Java Object Validation

Developed in order to check if an instance of a class is valid according to the predicates given as annotations on its fields.

The fields to be validated can also be put on a list of criteria, this can be done without the annotations aspect.

It prevents the classic control flow like the if-else blocks.

Validation process can be done using two ways:

1. Using annotations.
2. Using customized criteria.

Use it as a maven dependency :

   <dependency>
            <groupId>io.github.belmomusta</groupId>
            <artifactId>validation</artifactId>
            <version>1.1</version>
   </dependency>

Examples of use :

1. Using annotations

Suppose we have a Person class, and for all the instances, we want that the first name and the last name be assigned and not left null :

class Person {

   @Validation
   private String name;

   @Validation
   private String lastName;
   // .... other fields...
   // .... getters and setters..
   }
   

And we will create an instance, then we check if it is valid or not:

  AnnotationValidator<Person> annotationValidator = new AnnotationValidator<>();
  Person person = new Person();
         person.setName("Mustapha");
         person.setLastName("Belmokhtar");

  boolean isValid = annotationValidator.checkValidation(person);
  ValidationReport validationReportItem = annotationValidator.getValidationReport(person); // gives the details of each field

Result :

 true
{lastName=|found=String:Belmokhtar, expected={!=null}:[], valid=true|, name=|found=String:Mustapha, expected={!=null}:[], valid=true|}

Validation by Operators:

   class Person{
   // ... others fields 
   @Validation(operator = Operator.GREATER_THAN, value = "18")
    private int age;
    // ... getters and setters ...
    }

   Person person = new Person(); 
   person.setAge(20);
   AnnotationValidator<Person> annotationValidator = new AnnotationValidator<>();
   boolean isValid = annotationValidator.check(person);
   ValidationReport validationReportItem = annotationValidator.getValidationReport(person);

Result :

true
{age=|found=Integer:20, expected={>}:[18], valid=true|}

2.Using criteria :

You can also perform validation over objects using Criteria:

     CriteriaValidator<Student> studentCriteriaValidator = new CriteriaValidator<>();

    studentCriteriaValidator
                    .add(Criterion.of("name").is("mustapha"))
                    .add(Criterion.of("address").notNull())
                    .add(Criterion.of("age").greaterOrEquals(4))
                    .add(Criterion.of("phoneNumber").matches("\\d{10}"));

            student.setName("mustapha");
            student.setAddress("wall street");
            student.setAge(4);
            student.setPhoneNumber("1234567890");
            System.out.println(studentCriteriaValidator.getValidationReport(student));
            assertTrue(studentCriteriaValidator.check(student));

Output :

address=|found=String:wall street, expected={!=null}:[null], valid=true|, phoneNumber=|found=String:1234567890, expected={REGEX}:[\d{10}], valid=true|, name=|found=String:mustapha, expected={==}:[mustapha], valid=true|, age=|found=Integer:4, expected={>=}:[4], valid=true|}

Criteria over complex Objects:

To perform validation by criteria over complex objects, you only have to specify the filed path of the wanted field, for example:

  class Student {
   // omittd fields for brievety 
    private Matters matters
    //... getters and setters
    }
    
    //....
      class Matters {
    private double science;
    private double maths;
    private double languages;
    //...
    }
    //... 

Validation process:

   CriteriaValidator<Student> studentCriteriaValidator = new CriteriaValidator<>();
   studentCriteriaValidator.add(Criterion.of("matters.maths").is(20.0));
   Matters matters = new Matters();
   matters.setMaths(19.99);
   student.setMatters(matters);
   System.out.println(studentCriteriaValidator.getValidationReport(student));

Output

{matters.maths=|found=Double:19.99, expected={<}:[20.0], valid=true|}

Validation overs arrays and collections:

    class Book {
    private int[] isbn;
    private TreeSet<String> keywords;

    // .. other fields
    //.. getters and setters
     }

Validation process:

        Book book = new Book();
        CriteriaValidator<Book> bookCriteriaValidator = new CriteriaValidator<>();

       bookCriteriaValidator.add(Criterion.of("keywords").length(3))
                       .add(Criterion.of("isbn").length(11));

               int[] isbn = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
               Set<String> keywords = new TreeSet<>();
               keywords.add("science");
               keywords.add("earth");
               keywords.add("universe");
               book.setKeywords(keywords);
               book.setIsbn(isbn);
               System.out.println(bookCriteriaValidator.getValidationReport(book));
               assertTrue(bookCriteriaValidator.check(book));

Output

{keywords=|found=TreeSet:[earth, science, universe], expected={length}:[3], valid=true|, isbn=|found=int[]:[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], expected={length}:[11], valid=true|}