Gson is an annotation based validation library used to validate java objects when converting to and from json strings using google's gson library.

• Use annotations to seperate validation logic from rest of your code
• Simple and lightweight library which doesn't get in the way
• Easy to and add custom annotations to fit your needs.

For now maven isn't supported, you can use jitpack but I would reccomend downloading as a jar and adding to your build path

Start by adding validation annotations to java fields.

class BasicObject { @Required String field; @Email String email; }

Then when validating the class, use the method GsonValidation#validate(Object obj);

BasicObject obj = new BasicObject(); obj.field = "value"; obj.email = 'email@example.com'; GsonValidator validator = new GsonValidator(obj); List<String> errors = validator.validate().catchErrors();

@Email - Validate an email. @Required - Makes the field required. Field cannot be missing. @PhoneNumber - Validate a phone number @Size(int min, int max) - Limit the min and max size of a number or string. Defaults are lowest/highest value for that data type. @Regex(String regex) - Run the validation tests against custom regex. Works on Strings only.

To make all fields required, enable requiredFields in the config

ValidationBuilder GsonValidator#validate(Object); //validates object to json String ValidationBuilder#toJson() throws ValidationException; //converts the data to json List<String> ValidationBuilder#validate(String, Class); //validates json to object 

MIT