#vulnerable code 
                             @Override
	public void apply(FaceletContext context, UIComponent parent) throws IOException {
		if (!ComponentHandler.isNew(parent)) {
			return;
		}

		if (!TRUE.equals(getApplicationAttribute(context.getFacesContext(), Socket.class.getName()))) {
			throw new IllegalStateException(ERROR_ENDPOINT_NOT_ENABLED);
		}

		String channelName = channel.isLiteral() ? channel.getValue(context) : null;

		if (channelName == null || !PATTERN_CHANNEL.matcher(channelName).matches()) {
			throw new IllegalArgumentException(String.format(ERROR_INVALID_CHANNEL, channelName));
		}

		Object userObject = getObject(context, user);

		if (userObject != null && !(userObject instanceof Serializable)) {
			throw new IllegalArgumentException(String.format(ERROR_INVALID_USER, userObject));
		}

		SocketChannelManager channelManager = getReference(SocketChannelManager.class);
		String scopeName = (scope == null) ? null : scope.isLiteral() ? getString(context, scope) : "";
		String channelId;

		try {
			channelId = channelManager.register(channelName, scopeName, (Serializable) userObject);
		}
		catch (IllegalArgumentException ignore) {
			throw new IllegalArgumentException(String.format(ERROR_INVALID_SCOPE, scopeName));
		}

		if (channelId == null) {
			throw new IllegalArgumentException(String.format(ERROR_DUPLICATE_CHANNEL, channelName));
		}

		Integer portNumber = getObject(context, port, Integer.class);
		String onopenFunction = getString(context, onopen);
		String onmessageFunction = onmessage.getValue(context);
		String oncloseFunction = getString(context, onclose);
		String functions = onopenFunction + "," + onmessageFunction + "," + oncloseFunction;
		ValueExpression connectedExpression = getValueExpression(context, connected, Boolean.class);

		SystemEventListener listener = new SocketFacesListener(portNumber, channelName, channelId, functions, connectedExpression);
		subscribeToViewEvent(PostAddToViewEvent.class, listener);
		subscribeToViewEvent(PreRenderViewEvent.class, listener);
	} 
                            #location 28 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Override
	public void apply(FaceletContext context, UIComponent parent) throws IOException {
		if (!ComponentHandler.isNew(parent)) {
			return;
		}

		if (!TRUE.equals(getApplicationAttribute(context.getFacesContext(), Socket.class.getName()))) {
			throw new IllegalStateException(ERROR_ENDPOINT_NOT_ENABLED);
		}

		Integer portNumber = getObject(context, port, Integer.class);
		String channelName = getChannelName(context, channel);
		String channelId = getChannelId(context, channelName, scope, user);
		String functions = getString(context, onopen) + "," + onmessage.getValue(context) + "," + getString(context, onclose);
		ValueExpression connectedExpression = getValueExpression(context, connected, Boolean.class);

		SystemEventListener listener = new SocketFacesListener(portNumber, channelName, channelId, functions, connectedExpression);
		subscribeToViewEvent(PostAddToViewEvent.class, listener);
		subscribeToViewEvent(PreRenderViewEvent.class, listener);
	}