Validation is a wide known process in programming.
Say for example that you want to check whether the provided objects meet some specified rules before using them or persisting them into a database.
In spring for example, validation included and may be used at any stage of the flow of the application.
I tried to think out of the box, and imagine a customized object-validation using java, using annotation over fields of a class, or using specified list of criteria without annotating the class to validate.
To do so, I kind of created a repository on github to validate objects.
You can check it over here, any suggestions are welcome.
Start the repo if you like it, and if you want to contribute create a pull/merge request.
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 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 annotationValidator = AnnotationValidator.getInstance(); 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:
Student student = new Student(); CriteriaValidator criteriaValidator = CriteriaValidator.getInstance(); Criteria criteria = new Criteria(); criteria.setObject(student); criteria.add(Criterion.of("name").is("mustapha")); criteria.add(Criterion.of("address").notNull()); criteria.add(Criterion.of("age").greaterOrEquals(4)); criteria.add(Criterion.of("phoneNumber").matches("\\d{10}")); student.setName("mustapha"); student.setAddress("wall street"); student.setAge(4); student.setPhoneNumber("1234567890"); System.out.println(criteriaValidator.getValidationReport(criteria)); assertTrue(criteriaValidator.check(criteria)); 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 criteriaValidator = CriteriaValidator.getInstance(); Criteria criteria = Criteria.of(student); criteria.add(Criterion.of("matters.maths").lessThan(20.0)); Matters matters = new Matters(); matters.setMaths(19.99); student.setMatters(matters); System.out.println(criteriaValidator.getValidationReport(criteria)); assertTrue(criteriaValidator.check(criteria)); ###### 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 criteriaValidator = CriteriaValidator.getInstance(); Criteria criteria = Criteria.of(book); criteria.add(Criterion.of("keywords").length(3)); criteria.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(criteriaValidator.getValidationReport(criteria)); assertTrue(criteriaValidator.check(criteria)); 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|} 
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