CODEWITHSUNDEEP
javavalidationspring-bootcollectionsjava-8
Aditya Narayan Dixit
Aditya Narayan Dixit

Reputation: 2119

Validating member List variables for null values

The structure that I have is something like below:

Class A{
    String str;
    int i;
    List<B> bs;
    C c;
    @NotNull
    List<D> ds;
}

Class B{
    @NotNull
    List<E> es;
}

Class C{
    List<String> s;
}

Class E{
    @NotNull
    List<String> s;
}

For the list variables that are annotated with @NotNull I need to throw validation error if any of them variables has one or more null objects. While for the other list variables I just need to remove the nulls; What would be the best way to achieve this?

Upvotes: 1

Views: 1830

Answers (3)

Aditya Narayan Dixit
Aditya Narayan Dixit

Reputation: 2119

This is the final code that I wrote, just a few tweaks to the code that Hadi posted. I hope it helps: Annotation:

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;


@Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = ListValidator.class)
@Documented
public @interface ValidList {
  String message() default "Null values are not allowed in array fields.";

  Class<?>[] groups() default {};

  Class<? extends Payload>[] payload() default {};
}

Validator Class:

import java.util.List;
import java.util.Objects;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class ListValidator implements ConstraintValidator<ValidList, List<? extends Object>> {

  @Override
  public boolean isValid(List<? extends Object> list, ConstraintValidatorContext context) {
    return list.stream().noneMatch(Objects::isNull);
  }

  @Override
  public void initialize(ValidList constraintAnnotation) {}
}

Upvotes: 0

ByeBye
ByeBye

Reputation: 6956

If you are using validation 2.0+ you can put annotation inside: List<@NotNull String> s;

Upvotes: 1

Hadi
Hadi

Reputation: 17299

You should define custom annotation for validating.

so define custom annotation like bellow. 

@Target({ElementType.FIELD, ElementType.PARAMETER,ElementType.ANNOTATION_TYPE})
@Retention(RUNTIME)
@Constraint(validatedBy = ValidateListValidator.class)
@Documented
public @interface ValidateList {
}

and implement ValidateListValidator like this: 

public class ValidateListValidator implements ConstraintValidator<ValidateList, List<Object>> {

private ValidateList validateList;
@Override
public void initialize(ValidateList validateList) {
    this.validateList = validateList;
}

@Override
public boolean isValid( List<Object> list, ConstraintValidatorContext constraintValidatorContext) {
    return list.stream().noneMatch(Objects::isNull);
  }

 }

and for test it 

@Test
public void test() {
    boolean valid = validator.isValid(Arrays.asList("test","this",null),context);
    assertThat(valid, is(false));
}

Upvotes: 1

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