Validating Post Json Data Spring Boot - json

Question

Controller
#RequestMapping(value="/create", method=RequestMethod.POST, consumes={"application/json"})
public Alien addDetails(#RequestBody Alien alien){
return repo.save(alien);
}
Alien.java
#Entity
public class Alien{
#Id
private int id;
private String name;
private String planet;
Getter and setter
Now I want to validate the post json data before saving it to the database.
If any of the field is empty then the controller should return an error.
For example
{"id": 1, "name": "Alien1", "planet":"Mars" }
This is acceptable json data
But if there is any field is missing such as
{"name": "Alien1", "planet":"Mars" }
Then the controller should return an error and not creating the instance of Alien
I tried with #Valid #NotNull still the controller creates an empty instance of Alien and save to the database.

Answer 1

First of all, you should add spring boot validation dependency into your pom.xml :
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
And then add annotations like #NotBlank or #NotEmpty to verify if a value is assigned to that field or not. Those annotations should be on the top of your entity's attributes which you want to validate them.For example:
public class Alien{
#NotBlank(message="Name is mandatory")
private String name;
}
Finally, add #Valid annotation into your controller method like:
public Alien addDetails(#Valid #RequestBody Alien alien){
return repo.save(alien);
}

Answer 2

You should add #Validated annotation to your controller to make #Valid annotation do the work. You should also annotate fields in your Entity with constraints.
I.e., name could be #NotBlank.
And yes, make sure that you have imported:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-validation</artifactId>
</dependency>
Edit:
In Controller, you should not accept Entity as a body. Instead, you should create a DTO object and then map it to the Entity in the service. You should also put validation constraints on the DTO!