A JSON Schema validation implementation in pure Java, which aims for correctness and performance, in that order
Hibernate Validator - Bean Validation 2.0 (JSR 380) Reference Implementation
A Java validation framework leveraging fluent interface style and JSR 303 specification
OVal - the object validation framework for Java
Governator is a library of extensions and utilities that enhance Google Guice to provide: classpath scanning and automatic binding, lifecycle management, configuration to field mapping, field validation and parallelized object warmup.
This is a burp intruder extender that is designed for automation and validation of XSS vulnerabilities.
Industry supported, open source PDF/A validation library
Schema validation and conversion based on RELAX NG
A library that extends the Java Bean Validation with additional @Annotations.