• Jul 22, 2014

In yesterday's Framework-series post, I offhandedly mentioned that the "flashMessage" routine I use could easily be paired with or replaced by "toaster"-style notifications. This turned out to be very coincidental, as just today a NotesIn9 episode went up featuring Brad Balassaitis talking about using dGrowl for this purpose, along with an accompanying blog post.

Whenever I've used something like this, I've run into situations where I want to generate the message from the server, say as part of a partial refresh event to save an object. One option in that situation is to attach JavaScript to the "onComplete" and "onError" properties of the event handler (the latter of which is something I should do more regularly), but that doesn't give you access to all the information on the server that you may want to use in the message.

What I really want to do is send customized JavaScript code from the server back to the client, just for that event. Fortunately, there's an out-of-the-way method in the XPages stack to allow you to do this: UIViewRootEx#postScript. Though the documentation on that page is copious and detailed, it may not quite give you an indication of what that method does. What it does is to take a string of (client) JavaScript code that is then wrapped up and included in the currently-being-generated response to the browser, and which will be executed at the end of the current event (the partial refresh or, probably, initial page load). You can get to the view root object by resolving the "view" variable and casting it to an appropriate class:

UIViewRootEx2 view = (UIViewRootEx2)ExtLibUtil.resolveVariable(FacesContext.getCurrentInstance(), "view");

So I've used this in a couple situations, and here's an example of a method I have in my utils class for a current project. The project uses a WrapBootstrap theme that came with Gritter, which is a jQuery plugin for a similar effect, but it could be adapted for either Dojo module.

public static void toaster(final String summary, final String detail, final boolean sticky, final String styleClass) {
	StringBuilder result = new StringBuilder();
	result.append("jQuery.gritter.add({\n");
	if(StringUtil.isNotEmpty(summary)) {
		result.append("\ttitle: ");
		JSUtil.addString(result, summary);
		result.append(",\n");
	}
	if(StringUtil.isNotEmpty(detail)) {
		result.append("\ttext: ");
		JSUtil.addString(result, detail);
		result.append(",\n");
	}
	result.append("\tsticky: " + sticky + ",\n");
	
	String effectiveStyleClass = (styleClass == null ? "gritter-info" : styleClass);
	result.append("\tclass_name: ");
	JSUtil.addString(result, effectiveStyleClass);
	result.append("\n");
	
	result.append("})");

	FrameworkUtils.getViewRoot().postScript(result.toString());
}

So, first off: yikes. This is an example of why Java is awful at string handling and generating other languages. However, this ugliness is in service of a vital lesson that goes beyond this task:

Never, ever, ever generate code without proper escaping.

This is why it's so problematic to generate JSON or XML via view columns: formula language lacks escaping functions for those languages, and most code I've seen neglects to include its own. If you don't escape strings you're adding into another language, you're asking for parsing bugs at best and code-injection attacks at worst.

But back to the code at hand. I'm using the com.ibm.xsp.util.JSUtil class that comes with the XPages framework to assist in writing out JavaScript code. The result is that you can write something like this in Java:

toaster("Some alert!", "These are \"alert\" details", false, "gritter-error");

...and end up with code like this sent to the browser:

jQuery.gritter.add({
	title: "Some alert!",
	text: "These are \"alert\" details",
	sticky: false,
	class_name: "gritter-error"
})

In my example from yesterday, if I were using a partial refresh instead of a page redirection, I could use this method to alert the user of a successful save.

Because my model framework publishes FacesMessages for event conditions in a Faces environment, I've also written some companion methods to translate them into a toaster events and to drain the queue, useful during a partial refresh:

public static void toastMessage(final FacesMessage message) {
	String styleClass = null;
	if(FacesMessage.SEVERITY_ERROR.equals(message.getSeverity())) {
		styleClass = "gritter-error";
	} else if(FacesMessage.SEVERITY_FATAL.equals(message.getSeverity())) {
		styleClass = "gritter-error";
	} else if(FacesMessage.SEVERITY_INFO.equals(message.getSeverity())) {
		styleClass = "gritter-info";
	} else if(FacesMessage.SEVERITY_WARN.equals(message.getSeverity())) {
		styleClass = "gritter-warning";
	} else {
		styleClass = "gritter-success";
	}
	toaster(message.getSummary(), message.getDetail(), false, styleClass);
}
@SuppressWarnings("unchecked")
public static void toastMessages() {
	Iterator<FacesMessage> messages = FacesContext.getCurrentInstance().getMessages();
	while(messages.hasNext()) {
		FacesMessage message = messages.next();
		toastMessage(message);
	}
}

This sort of thing can be a useful way to bridge the client and server sides of the app without giving up client UI niceties.

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