private String componentName;

    /**
     * Constructor with component name.
     * @param componentName The name of the component that is not available.
     */
    public ContainerNotAvailableException(final String componentName) {
        super(componentName + " is not available.");
        this.componentName = componentName;
    }

    /**

        String second = "second";
        String componentName = "testComponent";

        ComponentUtil.register(first, componentName);
        String retrieved1 = ComponentUtil.getComponent(componentName);
        assertSame(first, retrieved1);

        ComponentUtil.register(second, componentName);
        String retrieved2 = ComponentUtil.getComponent(componentName);
        assertSame(second, retrieved2);
    }

     * @param regex The regular expression to match URLs.
     * @param componentName The name of the component to register.
     */
    public synchronized void register(final String regex, final String componentName) {
        clientMap.put(regex, componentName);
        clientFactoryList.forEach(f -> load(f, regex, componentName));
    }

    /**
     * Loads a crawler client into the specified crawler client factory.