As discussed in the JDO Overview, JDO uses a process called enhancement to prepare persistent classes for management by the JDO runtime. The Kodo JDO enhancer is a command-line tool that can be invoked via the included jdoc script or via its Java class, kodo.enhance.JDOEnhancer.
The enhancer accepts the standard set of command-line arguments defined by the configuration framework (see Section 2.3, “Command Line Configuration”), along with the following flags:
-directory/-d <output directory>: Path to the output directory. If the directory does not match the enhanced class' package, the package structure will be created beneath the directory. By default, the enhancer overwrites the original .class file.
Like the application identity tool, each additional argument to the enhancer must be either the full name of a persistent class, the .java file of a persistent class, the .class file of a persistent class, or a .jdo metadata file listing one or more persistent classes.
You can run the enhancer over classes that have already been enhanced, in which case it will not further modify the class. You can also run it over classes that are not persistence-capable, in which case it will treat the class as persistence-aware.
Note that the enhancement process for subclasses introduces dependencies on the persistent parent class being enhanced. This is normally not problematic; however, when running the enhancer multiple times over a subclass whose parent class is not yet enhanced, class loading errors can occur. In the event of a class load error, simply re-compile and re-enhance the offending classes.