J8Validate is a small validation library that allows lambda expressions and method chaining to write concise and decoupled validation.
####Validation can remain stateless and safe to use dependancy injection or threads.
####J8ValidationResult's message property is now generic, so if one needs more than what is supplied out of the box, a custome class can be passed as the message
#####Creating a validator class: There are a few types to be aware of:
| Type | Description |
|---|---|
| AbstractJ8Validator | any validator class should inherit from this class |
| J8ValidationResult | holds errors and has various methods to be returned |
| J8When | returned by AbstractJ8Validator's from method. Filters objects to validate by predicate |
| J8Must | returned by J8When's methods. Takes a predicate to test objects validity |
| J8WithMessage | returned by J8Must. Adds a message to the errors if test fails. |
| J8WithSeverity | returned by J8WithMessage. Adds levels of severity to errors |
| J8ToValidate | returned by J8WithSeverity. Returns a J8ValidationResult object |
Step one: create a class to validate a type by inheriting from AbstractJ8Validator.
public class MyValidator extends AbstractJ8Validator<MyType>And create a method that returns a result:
public J8ValidationResult<String> validate(List<MyType> items, J8ValidationResult<String> result) {
return result;
}Step two: use the from method to validate the arguments passed into the validate method.
public J8ValidationResult<String> validate(List<MyType> items, J8ValidationResult<String> result) {
return
from(items, result)
.when(item -> item.isSomething() && item.values.Size() > 0)
.must(item -> item.getParent() != null)
.withMessage("Error: item(s) not valid.")
.critical()
.toValidate();
}#####Validation methods:
| Method | Description |
|---|---|
| from | object(s) to validate |
| when | filter based on a predicate or all |
| all | no filter |
| must | all objects should pass a predicate check |
| mustNot | No object should be true for the predicate |
| customMust | takes a boolean. Should be true |
| withMessage | add error message if failure |
| info | adds info severity if failure |
| warning | adds warning severity if failure |
| critical | adds critical severity if failure |
| fatal | adds fatal severity if failure |
| toValidate | returns a validation result |
customMust allows for more complicate validation that takes multiple arguments. Example:
from(list, result).all().customMust(veryComplexValidation(list, 3, 87, true, "propName"))
.withMessage("Warning: failed").warning().toValidate()##Example console program:
###Validator class
public class SnakeValidator extends AbstractJ8Validator<Snake> {
private final String dangerousSnakes = "Warning: dangerous snakes.";
public J8ValidationResult validateLists(List<Snake> snakes, List<Snake> petSnakes, J8ValidationResult<String> validationResult) {
J8ValidationResult<String> result =
from(petSnakes, validationResult)
.all()
.must(snake -> !snake.isVenomous())
.withMessage("Danger: pet snakes should not be venomous.")
.critical()
.toValidate();
result =
from(snakes, result)
.when(snake -> snake.isConstrictor())
.mustNot(snake -> snake.isVenomous())
.withMessage("Alert: snakes should not be both constrictors and venomous.")
.fatal()
.toValidate();
result =
from(snakes, result)
.all()
.mustNot(this::validateDangerousSnakes)
.withMessage("Warning: some snakes extremely lethal.")
.warning()
.toValidate();
result =
from(snakes, result)
.all()
.mustNot(snake -> snakes.size() + petSnakes.size() > 15)
.withMessage("I HAVE HAD IT WITH THESE m%th#rf^ck^&g SNAKES ON THIS m%th#rf^ck^&g PLANE")
.fatal()
.toValidate();
result = from(snakes, result)
.all()
.mustNot(snake -> snake.isVenomous())
.withMessage("Warning: some poisonous snakes.")
.warning()
.toValidate();
return result;
}
private boolean validateDangerousSnakes(Snake snake) {
if(snake.getLength() >= 10 && snake.isVenomous() || snake.isConstrictor()) return true;
return false;
}
}###Entry Point
public class Program {
public static void main(String[] args) throws Exception {
Program program = new Program();
List<Snake> snakes = new ArrayList<Snake>();
List<Snake> petSnakes = new ArrayList<Snake>();
for (int i = 0; i < 20; i++) {
Snake snake = new Snake();
snakes.add(new Snake());
if(snake.isVenomous()) continue;
petSnakes.add(snake);
}
SnakeValidator validator = new SnakeValidator();
J8ValidationResult<String> result = validator.validateLists(snakes, petSnakes, new J8ValidationResult<String>());
result.getErrorMessages().forEach(err -> System.out.println(err));
if(result.anyFatal()) {
handleSnakeProblem();
}
}
private static void handleSnakeProblem() {
System.out.println("eject...");
}
}###Snake class
public class Snake {
private boolean isVenomous;
private boolean isConstrictor;
private int length;
public boolean isVenomous() {
return isVenomous;
}
public boolean isConstrictor() {
return isConstrictor;
}
public int getLength() {
return length;
}
public Snake() {
Random rand = new Random();
length = rand.nextInt(12);
isVenomous = rand.nextInt(10) > 5? true : false;
isConstrictor = !isVenomous && rand.nextInt(10) > 5? true : false;
}
}
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