There isn't a single jar to add, actually. And to figure out which specific jars you need, it actually depends on the JavaEE6 components that you are using. For example, if you need servlets, then you need to add jboss-servlet-api_3.0_spec.jar
However, If your project is Maven based then you can add a dependency to this (https://repository.jboss.org/nexus/content/groups/public/org/jboss/spec/jboss-javaee-6.0/1.0.0.Beta6/jboss-javaee-6.0-1.0.0.Beta6.pom)
<dependency>
<groupId>org.jboss.spec</groupId>
<artifactId>jboss-javaee-6.0</artifactId>
<version>1.0.0.Beta6</version>
<type>pom</type>
</dependency>
This will pull in the necessary set of Java EE6 spec jars.