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 ?

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.

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?

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.