Growl

<h:form>
    <p:growl id="growl" showDetail="true" />

    <pm:field>
        <p:outputLabel for="name" value="Name:" /> 
        <p:inputText id="name" value="#{growlView.message}" required="true" label="Name" />
    </pm:field>

    <p:commandButton id="btn" value="Save" actionListener="#{growlView.saveMessage}" update="growl" icon="ui-icon-check"/>
</h:form>
                    

package org.primefaces.showcase.view.message;

import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
import javax.faces.context.FacesContext;

@ManagedBean
public class GrowlView {
    
    private String message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
    
    public void saveMessage() {
        FacesContext context = FacesContext.getCurrentInstance();
        
        context.addMessage(null, new FacesMessage("Successful",  "Your message: " + message) );
        context.addMessage(null, new FacesMessage("Second Message", "Additional Message Detail"));
    }
}