SchemaGenTool interface:
package com.sun.jaxb_tck.lib;
public interface SchemaGenTool {
    /**
    * @param javaFiles  array of strings containing java files
    * @param outDir  output directory where schema file(s) will be generated
    * @param out  output stream for logging
    * @param err  error stream for logging
    * @return 0 if schema file(s) generated successfully
    */
    int generate(String[] javaFiles, File outDir,
            final PrintStream out, final PrintStream err) throws Exception;
}
Schema(s) generations should be accomplished during invocation of generate method.
The JAXB TCK includes the following class that is fully compatible with Sun's reference 
implementation and that can be used for schema generation: com.sun.jaxb_tck.lib.SchemaGen.
The realization of the method
generate(String[] javaFiles, File outDir, PrintStream out, PrintStream err)
generates xml schema(s) from java file(s).
If your implementation doesn't provide such a class, please, create it and specify it here.