SystemPropertyUtil Class — netty Architecture

Source Code

common/src/main/java/io/netty/util/internal/SystemPropertyUtil.java lines 29–185

public final class SystemPropertyUtil {

    private static final InternalLogger logger = InternalLoggerFactory.getInstance(SystemPropertyUtil.class);

    /**
     * Returns {@code true} if and only if the system property with the specified {@code key}
     * exists.
     */
    public static boolean contains(String key) {
        return get(key) != null;
    }

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}, while falling back to {@code null} if the property access fails.
     *
     * @return the property value or {@code null}
     */
    public static String get(String key) {
        return get(key, null);
    }

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}, while falling back to the specified default value if
     * the property access fails.
     *
     * @return the property value.
     *         {@code def} if there's no such property or if an access to the
     *         specified property is not allowed.
     */
    public static String get(final String key, String def) {
        checkNonEmpty(key, "key");

        String value = null;
        try {
            if (System.getSecurityManager() == null) {
                value = System.getProperty(key);
            } else {
                value = AccessController.doPrivileged(new PrivilegedAction<String>() {
                    @Override
                    public String run() {
                        return System.getProperty(key);
                    }
                });
            }
        } catch (SecurityException e) {
            logger.warn("Unable to retrieve a system property '{}'; default values will be used.", key, e);
        }

        if (value == null) {
            return def;
        }

        return value;
    }

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}, while falling back to the specified default value if
     * the property access fails.
     *
     * @return the property value.
     *         {@code def} if there's no such property or if an access to the
     *         specified property is not allowed.
     */
    public static boolean getBoolean(String key, boolean def) {
        String value = get(key);
        if (value == null) {
            return def;
        }

        value = value.trim().toLowerCase();
        if (value.isEmpty()) {
            return def;
        }

        if ("true".equals(value) || "yes".equals(value) || "1".equals(value)) {
            return true;
        }