A motivation of MDA (model driven architecture) is to use models as programs so as to increase the abstract level of software development. Design patterns provide reusable constructs that can be introduced into MDA to increase the modeling granularity as well as the reusability of model transformation rules. This can be achieved by applying design patterns as the integrated development units in MDA, which raises two problems of modeling and model transforming. First, patterns should be used as integrated modeling units. Second, pattern models should be transformed by applying pattern transformation rules built on the pattern units. To solve these two problems, a solution is to define pattern unit metamodel for each pattern and to provide the EJB model transformation rules basing on each pattern unit metamodel respectively. In this way, patterns can be used as integrated modeling units by instantiating the pattern metamodel units, and then the pattern models can be transformed into the EJB models by applying the transformation rules. This paper also demonstrates how to extend MOF (meta object facility) meta-metamodels to define the pattern specifications and how to define the transformation rules to map the pattern models as well as related business models onto the EJB platform.