selectItems and enums

[sammy8306]

I can edit a value with an enumerated type in the following way:

<h:selectOneMenu value="#{EditEntryComponent.blogEntry_be.category}">
 <s:selectItems value="#{EditEntryComponent.values}" var="enum" label="#{enum.label}" noSelectionLabel="Please select : " />
 <s:convertEnum />
</h:selectOneMenu>

EditEntryComponent.values points to:

public BlogEntry.Enum_category[] getValues() {
 return BlogEntry.Enum_category.values();
}

However, I would really like to omit this last function, and retrieve the values from the Enum_category enum directly. Does anybody see a way to express this in EL? I see a couple of problems:

* the Java Enum API exposes values(), which does not conform to the get/set convention: not really a problem, I can generate a getValues() static method in each enum declaration which delegates to values()
* I cannot use enhanced EL in s:selectItems (so it appears at least)
* even if I could, how would I make a call to a static method in EL (using possibly a fully qualified type, i.e. some.package.Enum_category.values() )

If someone sees a possibility or clever solution, please let me know...

(one solution I played with is to create the getValues() in the enum as mentioned, and to use an EL expr. like 'EditEntryComponent.blogEntry_be.category.values' in s:selectItems, so we retrieve the possible values from an instance. However, in this case I cannot retrieve the possible values if the instance is null...)

[sammy8306]

Hm, nevermind.... the last solution I sketched, actually works. Even for null values of the enum type. Don't know where I screwed up the initial test of this solution, but it serves me well now. I can generate a selectlist for an enumeration, solely based on the type declaration (ok, given a value of that type actually... without repeating parts of the enum declaration in the xhtml code), which is what I was after.

Maybe it is an idea to incorporate this kind of functionality into s:selectitems (based on the always available values() and name() function on enums)?

[davidfed]

Can you post the code you came up with? I tried some things based on your description but am not succeeding.

[sammy8306]

Here's the code for the enum:

 public enum Enum_level
 {
 GOOD("Good"), AVERAGE("Average"), BAD("Baaad!") ;

 private String label;

 Enum_level (String label)
 {
 this.label = label;
 }

 public String getLabel()
 {
 return label;
 }

 public Enum_level[] getValues() {

 return Enum_level.values();

 }

 public String toString()
 {
 return label;
 }
 }

and here's the accompanying jsf code:

<h:selectOneMenu id="level" value="#{ViewBlogComponent.reply_r.level}">
 <s:selectItems value="#{ViewBlogComponent.reply_r.level.values}" var="enum" label="#{enum.label}" noSelectionLabel="Please select : "/>
 <s:convertEnum/>
 </h:selectOneMenu>

However, it turns out that the problem of not being able to get enum values from non-initialized references is still there. I think the EL-resolver just refuses to call getValues(), when (in this case) getLevel() returns null. Though it can safely do so, since it is a static accessor. Bummer :-( I really hoped this would work... this should be possible, right??

[sammy8306]

Note to self: getValues() of course is not a static method, which explains the failure. I would like to make it static, but if I do it is not recognized as a valid getter method by the EL-resolver. Back to square one (though it is a nice, working solution for non-null enum values).

[davidfed]

Yep, that's what I tried and that's how it didn't work. So I just have an external getter for now.

It looks like Seam 1.3 EL will allow Enum.values() in a value expression. That will simplify this and a number of things like it.

[sammy8306]

Oh, that would be cool, where did you see that?

[davidfed]

It shows up with jboss-el. It was an item in the release notes.

[utdrew]

I have been unable to find any example of using something like #{EnumClass.values()} in the documentation. When I try it seam tries to resolve EnumClass as a managed component and fails. Can anyone help me out here?

<s:selectItems value="#{EnumClass.values()}" />
<s:convertEnum />

I'm using Seam 2.0.0 GA.

[pmuir]

AFAIK this isn't possible, you need to expose your Enum values e.g. via an @Factory

[nicoliniyo]

This worked for me:

...
 @DataModel
 private List<Pais> paisList;

 @Factory("paisList")
 public String listAll() {
 personList= entityManager.createQuery("from Pais").getResultList();
 }
...

xhtml:

...
<h:selectOneMenu value="#{estePais.formaAplicacionRetenciones}">
 <s:convertEnum></s:convertEnum>
 <s:enumItem label="#{m['OPCIONIMPUESTOPORDENTRO']}" enumValue="PORDENTRO"></s:enumItem>
 <s:enumItem label="#{m['OPCIONIMPUESTOPORFUERA']}" enumValue="PORFUERA"></s:enumItem>
 </h:selectOneMenu>

..

Wher Enum Values are: PORDENTRO, PORFUERA
Hope to give u some lights!