In JSF what is the shortest way to output List<SomeObj> as comma separated list of "name" properties of SomeObj

Question

I have a question about outputing a list of objects as a comma separated list in JSF.

Let's say:

public class SomeObj {
  private String name;
  ... constructors, getters and setters ...
}

and List<SomeObj>:

List<SomeObj> lst = new ArrayList<SomeObj>();
lst.add(new SomeObj("NameA"));
lst.add(new SomeObj("NameB"));
lst.add(new SomeObj("NameC"));

to output it as a listbox I can use this code:

<h:selectManyListbox id="id1"
                  value="#{listHolder.selectedList}">
  <s:selectItems value="#{listHolder.lst}"
                   var="someObj"
                 label="#{someObj.name}"/>
  <s:convertEntity />
</h:selectManyListbox>

But what is the easiest way to output the list as is, comma seperated ? Like this:

NameA, NameB, NameC

Should I use JSTL <c:forEach/> or may be the <s:selectItems/> tag can also be used ?

Charley

Don't tag jsp if you're using facelets. Those are two entirely distinct view technologies, Facelets being less or more the successor of JSP when talking in JSF context. I've retagged accordingly. – Gladstone

Answer 1

use <ui:repeat> (from facelets). It's similar to c:forEach

Or pre-compute the comma-separated string in the managed bean, and obtain it via a getter.

Anticyclone

I think he's not using Facelets since he explicitly tagged JSP. – Gladstone

sometimes they tag so just because a .jsp extension is used (with facelets inside) :) – Anticyclone

@Vitaly Polonetsky use ui:repeat and use the inner part from BalusC's answer – Anticyclone

Answer 2

Given a List<Person> persons where Person has a name property,

• If you're already on Java EE 7 with EL 3.0, then use EL stream API.

  #{bean.persons.stream().map(p -> p.name).reduce((p1, p2) -> p1 += ', ' += p2).get()}
  

• If you're not on EL 3.0 yet, but have JSF 2.x at hands, then use Facelets <ui:repeat>.

  <ui:repeat value="#{bean.persons}" var="person" varStatus="loop">
      #{person.name}#{not loop.last ? ', ' : ''}
  </ui:repeat>
  

• Or if you're still on jurassic JSP, use JSTL <c:forEach>.

  <c:forEach items="#{bean.persons}" var="person" varStatus="loop">
      ${person.name}${not loop.last ? ', ' : ''}
  </c:forEach>
  

See also:

• How iterate over List<T> and render each item in JSF Facelets
• JSTL in JSF2 Facelets... makes sense?

Gladstone

Am I correct in that this requires JSF 2.0, i.e. varStatus is not supported for JSF 1.2 with facelets? – Limit

@meriton: Yes, you're correct. The c:forEach should however work by xmlns:c="http://java.sun.com/jsp/jstl/core". – Gladstone

Thanks for the confirmation. Being a tag handler, c:forEach won't work for me, since the number of repetitions changes after the view is constructed. But I found another way (which I added as answer). – Limit

@meriton: nice one! Yes, I should have added that JSTL only runs at view build time. – Gladstone

Awesome. A lambda string joiner in one line for JSF EL... As usual, crazy stuff coming from BalusC is rather rare. 😉😉😉 – Gwendolyn

Answer 3

If you can't use varStatus because you're stuck with using JSF 1.2, you can do:

<ui:repeat value="#{listHolder.lst}" var="someObj">#{someObj != listHolder.lst[0] ? ',' : ''}
#{someObj.name}</ui:repeat>

The absence of whitespace around the EL-expressions is deliberate, we don't want a space to appear there in the rendered HTML.

Limit

I think it should be: <ui:repeat value="#{listHolder.lst}" var="someObj">#{someObj != listHolder.lst[listHolder.lst.size()-1] ? ',' : ''} #{someObj.name}</ui:repeat> – Sexton