javax.validation is missing.
You'll find a jar here. If you use Maven, this is the dependency:
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.0.0.GA</version>
</dependency>
For validation to actually work, you need an implementation as well, such as Hibernate Validator. Maven dependency:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>4.0.2.GA</version>
<scope>runtime</scope>
</dependency>
The JSR reference means that this is a standard developed by the Java Community Process, specifically JSR number 303.