A java class generator out of properties file - mainly for oVirt resources files but can be tweaked to create any class

AppErrorsGenerator.java

package org.ovirt.engine.common;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.nio.file.FileSystems;
import java.util.Map;
import java.util.Properties;

import com.google.gwt.i18n.client.Constants;
import com.google.gwt.i18n.client.ConstantsWithLookup;
import com.sun.codemodel.JAnnotationUse;
import com.sun.codemodel.JClassAlreadyExistsException;
import com.sun.codemodel.JCodeModel;
import com.sun.codemodel.JDefinedClass;
import com.sun.codemodel.JMethod;

public class AppErrorsCreator {

    public static final String PACKAGE = System.getProperty("generated.apperrors.packageName");
    public static final String CLASS_NAME = System.getProperty("generated.apperrors.className");

    private static void from(Properties props) throws JClassAlreadyExistsException, IOException {
        JCodeModel codeModel = new JCodeModel();
        JDefinedClass definedClass = codeModel._class(PACKAGE + "." + CLASS_NAME);

        // class definition
        definedClass._extends(ConstantsWithLookup.class);

        // created methods
        for (Map.Entry<Object, Object> entry : props.entrySet()) {
            JMethod method = definedClass.method(
                    Method.PUBLIC,
                    String.class,
                    stripKey(entry));
            //annotate
            JAnnotationUse annotate = method.annotate(Constants.DefaultStringValue.class);
            annotate.param("value", entry.getValue().toString());
        }

        //build class
        codeModel.build(FileSystems.getDefault().getPath(
                System.getProperty("generated.apperrors.targetDir")).toFile());
    }

    private static String stripKey(Map.Entry<Object, Object> entry) {
        return entry.getKey().toString().replace(".", "_");
    }

    /**
     * create the AppErrors java class. use the system properties documented in the pom.xml
     * @throws IOException
     * @throws JClassAlreadyExistsException
     */
    public static void main(String... args) throws IOException, JClassAlreadyExistsException {
        from(loadAppErrors());
    }

    private static Properties loadAppErrors() throws IOException {
        Properties props = new Properties();
        InputStream resource = props.getClass().getResource(
                System.getProperty("source.apperrors")).openStream();
        System.out.printf("\nresource ----%s %s\n", System.getProperty("source.apperrors"), resource);
        props.load(resource);
        return props;
    }
}