MainArgsUtil.java

package co.codewizards.cloudstore.core.util;

import static co.codewizards.cloudstore.core.util.Util.*;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public final class MainArgsUtil {
// Logging is usually not yet initialised, when this class is used => commented out logger, it makes no sense.
//	private static final Logger logger = LoggerFactory.getLogger(MainArgsUtil.class);

	private MainArgsUtil() { }

	public static String[][] separateSystemPropertiesFromOtherArgs(String[] args) {
//		if (logger.isDebugEnabled())
//			logger.debug("separateSystemPropertiesFromOtherArgs: args={}", Arrays.toString(args));

		List<String> sysPropArgs = new ArrayList<String>(args.length);
		List<String> otherArgs = new ArrayList<String>(args.length);

		for (String arg : args) {
			if (arg.startsWith("-D"))
				sysPropArgs.add(arg);
			else
				otherArgs.add(arg);
		}
		return new String[][] {
			sysPropArgs.toArray(new String[sysPropArgs.size()]),
			otherArgs.toArray(new String[otherArgs.size()])
		};
	}

	public static String[] extractAndApplySystemPropertiesReturnOthers(String[] args) {
		String[][] sysPropArgsAndOtherArgs = separateSystemPropertiesFromOtherArgs(args);
		String[] sysPropArgs = sysPropArgsAndOtherArgs[0];
		String[] otherArgs = sysPropArgsAndOtherArgs[1];
		for (String arg : sysPropArgs) {
			if (!arg.startsWith("-D"))
				throw new IllegalStateException("sysPropArgs contains element not starting with '-D': " + arg);

			String kv = arg.substring(2);
			int equalsIndex = kv.indexOf('=');
			if (equalsIndex >= 0) {
				String k = kv.substring(0, equalsIndex);
				String v = kv.substring(equalsIndex + 1);
//				logger.debug("extractAndApplySystemPropertiesReturnOthers: k='{}' v='{}'", k, v);
				System.setProperty(k, v);
			}
			else {
//				logger.debug("extractAndApplySystemPropertiesReturnOthers: kv='{}'", kv);
				System.setProperty(kv, "");
			}
		}
		applyLocaleIfNeeded();
		return otherArgs;
	}

	/**
	 * (Re)Applies the {@linkplain Locale#setDefault(Locale) default locale}, if the
	 * system properties passed as normal program arguments cause a change.
	 * <p>
	 * Since the {@code Locale.default} property is already initialised (really early!),
	 * when {@link #extractAndApplySystemPropertiesReturnOthers(String[])} is called, the
	 * newly set system properties don't have any effect on the default {@code Locale}.
	 * Therefore, we must check the default {@code Locale}, now, and change it if needed.
	 */
	private static void applyLocaleIfNeeded() {
		final String userLanguage = System.getProperty("user.language");
		final String userCountry = System.getProperty("user.country");
		Locale locale = Locale.getDefault();
		if (! (equal(userLanguage, locale.getLanguage()) && equal(userCountry, locale.getCountry()))) {
			Locale.setDefault(new Locale(userLanguage, userCountry));
		}
	}
}