What are the main disadvantages of Java Server Faces 2.0?

Question

JSF 2.0 disadvantages? Honestly, apart from the relative steep learning curve when you don't have a solid background knowledge about basic Web Development (HTML/CSS/JS, server side versus client side, etc) and the basic Java Servlet API (request/response/session, forwarding/redirecting, etc), no serious disadvantages comes to mind. JSF in its current release still needs to get rid of the negative image it gained during the early ages, during which there were several serious disadvantages.

JSF 1.0 (March 2004)

This was the initial release. It was cluttered with bugs in both the core and performance areas you don't want to know about. Your webapplication didn't always work as you'd intuitively expect. You as developer would run hard away crying.

JSF 1.1 (May 2004)

This was the bugfix release. The performance was still not much improved. There was also one major disadvantage: you can't inline HTML in the JSF page flawlessly. All plain vanilla HTML get rendered before the JSF component tree. You need to wrap all plain vanilla in <f:verbatim> tags so that they get included in the JSF component tree. Although this was as per the specification, this has received a lot of criticism. See also a.o. JSF/Facelets: why is it not a good idea to mix JSF/Facelets with HTML tags?

JSF 1.2 (May 2006)

This was the first release of the new JSF development team lead by Ryan Lubke. The new team did a lot of great work. There were also changes in the spec. The major change was the improvement of the view handling. This not only fully detached JSF from JSP, so one could use a different view technology than JSP, but it also allowed developers to inline plain vanilla HTML in the JSF page without hassling with <f:verbatim> tags. Another major focus of the new team was improving the performance. During the lifetime of the Sun JSF Reference Implementation 1.2 (which was codenamed Mojarra since build 1.2_08, around 2008), practically every build got shipped with (major) performance improvements next to the usual (minor) bugfixes.

The only serious disadvantage of JSF 1.x (including 1.2) is the lack of a scope in between the request and session scope, the so-called conversation scope. This forced developers to hassle with hidden input elements, unnecessary DB queries and/or abusing the session scope whenever one want to retain the initial model data in the subsequent request in order to successfully process validations, conversions, model changes and action invocations in the more complex webapplications. The pain could be softened by adopting a 3rd party library which retains the necessary data in the subsequent request like MyFaces Tomahawk <t:saveState> component, JBoss Seam conversation scope and MyFaces Orchestra conversation framework.

Another disadvantage for HTML/CSS purists is that JSF uses the colon : as ID separator character to ensure uniqueness of the HTML element id in the generated HTML output, especially when a component is reused more than once in the view (templating, iterating components, etc). Because this is an illegal character in CSS identifiers, you would need to use the \ to escape the colon in CSS selectors, resulting in ugly and odd-looking selectors like #formId\:fieldId {} or even #formId\3A fieldId {}. See also How to use JSF generated HTML element ID with colon ":" in CSS selectors? However, if you're not a purist, read also By default, JSF generates unusable ids, which are incompatible with css part of web standards.

Also, JSF 1.x didn't ship with Ajax facilities out of the box. Not really a technical disadvantage, but due to the Web 2.0 hype during that period, it became a functional disadvantage. Exadel was early to introduce Ajax4jsf, which was thoroughly developed during the years and became the core part of JBoss RichFaces component library. Another component libraries were shipped with builtin Ajax powers as well, the well known one being ICEfaces.

About halfway the JSF 1.2 lifetime, a new XML based view technology was introduced: Facelets. This offered enormous advantages above JSP, especially in the area of templating.

JSF 2.0 (June 2009)

This was the second major release, with Ajax as buzzword. There were a lot of technical and functional changes. JSP is replaced by Facelets as the default view technology and Facelets was expanded with capabilities to create custom components using pure XML (the so-called composite components). See also Why Facelets is preferred over JSP as the view definition language from JSF2.0 onwards?

