We present an original approach for the automated computation of model-based test cases from specifications written in Java Modeling Language (JML). We aim at activating all the behaviors from the JML method specifications. Therefore, we extract each behavior and we compute the pertinent test data for the input parameters; we select the boundary values of the ordered domains, and we consider specific features for the objects, involving inheritance and aliasing. Finally, a preamble for each test case is computed by symbolic animation of the JML specification using constraint logic programming techniques. Thus, we are able to automatically generate executable Java test sequences to be run on the system under test. Moreover, this process requires the less possible intervention from a validation engineer.