How to exclude validation on specific fields in Spring Java

Question

I've to ignore the validation if value is not set on specific fields. For instance, I've name, productId, productSerial, productDesc and productPrice

In this, name is mandatory field so always validation happens, rest of the fields are optional but if value is set in these fields I've to validate. So I wrote custom validator for these optional fields and for name I'm using javax.validation.constraints.NotNull like this @NotNull(message = "Name cannot be null")

I get all these value in Map from upstream app and set these value in my Java bean and perform the validation.

If all the fields are available in Map, validation is working without any issue but if user set only name which is mandatory and leave the optional field - my custom validator trying to validate and throwing NullPointerException which I don't want.

I want my custom validator to validate if values are set on these optional fields else ignore the validation - I don't know how to achieve this :( It would be really appreciated if someone can help me with this and provide some sample example.

Working scenario:

Map<String,String> map = new HashMap();
map.put("name", "Apple"); // Always user will set this value - Mandatory

map.put("productId", "2342342"); // Optional but need to validate if this value is set
map.put("productSerial", "4334DDF43"); // Optional but need to validate if this value is set
map.put("productDesc", "iPhone"); // Optional but need to validate if this value is set
map.put("productPrice", "1303"); // Optional but need to validate if this value is set

// Once I get the map from upstream, I've to set the map value in my bean and validate 
Product product = new Product();
product.setName(map.get("name"));
product.setProductId(map.get("productId"));
product.setProductSerial(map.get("productSerial"));
product.setProductDesc(map.get("productDesc"));
product.setProductPrice(map.get("productPrice"));

Getting NullPointerException when below scenario occurs

Map<String,String> map = new HashMap();
map.put("name", "Apple"); 

Product product = new Product();
product.setName(map.get("name"));
product.setProductId(map.get("productId"));
product.setProductSerial(map.get("productSerial"));
product.setProductDesc(map.get("productDesc"));
product.setProductPrice(map.get("productPrice"));

Please find my code below:

Product.java

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

import javax.validation.constraints.NotNull;

@Getter
@Setter
@ToString
@ValidParam
public class Product {

    @NotNull(message = "Name cannot be null")
    private String name;

    private String productId;
    private String productSerial;
    private String productDesc;
    private String productPrice;
}

ValidParam.java

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;

@Documented
@Constraint(validatedBy = ProductValidator.class)
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ValidParam {
    String message() default "Invalid product data.";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

ProductValidator.java

import org.springframework.beans.BeanWrapperImpl;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;



public class ProductValidator implements ConstraintValidator<ValidParam, Object> {

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {

        String productId = (String) new BeanWrapperImpl(value).getPropertyValue("productId");
        String productSerial = (String) new BeanWrapperImpl(value).getPropertyValue("productSerial");


        String productDesc = (String) new BeanWrapperImpl(value).getPropertyValue("productDesc");
        String productPrice = (String) new BeanWrapperImpl(value).getPropertyValue("productPrice");



        if ((productId != null || productSerial != null) || (productDesc != null && productPrice != null)) {
            System.out.println("validation success");
            return true;
        } else {
            System.out.println("validation failed");
            return false;
        }

    }
}

Main.java

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class Main {
    public static void main(String[] args) {
        // I get this Map from the upstream app
        Map<String,String> map = new HashMap();
        map.put("name", "Apple"); // Always user will set this value - Mandatory
        map.put("productId", "2342342"); // Optional but need to validate if this value is set
        map.put("productSerial", "4334DDF43"); // Optional but need to validate if this value is set
        map.put("productDesc", "iPhone"); // Optional but need to validate if this value is set
        map.put("productPrice", "1303"); // Optional but need to validate if this value is set
       
 // Once I get the map from upstream, I've to set the map value in my bean and validate 
            Product product = new Product();
            product.setName(map.get("name"));
            product.setProductId(map.get("productId"));
            product.setProductSerial(map.get("productSerial"));
            product.setProductDesc(map.get("productDesc"));
            product.setProductPrice(map.get("productPrice"));
            ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
            Validator validator = factory.getValidator();
            Set<ConstraintViolation<Product>> violations = validator.validate(product);
            for (ConstraintViolation<Product> violation : violations) {
                System.out.println(violation.getMessage());
                throw new NullPointerException(violation.getMessage());
            }
        }
    }