* @param cause The cause of the exception.
     */
    public ContainerNotAvailableException(final String componentName, final Throwable cause) {
        super(componentName + " is not available.", cause);
        this.componentName = componentName;
    }

    /**
     * Constructor with cause only.
     * @param cause The cause of the exception.
     */

     * @return The component name
     */
    public String getComponentName() {
        return componentName;
    }

    /**
     * Sets the component name.
     * @param componentName The component name to set
     */
    public void setComponentName(final String componentName) {
        this.componentName = componentName;
    }

    /**
     * Returns the onDestroy listener.

        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.