Find component by ID in JSF

问题:

I want to find some UIComponent from managed bean by the id that I have provided.

I have written the following code:

private UIComponent getUIComponent(String id) {  
      return FacesContext.getCurrentInstance().getViewRoot().findComponent(id) ;  
}

I have defined a p:inputTextarea as:

<p:inputTextarea id="activityDescription" value="#{adminController.activityDTO.activityDescription}" required="true" maxlength="120"
    autoResize="true" counter="counter" counterTemplate="{0} characters remaining." cols="80" rows="2" />

Now if a call to the method as getUIComponent("activityDescription") it is returning null, but if I call it as getUIComponent("adminTabView:activityForm:activityDescription") then I can get the org.primefaces.component.inputtextarea.InputTextarea instance.

Is there any way to get the component with only the id i.e., "activityDescription" not the absolute id i.e., "adminTabView:activityForm:activityDescription"?

回答1:

You can use the following code:

public UIComponent findComponent(final String id) {

    FacesContext context = FacesContext.getCurrentInstance(); 
    UIViewRoot root = context.getViewRoot();
    final UIComponent[] found = new UIComponent[1];

    root.visitTree(new FullVisitContext(context), new VisitCallback() {     
        @Override
        public VisitResult visit(VisitContext context, UIComponent component) {
            if(component.getId().equals(id)){
                found[0] = component;
                return VisitResult.COMPLETE;
            }
            return VisitResult.ACCEPT;              
        }
    });

    return found[0];

}

This code will find only the first component in the tree with the id you pass. You will have to do something custom if there are 2 components with the same name in the tree (this is possible if they are under 2 different naming containers).

回答2:

I try this code, and it's help:

private static UIComponent getUIComponentOfId(UIComponent root, String id){
    if(root.getId().equals(id)){
        return root;
    }
    if(root.getChildCount() > 0){
        for(UIComponent subUiComponent : root.getChildren()){
                UIComponent returnComponent = getUIComponentOfId(subUiComponent, id);
                if(returnComponent != null){
                    return returnComponent;
            }
        }
    }
    return null;
}

Thanks

回答3:

Maybe it's not possible. The FacesContext.getCurrentInstance().getViewRoot().findComponent(id) method returns only one UIComponent. The ViewRoot is constructed as a tree so if you have two forms in the view, each one with a component with id="text", they will have it's parent components added to the id so they won't conflict. If you put the two id="text" components within the same form, you will have java.lang.IllegalStateException thrown.

If you want to find all components with the searched id, you could write a method that implements:

List<UIComponent> foundComponents = new ArrayList();
for(UIComponent component: FacesContext.getCurrentInstance().getViewRoot().getChildren()) {
    if(component.getId().contains("activityDescription")){
        foundComponents.add(component);
    }
}

Or if you want to find the first occurrence:

UIComponent foundComponent;
for(UIComponent component: FacesContext.getCurrentInstance().getViewRoot().getChildren()) {
    if(component.getId().contains("activityDescription")){
        foundComponent = component;
        break;
    }
}

回答4:

Just put prependId="false" to your form in which this textarea is.

回答5:

Yes, in all parent components which are NamingContainers you have to add attribute prependId="false" - it will works in <h:form> for sure and should work in others.
If it is not possible to set it via attribute in .xhtml file you have to set such value programaticaly.

Suggestion after question's author comment:

If there is not such attribute in components that you are using try write find method like this:

private UIComponent findComponent(String id, UIComponent where) {
if (where == null) {
   return null;
}
else if (where.getId().equals(id)) {
   return where;
}
else {
   List<UIComponent> childrenList = where.getChildren();
   if (childrenList == null || childrenList.isEmpty()) {
      return null;
   }
   for (UIComponent child : childrenList) {
      UIComponent result = null;
      result = findComponent(id, child);
      if(result != null) {
         return result;
   }
   return null;
}   

Next just invoke

UIComponent iamLookingFor = findComponent(myId, FacesContext.getCurrentInstance().getViewRoot());

That will help?