Validator

Validator is a small, extensible API for performing validations on incoming data. Validator is built using the Strategy Pattern which makes it scalable and flexible in applying validations for Java based applications.

Configuring Validator

Configuring Validator to work in your project is easy. Simply download the API and copy the java\com folder into the source package of your project.

To change the package name of the API perform the following instruction:

Open the following file: com\example\helper\validate\ValidatorFactory.java and modify the String initializing packageName variable in ValidatorFactory.java from:

private String packageName = "com.example.helper.validate.";

to:

private String packageName = "com.companyname.helper.validate.";
// where "companyname" is the actual name of your company

That's all, we are done!

NB: Don't forget to rename your package to com\companyname\helper\validate

Using Validator

By default the API supports validation of the following data respective to their validation strategies

1. Emails => EmailValidator.java
2. Names => NameValidator.java
3. Phone numbers => PhoneValidator.java
4. Streets => StreetValidator.java
5. Zip codes => ZipcodeValidator.java
6. Address => AddressValidator.java

NB : The API does not guarantee that the default Perl Compatible Regular Expressions (PCREs) implemented in these validation strategies are comprehensive. You should implement appropriate PCREs that cater to the needs of the application you are building.

Inorder for the API to apply the appropriate validation strategy to your data you need to bind that data to a validation class. To bind your data to a validation strategy open com\example\helper\validate\ValidatorFactory.java and add a new binding in the static block:

static {
  Map<String, String> map = new HashMap<String, String>();
  map.put("firstname", "NameValidator");
  map.put("fieldToBeValidated" , "FooValidator");
  // other bindings ...
  validators = Collections.unmodifiableMap(map);
}

NB: The string "FooValidator" should literally represent a Java class that extends AbstractValidator.java and should override its method: boolean validate(final String subject);

Add the following code where you want to apply the validation:

... some code
ValidatorFactory validatorFactory = new ValidatorFactory();
Validator validator = validatorFactory.getValidator("fieldToBeValidated");
ValidatorContext validatorContext = new ValidatorContext(validator);
validatorContext.validate("fieldData");
// fieldData is the data associated with the field to be validated
... some code

NB: If you are working on a JavaEE application you might want to go through java\com\example\web\FormController.java which illustrates how to use the Validator API in a JavaEE environment using a Servlet as a naive example.

That's all folks.