* @param key the key to look up
     * @param defaultValue the default value to return if key is not found or value is blank
     * @return the value from the map or the default value
     */
    private String getValueFromMap(final Map<String, String> dataMap, final String key, final String defaultValue) {
        final String value = dataMap.get(key);
        if (StringUtil.isBlank(value)) {

   * {@code void}, {@code null} is returned.
   */
  @SuppressWarnings({
    "unchecked",
    "BooleanLiteral" // `(T) false` would produce an error
  })
  public static <T> @Nullable T defaultValue(Class<T> type) {
    checkNotNull(type);
    if (type.isPrimitive()) {
      if (type == boolean.class) {
        return (T) Boolean.FALSE;
      } else if (type == char.class) {

    throw new UnsupportedOperationException();
  }

  private <T> T pickInstance(T[] instances, T defaultValue) {
    return pickInstance(Arrays.asList(instances), defaultValue);
  }

  private <T> T pickInstance(Collection<T> instances, T defaultValue) {
    if (instances.isEmpty()) {
      return defaultValue;
    }
    // generateInt() is 1-based.

    /*
     * Even though it's weird to pass a defaultValue that is null, some callers do so. Those who
     * pass a literal "null" should probably just use `get`, but I would expect other callers to
     * pass an expression that *might* be null. This could happen with:
     *
     * - a `getFooOrDefault(@Nullable Foo defaultValue)` method that returns

     * PluginParameterExpressionEvaluator</a>.
     * @return the default value
     */
    @Nonnull
    String defaultValue() default "";

    /**
     * is the parameter required?
     * @return <code>true</code> if the Mojo should fail when the parameter cannot be injected
     */
    boolean required() default false;

    /**

    /**
     * Specifies the default value of the configuration property.
     *
     * @return the default value as a string, defaults to empty string
     */
    String defaultValue() default "";

    /**
     * Specifies whether the configuration property is read-only.
     *
     * @return true if the property is read-only, false otherwise
     */
    boolean readOnly() default false;

    /**
     * Retrieves a localized message for the given key.
     *
     * @param key the message key
     * @param defaultValue the default value to return if message not found
     * @return localized message or default value
     */
    public static String getMessage(final String key, final String defaultValue) {
        final Locale locale = LaRequestUtil.getOptionalRequest().map(HttpServletRequest::getLocale).orElse(Locale.ROOT);

    throw new UnsupportedOperationException();
  }

  private <T> T pickInstance(T[] instances, T defaultValue) {
    return pickInstance(Arrays.asList(instances), defaultValue);
  }

  private <T> T pickInstance(Collection<T> instances, T defaultValue) {
    if (instances.isEmpty()) {
      return defaultValue;
    }
    // generateInt() is 1-based.

    // We assume that all defaults are generics-safe, even if they aren't,
    // we take the risk.
    @SuppressWarnings("unchecked")
    T defaultValue = (T) defaults.getInstance(type.getRawType());
    if (defaultValue != null) {
      return defaultValue;
    }
    @SuppressWarnings("unchecked") // All arbitrary instances are generics-safe
    T arbitrary = (T) ArbitraryInstances.get(type.getRawType());

    }

    default String getSystemProperty(final String key, final String defaultValue) {
        return ComponentUtil.getSystemProperties().getProperty(key, System.getProperty(Constants.SYSTEM_PROP_PREFIX + key, defaultValue));
    }

    default void setSystemProperty(final String key, final String value) {
        if (value != null) {