Bdtjtk

I am trying to use Jackson library for deserialization since I have a scenario wherein I have to validate for null values in many JsonProperty if it is set as required=true.

Here is the code snippet.

public class JacksonValidator {

    private static final ObjectMapper MAPPER = new ObjectMapper();



    public static void main(String args) {



        // Should succeed since all properties have value and required=true holds good

        validate("{"id": "1","age": 26,"name": "name1"}");



        // Should throw exception since name is null (because of required=true)

        validate("{"id": "2","age": 28,"name": null}");



        // Should throw exception since id is null (because of required=true)

        validate("{"id": null,"age": 27,"name": "name2"}");

    }



    public static void validate(String json) {



        try {

            Customer customer = MAPPER.readValue(json, Customer.class);

            System.out.println(customer);

        }

        catch (IOException e) {

            throw new DeserializationException(String.format("Validation failed. Unable to parse json %s", json), e);

        }

    }



    @Setter

    @Getter

    @ToString

    public static class Customer {

        private String id;

        private Integer age;

        private String name;



        @JsonCreator

        public Customer(@JsonProperty(value = "id", required = true) String id,

                @JsonProperty(value = "age", required = false) Integer age,

                @JsonProperty(value = "name", required = true) String name) {

            this.id = id;

            this.age = age;

            this.name = name;

        }

    }

}

As you can see in the above code, I am trying to deserialize JSON into Customer class. If the required property is set to true for a JsonProperty and while deserialization if this property encounters null(for id and name field in the above code), I have to throw a custom DeserializationException.

And also I need to have null values processed(shouldn't fail) for fields where required=false is set in JsonProperty(for age field).

Here I cannot use MAPPER.setSerializationInclusion(JsonInclude.Include.NON_NULL) since I need to process null values for required=false fields.

Please let me know how this could be achieved using ObjectMapper.readValue method or any other method that holds good here.

Any suggestions would be appreciated.

You can't use @JsonProperty for null validation. It only checks whether value is present or not. From javadocs

Property that indicates whether a value (which may be explicit null) is expected for property during deserialization or not.

For null validation you can use Bean validation JSR-380. Hibernate example:

Maven dependencies:

<!-- Java bean validation API - Spec -->

<dependency>

    <groupId>javax.validation</groupId>

    <artifactId>validation-api</artifactId>

    <version>2.0.1.Final</version>

</dependency>



<!-- Hibernate validator - Bean validation API Implementation -->

<dependency>

    <groupId>org.hibernate</groupId>

    <artifactId>hibernate-validator</artifactId>

    <version>6.0.11.Final</version>

</dependency>



<!-- Verify validation annotations usage at compile time -->

<dependency>

    <groupId>org.hibernate</groupId>

    <artifactId>hibernate-validator-annotation-processor</artifactId>

    <version>6.0.11.Final</version>

</dependency>



<!-- Unified Expression Language - Spec -->

<dependency>

    <groupId>javax.el</groupId>

    <artifactId>javax.el-api</artifactId>

    <version>3.0.1-b06</version>

</dependency>



<!-- Unified Expression Language - Implementation -->

<dependency>

    <groupId>org.glassfish.web</groupId>

    <artifactId>javax.el</artifactId>

    <version>2.2.6</version>

</dependency>

Then you can use it like:

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

Validator validator = factory.getValidator();

Set<ConstraintViolation<Customer>> constraintViolations = validator.validate(customer);

if (constraintViolations.size() > 0) {

    throw new DeserializationException(String.format("Validation failed. Unable to parse json %s", json), e);

}