JSON schema validation while executing POST request and reading POST data entered by user using spring boot rest api

How to validate a JSON input by user during a POST request using a specified schema (we have to validate the JSON data each time it is received through the POST request)?

Add the annotation @Valid(from javax.validation.valid), like so:

public Animal createConfig(@Valid @RequestBody Animal ani) {

On your Animal DTO, add annotations on the field(s) that you want to be validated, example:

public class Animal implements Serializable {
    ...

    @Size(max = 10)
    @NotBlank
    private String name;

    ... 
}

When Spring Boot finds an argument annotated with @Valid, it bootstraps Hibernate Validator(JSR 380 implementation) and ask it to perform bean validation.

When the validation fails, Spring Boot throws a MethodArgumentNotValidException.

Also, how to actually extract data entered by the user form a post request?

Use the getter method on your Animal POJO. Example:

String name = ani.getName();

UPDATE:

Also, if I have a json like: {"hype": {"key1":"value1"} }… then how can I access value1 in hype.key1?

@RestController
public class Main {
    @PostMapping("/all-configs")
    public void createConfig(@Valid @RequestBody Animal ani) {
        Map<String, String> hype = ani.getHype();
        System.out.println(hype.get("key1"));
    }
}

public class Animal implements Serializable {
    private Map<String, String> hype;

    public Map<String, String> getHype() {
        return hype;
    }

    public void setHype(Map<String, String> hype) {
        this.hype = hype;
    }
}

Output:

value1