Ajax powers were introduced in flavor of the <f:ajax> component which has much similarities with Ajax4jsf. Annotations and convention-over-configuration enhancements were introduced to kill the verbose faces-config.xml file as much as possible. Also, the default naming container ID separator character : became configurable, so HTML/CSS purists could breathe relieved. All you need to do is to define it as init-param in web.xml with the name javax.faces.SEPARATOR_CHAR and ensuring that you aren't using the character yourself anywhere in client ID's, such as -.

Last but not least, a new scope was introduced, the view scope. It eliminated another major JSF 1.x disadvantage as described before. You just declare the bean @ViewScoped to enable the conversation scope without hassling all ways to retain the data in subsequent (conversational) requests. A @ViewScoped bean will live as long as you're subsequently submitting and navigating to the same view (independently of the opened browser tab/window!), either synchronously or asynchronously (Ajax). See also Difference between View and Request scope in managed beans and How to choose the right bean scope?

Although practically all disadvantages of JSF 1.x were eliminated, there are JSF 2.0 specific bugs which might become a showstopper. The @ViewScoped fails in tag handlers due to a chicken-egg issue in partial state saving. This is fixed in JSF 2.2 and backported in Mojarra 2.1.18. Also passing custom attributes like the HTML5 data-xxx is not supported. This is fixed in JSF 2.2 by new passthrough elements/attributes feature. Further the JSF implementation Mojarra has its own set of issues. Relatively a lot of them are related to the sometimes unintuitive behaviour of <ui:repeat>, the new partial state saving implementation and the poorly implemented flash scope. Most of them are fixed in a Mojarra 2.2.x version.

Around the JSF 2.0 time, PrimeFaces was introduced, based on jQuery and jQuery UI. It became the most popular JSF component library.

JSF 2.2 (May 2013)

With the introduction of JSF 2.2, HTML5 was used as buzzword even though this was technically just supported in all older JSF versions. See also JavaServer Faces 2.2 and HTML5 support, why is XHTML still being used. Most important new JSF 2.2 feature is the support for custom component attributes, hereby opening a world of possibilities, such as custom tableless radio button groups.

Apart from implementation specific bugs and some "annoying little things" such as inability to inject an EJB in a validator/converter (already fixed in JSF 2.3), there are not really major disadvantages in the JSF 2.2 specification.

Component based MVC vs Request based MVC

Some may opt that the major disadvantage of JSF is that it allows very little fine-grained control over the generated HTML/CSS/JS. That's not JSF's own, that's just because it's a component based MVC framework, not a request (action) based MVC framework. If a high degree of controlling the HTML/CSS/JS is your major requirement when considering a MVC framework, then you should already not be looking at a component based MVC framework, but at a request based MVC framework like Spring MVC. You only need to take into account that you'll have to write all that HTML/CSS/JS boilerplate yourself. See also Difference between Request MVC and Component MVC.

See also:

• What is the difference between JSF, Servlet and JSP? (just to understand the basics)
• Using JSF to develop tableless CSS layouts (another myth about JSF)
• JSF vs plain HTML/CSS/JS/jQuery (when JSF is the wrong choice)
• Design patterns in web applications (illustrates the ideology behind MVC)

After 5 years of working with JSF, I think that I can add my 2 cents.

Two major JSF drawbacks:

1. Big learning curve. JSF is complex, that's just true.
2. Its component nature. Component-based framework tries to hide the true nature of the Web, which comes with a huge amount of complications and disasters (like not supporting GET in JSF within almost 5 years).
   IMHO hiding HTTP Request/Response from the developer is an enormous mistake. From my experience, every component-based framework adds abstraction to the Web development, and that abstraction results in unnecessary overhead and higher complexity.

And minor drawbacks that come to my mind:

1. By default ID of the object is composed of its parents' ids, for example form1:button1.
2. No easy way to comment-out incorrect page's fragment. Tag <ui:remove> needs syntactically correct content which is parsed anyway.
3. Low quality 3rd party components which e.g. don't check isRendered() inside processXxx() method before continuing.
4. Incorporating LESS & Sencha is hard.
5. Doesn't play well with REST.
6. Not so easy for UX designers, because ready-to-use components have their own CSS styles, that need to be overwritten.

