Java Validation Made Simple

Java framework for building strongly-typed validation.

Requirements

In order to use JVMS(Java Validation Made Simple), your project must be Java 8+.

Creating your first validator

In order to use the JVMS validation you just need to import it:

import static com.persoft.validation.JVMS.*;

Then imagine that you need to validate a field to not be null or empty:

ValidationResult validationResult = notBlank().validate(firstName);
if(!validationResult.isValid()) {
    System.out.println(validationResult.getMessage());
}

In this example we use the built in validation notBlank , then we tell JVMS which field we want to validate with the validate method.

The validate method returns a ValidationResult object that contains:

• isValid() - a boolean that says whether the validation succeeded.
• getMessage() - a String which contains the error message.

Chaining validators

You can chain multiple validators together for the same property:

ValidationResult validationResult = notNull()
        .and(notEmpty())
        .and(notEqual("foo"))
        .validate(firstName);

Throwing Exceptions

Instead of returning a ValidationResult, you can tell JVMS to throw an exception if validation fails by using the throwIfInvalid method:

notBlank().validate(firstName).throwIfInvalid();

You just need to catch ValidationException

throwIfInvalid() method will throw an exception with default error message. You can customize that error message by passing the parameter name or by using a custom one:

// Example error: Must not be null.
notBlank().validate(firstName).throwIfInvalid();

// Example error: firstName : Must not be null.
notBlank().validate(firstName).throwIfInvalid("firstName");

// Example error: Firstname is required!
notBlank().validate(firstName).throwIfInvalidCustomMessage("Firstname is required!");

Customizing the error message

getMessage will return a default error message if validation fails. You can customize that error message by passing the parameter name or by using a custom one:

// Example error: firstName : Must not be null.
notBlank().validate(firstName).withMessage("firstName");

// Example error: Firstname is required!
notBlank().validate(firstName).withCustomMessage("Firstname is required!");

Creating custom validation

Here is an example of an Employee class custom validation:

Employee class:

public class Employee {
    private String firstName;
    private String zipCode;   
    //Assume getters & setters below.
}

Custom validation rules:

GenericValidation<Employee> firstNameRule = GenericValidation.from(
        e -> (e.getFirstName() != null && !e.getFirstName().isEmpty()),
        "FirstName is required!"
);

GenericValidation<Employee> zipCodeNotEmptyRule = GenericValidation.from(
    e -> (e.getZipCode() != null && !e.getZipCode().isEmpty()),
    "Zip code is required"
);

Employee employee = new Employee();
firstNameRule.and(zipCodeNotEmptyRule).validate(employee).throwIfInvalid();

The example above will throw ValidationException with exception message - 'FirstName is required!'

Built-in Validators

JVSM ships with several built-in validators.

notNull Validator

Description: Ensures that the specified property is not null.

Example:

notNull().validate(firstName);

Example error: must not be null.

notEmpty Validator

Description: Ensures that the specified property is not an empty string or whitespace.

Example:

notEmpty().validate(firstName);

Example error: should not be empty.

notBlank Validator

Description: Ensures that the specified property is not null or empty.

Example:

notBlank().validate(firstName);

Example error: must not be null / should not be empty.

isEqual Validator

Description: Ensures that the value of the specified property is equal to a particular value.

Example:

isEqual("Foo").validate(firstName);

Example error: should be equal to 'Foo'.

notEqual Validator

Description: Ensures that the value of the specified property is not equal to a particular value.

Example:

notEqual("Foo").validate(firstName);

Example error: should not be equal to 'Foo' .

length Validator

Description: Ensures that the length of a particular string property is within the specified range. However, it doesn’t ensure that the string property isn’t null.

Example:

length(1, 250).validate(firstName);

Example error: must be between 1 and 250 characters. Note: Only valid on string properties.

maxLength Validator

Description: Ensures that the length of a particular string property is no longer than the specified value.

Example:

maxLength(10).validate(firstName);

Example error: must be 10 characters or fewer. Note: Only valid on string properties.

minLength Validator

Description: Ensures that the length of a particular string property is longer than the specified value.

Example:

minLength(10).validate(firstName);

Example error: must be at least 10 characters. Note: Only valid on string properties.

lessThan Validator

Description: Ensures that the value of the specified property is less than a particular value.

Example:

lessThan(10).validate(age);

Example error: must be less than 10. Note: Only valid on number properties.

lessThanOrEqual Validator

Description: Ensures that the value of the specified property is less than or equal to a particular value.

Example:

lessThanOrEqual(10).validate(age);

Example error: must be less than or equal to 10. Note: Only valid on number properties.

greaterThan Validator

Description: Ensures that the value of the specified property is greater than a particular value.

Example:

greaterThan(10).validate(age);

Example error: must be greater than 10. Note: Only valid on number properties.

greaterThanOrEqual Validator

Description: Ensures that the value of the specified property is greater than or equal to a particular value.

Example:

greaterThanOrEqual(10).validate(age);

Example error: must be greater than or equal to 10. Note: Only valid on number properties.

matches Validator

Description: Ensures that the value of the specified property matches the given regular expression.

Example:

matches("some regex").validate(email);

Example error: is not in the correct format. Note: Only valid on string properties.

isEmail Validator

Description: Ensures that the value of the specified property is a valid email address format.

Example:

isEmail().validate(email);

Example error: is not a valid email address. Note: Only valid on string properties.

must Validator

Description: Accepting a user defined predicate.

Example:

must(s -> s.equals("test")).validate(firstName);

Example error: not matching the predicate defined.

isCreditCardNumber Validator

Description: Validating a credit card number - visa, mastercard, discover, american express, diners, jcb.

Example:

isCreditCardNumber().validate(cardNumber);

Example error: is not a valid credit card number.

Authors

• Petar Petrov - Initial work - Petrakus

See also the list of contributors who participated in this project.