in freemarker-generator-base/src/main/java/org/apache/freemarker/generator/base/datasource/DataSourceFactory.java [164:175]
public static DataSource fromEnvironment(String name, String group, String contentType) {
try {
final Properties properties = PropertiesFactory.create(System.getenv());
final StringWriter writer = new StringWriter();
properties.store(writer, null);
final StringDataSource dataSource = new StringDataSource(name, writer.toString(), contentType, UTF_8);
final URI uri = UriUtils.toUri(Location.ENVIRONMENT, "");
return create(name, group, uri, dataSource, contentType, UTF_8, noProperties());
} catch (IOException e) {
throw new RuntimeException("Unable to load environment variables", e);
}
}