These classes provide various implementations of the StockPrice API. To compile these classes, you must have a JPA implementation. In your environment, please set JAVAX_PERSISTENCE to the path to the jar file containing the JPA API classes, e.g. export JAVA_PERSISTENCE=/path_to/javax.persistence.jar For examples that require Eclipselink-specific functionality, set ECLIPSELINK_JAR to the path of the eclipselink implementation, e.g. export ECLIPSELINK_JAR=/path_to/eclipselink.jar There are several implementations of the stock price API, discussed mostly in Chapter 11, as the implementation differences affect JPA. The choice of those implementations is selected via -Dimpl value passed to the ant comandline: -Dimpl=LazyLazyImpl (both relationships are annotated lazy) -Dimpl=EagerLazyImpl (the OneToMany stock->options relationship is eager) -Dimpl=EagerEagerImpl (both relationships are eager) -Dimpl=LazyEagerImpl (the ManyToOne options->stock relationship is eager) For tests with the mock entity manager, use LazyLazyImpl, which is the default.