void writeFactory(final FactoryDescriptor descriptor)
throws IOException {
JavaFileObject sourceFile = filer.createSourceFile(descriptor.name());
JavaWriter writer = new JavaWriter(sourceFile.openWriter());
String packageName = getPackage(descriptor.name()).toString();
writer.emitPackage(packageName)
.emitImports("javax.annotation.Generated");
writer.emitImports("javax.inject.Inject");
if (!descriptor.providerNames().isEmpty()) {
writer.emitImports("javax.inject.Provider");