Don't get me wrong. As a component framework JSF in version 2 is really good, but it's still component-based, and always will be...

Please take a look at the low popularity of Tapestry, Wicket and low enthusiasm of experienced JSF developers (what is even more meaningful). And for contrast, take a look at the success of Rails, Grails, Django, Play! Framework - they all are action-based and don't try to hide from the programmer true request/response and stateless nature of the web.

For me it's major JSF disadvantage. IMHO JSF can suits some type of applications (intranet, forms-intensive), but for real-life web application it's not a good way to go.

Hope it helps somebody with his/her choices that regards to front-end.

A few drawbacks that pop to mind:

1. JSF is a component-based framework. This has inherent restrictions that have to do with obeying the component-model.
2. AFAIK JSF supports only POST, so if you want a GET somewhere you have to do a plain servlet/JSP.
3. Most components try to provide abstractions over domains like relational databases and front-end JavaScript, and many time these abstractions are "leaky" and very hard to debug.
4. These abstractions might be a good starting point for a junior developer or someone not comfortable with a particular domain (e.g. front-end JavaScript), but are very hard to optimise for performance, since there are several layers involved, and most people that use them have little understanding of what is going on under the hood.
5. The templating mechanisms that are usually used with JSF have nothing to do with how web desigers work. The WYSIWYG editors for JSF are primitive and in any case, your designer will give you HTML/CSS that you'll have to spend ages converting.
6. Things like EL expressions are not statically checked and both the compiler and IDEs are not doing a good job at finding errors, so you'll end up with errors that you'll have to catch at run-time. This might be fine for dynamically typed language like Ruby or PHP, but if I have to withstand the sheer bloat of the Java ecosystem, I demand typing for my templates.

To sum up: The time you will save with JSF, from avoiding to write the JSP/servlet/bean boilerplate code, you'll spent it x10 to make it scale and do exactly what you want it to do.

To me the biggest disadvantage of JSF 2.0 is the learning curve not only of JSF, but the component libraries that you have to use in order to get it to do useful work. Consider the staggering number of specifications and standards you have deal with to really be proficient:

• HTML in the various incarnations. Don't pretend you don't need to know it.
• HTTP -- when you can't figure out what is going on you have to open Firebug and see. For that you need to know this.
• CSS -- Like it or not. It isn't so bad really and there are some nice tools out there at least.
• XML -- JSF will probably the first place you use namespaces to this degree.
• Servlet Specification. Sooner or later you will get into calling methods in this package. Aside from that you have to know how your Facelets gets turned into XHTML or whatever.
• JSP (mostly so you know why you don't need it in JSF)
• JSTL (again, mostly to cope with legacy framework)
• Expression Language (EL) in its various forms.
• ECMAScript, JavaScript, or whatever else you want to call it.
• JSON -- you should know this even if you don't use it.
• AJAX. I would say JSF 2.0 does a decent job of hiding this from you but you still need to know what is going on.
• The DOM. And how a browser uses it. See ECMAScript.
• DOM Events -- a topic all by itself.
• Java Persistence Architecture (JPA) that is if you want your app to have any back end data base.
• Java itself.
• JSEE while you are at it.
• The Context Dependency Injection specification (CDI) and how it clashes with and is used with JSF 2.0
• JQuery -- I would like to see you get along without it.

Now, once you are done with that you can get on with the proprietary specifications, namely the component libraries and provider libraries you will pick up along the way:

• PrimeFaces (my component library of choice)
• RichFaces
• MyFaces
• ICEFaces
• EclipseLink (my JPA Provider)
• Hibernate
• Weld

And don't forget the container! And all those configuration files:

• GlassFish (2, 3, etc)
• JBoss
• Tomcat

So -- THIS IS MAKING IT EASY? Sure, JSF 2.0 is "easy" as long as all you want to do is the most basic web pages with the simplest interactions.

