I want to autogenerate some java classes from interfaces. My first thought was to write a code generator, and integrate it as a maven plugin.
I was thinking of creating a maven plugin with a codegen goal that is called during the build process.
So if I choose this route, how do I provide the plugin with the interfaces to be processed? And where should the generated files go?
Are there any existing plugins that can be configured to generate default class implementations?
Maybe have a look at the XDoclet Maven plugin- XDoclet is often used for generating sources from doclet-style markup in classes (e.g. autogenerating MBean interfaces from implementations) and that sounds similar to what you're doing.
Sources should go in {project.build.directory}/generated-sources
Most plugins take configuration passed through the plugin configuration section in the pom. You can use default values as well, or an annotation and classpath scanning.
A plugin like the maven-jspc-plugin generates code, which you could take a look at. The "Better Builds With Maven" e-book also contains a reasonably comprehensive chapter on writing plugins.