kamikazbee

Kamikazbee is a java 8 library that serves a single purpose! Validate java objects.

The core object of the library is the Validator which takes a list of validation rules that should be applied and validates a given object. A validation rule is the check to be performed on a given object.

Kamikazbee comes with some stock rules but you can also easily create your own custom ones.

Stock validation rules

Empty

Validates that a String value is not null or an empty (trimmed) String

Length

Validates that a given String matches the given criteria regarding its length.

Options

• min - the minimum characters for the value to have (inclusive)
• max - the maximum characters for the value to have (inclusive)
• exact - the exact number of characters for the value to be

NonNull

Validates that a given object is not null

Quantity

Validates that a given Number matches the given criteria

Options

• min - the minimum value (inclusive)
• max - the max value (inclusive)
• exact - the exact value

Pattern

Validates that a given String matches a regex pattern (check Pattern)

Options

• pattern - the pattern to be matched
• flags - the regex flags to be used

Example

For this example lets consider the following very base schema:

public class Person {
  private String firstName;
  private String lastName;
  private String sex;
  private Address address;
  private List<Pet> pets;
  
  // getters and setters omitted for simplicity

}

public class Address {
  private String country;
  private String state;
  private String city;
  private String street;
  private int number;
  
  // getters and setters omitted for simplicity
}

public class Pet {
  private String name;
  private String species;
  
  // getters and setters omitted for simplicity
}

Now lets suppose we want to make the following validations:

• Person#firstName should not be empty and if an error happens place it in the "base" field
• Person#sex must be between 0 and 6 characters if it exists
• Person#address must not be null and if it is null it should stop the validation
• Address#city should not be empty with a custom error message
• Address#number must be greater than or equal to one
• Pet#name should not be empty

We can achieve all the above with the following code:

Person person = createPerson(); // suppose this creates a Person with some data

Validator<Address> addressValidator = new Validator<>()
  .addRule(empty().message("City is required"), Address:getCity, "city")
  .addRule(quantity().min(1), Address::getNumber, "number");
  
Validator<Pet> petValidator = new Validator<>()
  .addRule(empty(), Pet::getName, "name");

ValidationResult result = new Validator<Person>()
  .addRule(empty(), Person::getFirstName)
  .addRule(length().min(0).max(6).optional(true), Person::getSex, "sex")
  .addRule(nonNull().blocking(true), Person::getAddress, "address")
  .addNestedValidator(addressValidator, Person::getAddress, "address")
  .addListValidator(new Validator<Pet>(), Person::getPets, "pets");
  
  
// Lets suppose that in order to keep it simple we are simply printing to console
if (result.isValid()) {
  System.out.println("Yay, our data are valid!!");
} else {
  System.out.println("Your data are not valid:");
  
  // This will return a Map with the validation errors
  System.out.println(result.getErrors());
}

Create your own validation rule

Well that is all good but what happens if I want to add some custom validation logic? What if I want to validate that the Address number field is a multiple of 3? We can create a new validation rule for that as follows:

public class MultipleOfThreeRule extends RuleImpl<Integer, MultipleOfThreeRule> {

  MultipleOfThreeRule() {
    message("Must be a multiple of 3"); // Add a default message
  }
  
  @Override
  protected Predicate<Integer> getValidation() {
    return i -> i % 3 == 0;
  }
  
}

Great!! You now have a custom Rule that check whether an Integer is a multiple of 3 that can be used like:

   ...
   .addRule(new MultipleOfThreeRule(), Address:getNumber, "number");

But wait what happens if I want to make my rule more generic and pass the number for the mod as an option? Then you have to make your Rule a bit different, like this:

public class MultipleOfRule extends RuleImpl<Integer, MultipleOfRule> {

  private int number;
  
  public MultipleOfRule number(int number) {
    this.number = number;
    return this;
  }
  
  @Override
  protected Predicate<Integer> getValidation() {
    return i -> i % number == 0;
  }
  
  @Override
  protected String getMessage() {
    // Get the message from super in order to return a custom message if given instead of the default
    String superMessage = super.getMessage();
    if(superMessage != null) {
      return superMessage;
    } else {
      return "Must be a multiple of " + number;
    }
  }
  
}

You can then do the following:

   ...
   .addRule(new MultipleOfRule().number(5), Address:getNumber, "number");

Download

We are on Maven Central.

Use with gradle

compile 'com.github:kamikazbee:0.1.0'

Use with maven

<dependency>
    <groupId>com.github</groupId>
    <artifactId>kamikazbee</artifactId>
    <version>0.1.0</version>
</dependency>