Enforce not-null field in JSON object

Question

Our REST API receives some JSON objects input where some fields are required to be not null. Those can be either String/Integer or even might be some other class instance as

Answer 1

You can enforce not null validation using a combination of the Jackson JSON library and the javax.validation together with the Hibernate validator package.

If you are using Maven these are the dependencies you can use:

    
        com.fasterxml.jackson.core
        jackson-core
        ${jackson-version}
    
    
        com.fasterxml.jackson.core
        jackson-annotations
        ${jackson-version}
    
    
        com.fasterxml.jackson.core
        jackson-databind
        ${jackson-version}
    
    
    
        javax.validation
        validation-api
        2.0.1.Final
    

    
        org.hibernate.validator
        hibernate-validator
        ${hibernate-validator.version}
    
    
        org.hibernate.validator
        hibernate-validator-annotation-processor
        ${hibernate-validator.version}
    

    
        javax.el
        javax.el-api
        3.0.0
    

    
        org.glassfish.web
        javax.el
        2.2.6
    

Then your code will have to convert some JSON into your annotated object and you will need to validate the object using javax.validation.Validator. Here is some sample code demonstrating how this can be done (see the relevant validate method):

public class ShareLocationService {

    private ObjectMapper mapper = new ObjectMapper();

    private ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

    // Materialize the Java object which contains the validation annotations
    public ShareLocation readFrom(String json) throws IOException {
        return mapper.readerFor(ShareLocation.class).readValue(json);
    }

    // validate and collect the set of validations
    public Set validate(String json) throws IOException {
        ShareLocation shareMyLocation = readFrom(json);
        Validator validator = factory.getValidator();
        Set> violations = validator.validate(shareMyLocation);
        return violations.stream().map(Object::toString).collect(Collectors.toSet());
    }
}

Here is a sample class using the validation annotations:

public class ShareLocation {
    @JsonProperty("Source")
    @NotNull
    private String source;
    @JsonProperty("CompanyCode")
    private String companyCode;
    @JsonProperty("FirstName")
    private String firstName;
    @JsonProperty("LastName")
    private String lastName;
    @JsonProperty("Email")
    private String email;
    @JsonProperty("MobileNumber")
    private String mobileNumber;
    @JsonProperty("Latitude")
    @NotNull
    private Double latitude;
    @JsonProperty("Longitude")
    @NotNull
    private Double longitude;
    @JsonProperty("LocationDateTime")
    @NotNull
    private String locationDateTime;