trying to do form validation in spring boot version 2.3.3 RELEASE. When I use any constraints from import javax.validation.constraints.* it says error.

I found the solution like to add the below dependency, but when i add this dependency it's also throwing error.

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

Error is

Failed to read artifact descriptor for org.springframework.boot:spring-boot-starter-validation:jar:2.3.3.RELEASE

Answer 1

I used a simple example from Baeldung to test the behavior. For the initialization of the project I used the Spring Initializr. Additionally I used Lombok to make the code clearer. The following part shows the code snippets:

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.3.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>11</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>

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

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

User:

package com.example.demo;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotBlank;

import lombok.Data;

@Entity
@Data
public class User {

    @Id
    @GeneratedValue
    private long id;

    @NotBlank(message = "Name is mandatory")
    private String name;

    @Min(18)
    private int age;
}

UserRepository:

package com.example.demo;

import org.springframework.data.repository.CrudRepository;

public interface UserRepository extends CrudRepository<User, Long> {

}

UserController:

package com.example.demo;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import lombok.extern.slf4j.Slf4j;

@RestController
@Slf4j
public class UserController {

    @Autowired
    private UserRepository userRepository;

    @PostMapping("/users")
    public ResponseEntity<Void> addUser(@Valid @RequestBody User user) {
        log.info("save new user {}", user);

        userRepository.save(user);
        return ResponseEntity.noContent().build();
    }
}

When you start the server, you can create a post request to create a user. And depending if the sent user is valid you will get a NoContent or a BadRequest.

{
    "name": "test1",
    "age": 20
}

If it doesn't work or you can't find the problem in your code, you can post your code and we can test it ourselves. Maybe you forgot a no args constructor or the getter/setter methods in your entity or something else.

EDIT:

I have looked at the debug message and maybe this article will help you. The problem can be solved by deleting the .m2 folder to re-download all dependencies.