No #NotBlank validator for type String - spring-boot

Question

I keep getting validator error for quite simple configuration class
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;
import javax.validation.constraints.NotBlank;
#Component
#Data
#Validated
#ConfigurationProperties(prefix = "test")
public class TestProperties {
#NotBlank
String uri;
}
Error is self explaining:
javax.validation.UnexpectedTypeException: HV000030: No validator could be found for constraint 'javax.validation.constraints.NotBlank' validating type 'java.lang.String'. Check configuration for 'uri'
But according to spring boot documentation this should work.

Answer 1

I had the same issue and solved it.
As Yogi stated in his answer, there are two implementations:
import javax.validation.constraints.NotBlank;
and
import org.hibernate.validator.constraints.NotBlank;
Switching from the javax implementation to the hibernate one solved the issue.
Since I didn't use Spring boot, I had to add to my pom.xml:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.2.4.Final</version>
</dependency>

Answer 2

According to Spring-Boot documentation and maven central repo the:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
has the validator included. If you have not spring-boot-starter-web included to your dependencies you can just add the validator:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>

Answer 3

I saw a similar question outside this forum and discovered that the error comes up whenever you try to put #NotBlank annotation on any non-string type field. In my case, the javax.validation.UnexpectedTypeException came up when I annotated a field of type Byte with #NotBlank. So I imported javax.validation.constraints.NotNull, changed the annotation on the Byte field to #NotNull and the error disappeared.
I previously tried replacing import javax.validation.constraints.NotBlank; with import org.hibernate.validator.constraints.NotBlank; to kill the error, but I got a deprecation warning. Programmers are discouraged from using deprecated program elements, so I advise that you use #NotNull annotation instead.
To understand the differences between #NotBlank and #NotNull, see this StackOverflow thread. That way, you get to decide if #NotNull fits your use case.

Answer 4

In my case, it worked okay when running as a standalone application, but gave this same error when running as a WAR; in order to make it work, it was necessary to explicitly import the hibernate-validator as a dependency in order to make it work when running as a WAR:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>7.0.2.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
</dependency>

Answer 5

You can use below options,which works with Spring JPA:
org.hibernate.validator.constraints.NotBlank
javax.validation.constraints.NotNull

Answer 6

I have always used #NotNull.
I think the corresponding POM code is
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>