Get the validation message for a specific component

Answer 1

The problem you will have with what you're planning is that a single component can have more than one message queued. What are you going to do then? For demonstration purposes, you can use

<h:inputText id="myInputText"
             title="#{facesContext.getMessageList('myInputText').get(0)}"
             style="#{component.valid ? '' : 'border-color:red'}"
             validator="#{MyBean.validate}"
             required="true"
             requiredMessage="required"
             value="#{MyBean.value}" />

EDIT : You should just move the logic into your backing bean:

1. Implement a method that'll pull the detail from an available FacesMessage list, given a clientId

   public String getComponentMessageDetail(String clientId) {
       String detail = null;
       FacesContext ctxt = FacesContext.getCurrentInstance();
       List<FacesMessage> componentMessages = ctxt.getMessages(clientId);
   
       if (componentMessages != null && componentMessages.isEmpty() == false) {
           //returns the detail, from only the first message!
           detail = componentMessages.get(0).getDetail();
       }
   
       return detail;
   }
   

2. Use the utility method in your view

    <h:inputText id="myInputText"
                 title="#{MyBean.getComponentMessageDetail('myInputText')}"
                 style="#{component.valid ? '' : 'border-color:red'}"
                 validator="#{MyBean.validate}"
                 required="true"
                 requiredMessage="required"
                 value="#{MyBean.value}" />
   

Answer 2

How about this java method

public String getComponentMessageDetail(String cid){
  FacesContext ctxt  =  FacesContext.getCurrentInstance();
  Iterator<FacesMessage> cm = ctxt.getMessages(cid);
  List<String> msg = new ArrayList<>();
  while(cm.hasNext()) {
    msg.add(cm.next().getDetail());
  }
  return String.join(" | ", msg);
}

to show everything what's in the message cache?

Also in xhtml

<h:inputText id="myInputText" title="#{MyBean.getComponentMessageDetail('yourFormId:myInputText'}" style="#{component.valid? '' : 'border-color:red'}" validator="#{MyBean.validate}" required="true" requiredMessage="required" value="#{MyBean.value} />

it might be useful to put the name of your form-id in front of the input control's id. Otherwise the message list might have zero items, although there are some.

Here is another way to quickly show validation messages: h:messages