如何在f中使用枚举值：selectItem（s） [英] How to use enum values in f:selectItem(s)

问题描述

我想做一个selectOneMenu下拉列表，所以我可以选择我的问题的状态。是否可以使f：selectItem更灵活，考虑到枚举的顺序如何变化会发生什么，如果列表很大？我能做得更好吗是否可以自动选择该问题的项目？

枚举类

  public enum Status {
 SUBMITTED，
 REJECTED，
 APPROVED 
} 
  

问题实体

  @Enumerated（EnumType.STRING）
 private状态; 
  

JSF

 < div class =field> 
< h：outputLabel for =questionStatusvalue =Status/> 
< h：selectOneMenu id =questionStatusvalue =＃{bean.question.status}> 
< f：selectItem itemLabel =已提交itemValue =0/> 
< f：selectItem itemLabel =被拒绝itemValue =1/> 
< f：selectItem itemLabel =已批准itemValue =2/> 
< / h：selectOneMenu> 
< hr /> 
< / div> 
  

解决方案

内置转换器为枚举，所以应该这样做：

  @ManagedBean 
 @ApplicationScoped 
 public class Data {
 
 public Status [] getStatuses（）{
 return Status.values（）; 
} 
 
} 
  

with

 < h：selectOneMenu value =＃{bean.question.status}> 
< f：selectItems value =＃{data.statuses}/> 
< / h：selectOneMenu> 
  

（注意：由于JSF 2.0不再需要提供 SelectItem [] 或列表< SelectItem> ， T [] 和列表< T> 也被接受，您可以通过 var 属性访问当前项目

如果您碰巧使用JSF实用程序库 OmniFaces ，那么您可以使用<一个href =http://showcase.omnifaces.org/taghandlers/importConstants =noreferrer> < o：importConstants> 而不是bean。

 < o：importConstants type =com.example.Status/> 
 
< h：selectOneMenu value =＃{bean.question.status}> 
< f：selectItems value =＃{Status}/> 
< / h：selectOneMenu> 
  

如果您打算控制标签，可以将它们添加到状态枚举：

  public enum Status {
 
提交（已提交），
 REJECTED（被拒绝），
已批准（已批准）; 
 
 private String label; 
 
私人状态（String label）{
 this.label = label; 
} 
 
 public String getLabel（）{
 return label; 
} 
 
} 
  

with

 < f：selectItems value =＃{data.statuses}var =status
 itemValue =＃{status}itemLabel =＃{status.label}/>或者更好的是，使枚举值成为本地化资源束的属性键（需要EL 3.0） ：
 < f：selectItems value =＃{data.statuses}var =状态
 itemValue =＃{status}itemLabel =＃{text ['data.status。'+ = status]}/> 
  
在与资源束相关联的属性文件中＃{text}  
  data.status.SUBMITTED =提交
数据。 status.REJECTED =被拒绝
 data.status.APPROVED =已核准
  
 
I want to make a selectOneMenu dropdown so I can select a status on my question. Is it possible to make the f:selectItem more flexible considering what happens if the order of the enums changes, and if the list was large? And could I do this better? And is it possible to automatically "select" the item that the question have?

Enum class
public enum Status {
    SUBMITTED,
    REJECTED,
    APPROVED
}
Question entity
@Enumerated(EnumType.STRING)
private Status status;
JSF
<div class="field">
    <h:outputLabel for="questionStatus" value="Status" />
    <h:selectOneMenu id="questionStatus" value="#{bean.question.status}" >
        <f:selectItem itemLabel="Submitted" itemValue="0" />
        <f:selectItem itemLabel="Rejected" itemValue="1" />
        <f:selectItem itemLabel="Approved" itemValue="2" />
    </h:selectOneMenu>
    <hr />
</div>



解决方案
JSF has a builtin converter for enum, so this should do:
@ManagedBean
@ApplicationScoped
public class Data {

    public Status[] getStatuses() {
        return Status.values();
    }

}
with
<h:selectOneMenu value="#{bean.question.status}" >
    <f:selectItems value="#{data.statuses}" />
</h:selectOneMenu>
(note: since JSF 2.0 there's no need anymore to provide a SelectItem[] or List<SelectItem>, a T[] and List<T> are accepted as well and you can access the current item by var attribute)

If you happen to use JSF utility library OmniFaces, then you could use <o:importConstants> instead of a bean.
<o:importConstants type="com.example.Status" />

<h:selectOneMenu value="#{bean.question.status}" >
    <f:selectItems value="#{Status}" />
</h:selectOneMenu>
If you intend to control the labels as well, you could add them to the Status enum:
public enum Status {

    SUBMITTED("Submitted"),
    REJECTED("Rejected"),
    APPROVED("Approved");

    private String label;

    private Status(String label) {
        this.label = label;
    }

    public String getLabel() {
        return label;
    }

}
with
<f:selectItems value="#{data.statuses}" var="status"
    itemValue="#{status}" itemLabel="#{status.label}" />
Or, better, make the enum value a property key of a localized resource bundle (EL 3.0 required):
<f:selectItems value="#{data.statuses}" var="status"
    itemValue="#{status}" itemLabel="#{text['data.status.' += status]}" />
with this in a properties file associated with resource bundle #{text}
data.status.SUBMITTED = Submitted
data.status.REJECTED = Rejected
data.status.APPROVED = Approved


                        
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