OWASP safetypes


Safetypes is a Java library, which aims to decrease the cost and effort for input validation for REST APIs.


The safetypes-java library contains special classes which can substitute their conventional alternatives in Java and which aid input validation on deserialization level, when used in a REST API implementation.


safetypes-java contains classes which can be used instead of String when declaring a request parameter:

//Spring REST example
import Word;
public ResponseEntity<String> word(@RequestParam Word word) {
return new ResponseEntity<>(word.get(), HttpStatus.OK);

The class Word is used instead of String and in the same time Word is constructed in such a way, that it allows only for letters, e.g. “abcd”, “test”, “Todor”, etc. and it throws an exception for everything else, e.g. “this is a test”, “number1”, “Ol3v”. From the API point of view, a correct and expected input will be successfully processed, while something incorrect or unexpected will lead to a Bad Request response.


The library contains useful classes ready to be used, but it is also easily extensible for customisation. Every special class in the library is in a hierarchy extending AbstractSafeType.java. This abstract class has two methods:

protected abstract void accept(T value) throws TypeValidationException;
protected void validate(T value) throws TypeValidationException { }

accept() must be implemented by any new special class, which is not part of the library, while validate() is intended to facilitate the customization of existing classes.


OWASP Java safetypes is free to use under the Apache License, Version 2.0.