h:commandbutton vs h:commandlink

Question

We are using JSF-2.1.7 and in all our form post requests. I am trying to justify whether to use or .

Answer 1

In short, my recommendation is a mix of for the primary (default) submit button and s for any additional buttons (e.g. filter, sort, lookup, preview, generate password, ...).

Lengthy explanation follows:

First, some background: One should probably also be aware of the different type attributes. (The type attribute translates directly to the generated attribute.) I haven't found this explicitly stated anywhere, but some tests showed that:

• type="submit" (defaults to this if omitted) does the normal "submit" behaviour of the form (i.e. POSTing the form) as well as the action and/or actionListener.
• type="reset" does the normal "reset" behaviour (i.e. clearing/resetting the form fields) without calling any action and/or actionListeners.
• type="button" generates a button (apparently is a bit more limited than the tag) without calling any action and/or actionListeners.

Apart from resetting the fields, the latter two seem to be useful only to activate e.g. Javascript. They don't POST the form.

So to answer the question: in a form context:

• (which is equivalent to , remember) is often the most useful, especially as most browsers now implement activation of the first submit button found in the DOM tree of the form when Enter is pressed. This might improve your form's user experience

E.g. it is somewhat faster to log with:

1. Username Tab Password Enter

as opposed to

2. Username Tab Password ... move hand from keyboard to mouse, hunt pointer and position on button, click.

Also keep in mind that any buttons (optionally CSS-styled) can still be reached via keyboard by Tabing until the (CSS-styled as a button) has focus, and then Spacebar.

• However, for additional buttons on the form that should do some other action instead of submitting (or "just" clearing the fields), would be more appropriate. This can still be reached via keyboard by Tabing until the (CSS-styled as a button) has focus, and then Enter. Note that this is inconsistent with buttons generated with , which may be CSS-styled to look identical, but are handled differently by the browser (Tab...Spacebar).

That is the general explanation, BUT there are some issues you might want to take note of...

When you do not have a button on a form, only a button (or even no buttons at all), when the user presses Enter the form is still submitted, but without the benefit of a action{Listener} running. Which might not be too big a problem, as the form values get stored in the backing bean and shown again when the page loads, so apart from the server roundtrip the user will often not notice anything is amiss. But that might not be how you want Enter to be handled.... The only way I can think of at the moment circumventing that, is to put an onSubmit event on the form which activates your default button via Javascript.... Arghhhh!!

You should also make sure that your CSS style selectors are sound.

• A.mystyle is applied to ;
• INPUT[type=submit].mystyle to ;
• INPUT[type=reset].mystyle to ;
• INPUT[type=button].mystyle to ;

These can of course be concatenated with a comma as the selector for a single style definition. Or if you want to take the risk of something else being styled as a mystyle button, you could omit the A/INPUT specifiers. However, I have styled my buttons as above, so that I could also use this:

• SPAN.mystyle definition for when the link or button is disabled (e.g. via the disabled attribute) - this allows you to supply a toned-down (greyed) look for a disabled button.

I have also run into some height differences (line height on Button vs. content height on Link - which may be a problem if your button includes a background image as icon instead of text), and also some slight differences in how :before/:after pseudoclasses are handled. All I'm saying: test and retest your CSS on both s and s to make sure they look (essentially) the same!

Here is my summary cheat sheet:

JSF                  
                      type="submit">   type="reset">    type="button">

Translates to        
                      type="submit">   type="reset">    type="button">
Submit form             POST             no, clears flds  no              POST
Javascript events       YES              YES              YES             YES
action{Listener}        YES              no               no              YES
Enter on form activates YES              no               no              no
Tab...+Enter activates  YES(*)           YES              YES             YES
Tab...+Space activates  YES(*)           YES              YES             no
Highlight on Tab-focus:
- Firefox 32            YES              no               no              no
- Chrome 41             YES              YES              YES             YES
- Internet Explorer 11  YES              YES              YES             YES
- Opera 28              YES              YES              YES             no(*)

(*=Opera 28 seems not to allow tabbing (or Alt+Arrow) to  hyperlinks to activate them.)