Custom message with FacesContext.getCurrentInstance().addMessage is not displayed in page (JSF)

Question

Hi!

My page:

...
    <div id="header">
       <!-- content header -->
     </div>
     <div id="content">
       <h:messages />
       <h:ouputText value="#{example.text}" />
     </div>
...

My managedBean:

public class ExampleManagedBean(){
       private String text;


       public String getText(){
           FacesContext.getCurrentInstance().
                   addMessage(null, 
                      new FacesMessage(FacesMessage.SEVERITY_WARN, 
                                       "Warning message...", null));
           return text;
       }

       public void setText(String text){
           this.text = text;
       }
   }

My problem is that the warning message not is rendered in page. Why?

Answer 1

FacesMessage is send to <h:messages/> during validation phase of JSF lifecycle. In your case getter is used to derive bean property value and no validation is going on, so the message is empty.

In theory you can use setter validation, but this is a well known antipattern.

You can do "by hand" validation, but in a different way

 <div id="content">
    <h:messages />
    <h:form>
        <h:outputText value="#{example.text}" />
        <h:commandButton value="Click" action="#{example.action}"/>
    </h:form>
 </div>

and the action method is

public String action(){
   FacesContext.getCurrentInstance().
        addMessage(null,
            new FacesMessage(FacesMessage.SEVERITY_WARN,
                                       "Warning message...", null));
           return null;
}

Much cleaner approach would use built-in or custom validator.

Answer 2

I have two ideas.

First, the message is added in the getText() getter. If h:messages is rendered before h:outputText, then the message might not be there yet when h:messages is rendered.

Second, messages disappear on redirects.