Simply put, JSF 2.0 is the most complicated and cumbersome mishmash of glued together technologies as exists in the software universe today. And I can't think of anything I would rather use.

1. Inexperienced developers usually will create applications that are painfully slow and code will be really ugly and hard to maintain. Its deceptively simple to start, but actually requires some investment in learning if you want to write good programs.
2. At least at the start you will often "stuck" on some problem and will spend more time reading balusc posts on internet than actually working :) After a while it will be less and less of that, but it still can be annoying.
3. Even more annoying when you find out that the problem is not due to you lack of knowledge/mistake but actually a bug. Mojarra was(is?) quite buggy, and another layer of components adds even more problems. Richfaces was biggest piece of crap software ever written :) Don't know how it is now on version 4. We have Primefaces which is better, but still you will run into bugs or lack of features especially with more exotic components. And now you will need to pay for Primefaces updates. So I would say its buggy but its getting better especially after 2.2 version fixed some problems with spec. Framework getting more mature but still far from perfect (maybe myfaces better?).
4. I don't find it especially flexible. Often if you need something very very customized and there are no components that does that - it will be a bit painful. Again I'm talking from average developer perspective - the one with deadlines, quick reading tutorials, and searching stackoverflow when getting stuck because no time to learn how it really works :) Often some components seems to have "almost" what you need, but not exactly and sometimes you might spend too much time to make it do something you want :) Need to be careful in evaluating if its better to create your own or torture existing component. Actually if you are creating something really unique I would not recommend JSF.

So in short my drawbacks would be: Complexity, Not very smooth development progress, buggy, inflexible.

Of course there are advantages too, but that's not what you asked. Anyway that's my experience with framework others might have different opinions, so best way is to just try it for a while to see if its for you (just something more complex - not naive examples - JSF really shines there:) IMHO best use case for JSF is business applications, like CRMs etc...

"JSF will output View-layer HTML and JavaScript that you cannot control or change without going into Controller code."

Actually JSF gives you the flexibility, you can either use standard/third-party components or create your own which you have full control over what is rendered. It is just one xhtml you need to create your custom components with JSF 2.0.

We developed a sample project with JSF (It was a three week research so we may have lose some things!)

We try to use core jsf, if a component is needed we used PrimeFaces.

The project was a web site with navigation. Each page should be loaded via ajax when the menu is clicked.

The site has two usecases:

1. A page with a grid. The grid is loaded via ajax and should support sort and paging
2. A three step wizard page. Each page has client side validation (for simple validations) and server side ajax base validation (for complex validations). Any server exception ( from service layer) should be displayed on the same page of wizard without navigating to next page.

We found that:

1. You need to use some hacks from omniFaces to make the JSF view state fixed. The JSF state will be corrupted when you include pages via ajax in each other. This seems a bug in JSF and may be fixed on next releases (not in 2.3).
2. The JSF Flow is not working correctly with ajax (or we could not make it work!) We try to use primeface wizard component instead but the client validation seems not supported and mean while it was not standard JSF flow standard.
3. When using some jQuery components like jqGird, and you need to load JSON results, then you are advised to use pure servlet, The JSF will do nothing for you. So if you use these kind of components, your design will not fit in JSF.
4. We try to do some client scripts when ajax complete by ajaxComplete and we found that the PF 4 has implemented its own ajax events. We had some jQuery components and we need to change their code.

If you change the above sample to a non Ajax project ( or at least less ajax project) you will not face lots of above issues.

We summarize our research as:

JSF is not working well in an fully ajax base website.

Of course we find lots of nice features in JSF which may be very helpful in some projects, so consider your project needs.

Please refer to JSF technical documents to review JSF advantages, and in my opinion the biggest advantage of JSF, is the COMPLETE AND HUGE support from @BalusC ;-)