Untitled

message = new FacesMessage("test<br/>test");

#messages td { white-space: pre; }

<ul>
    <ui:repeat value="#{facesContext.messageList}" var="facesMessage">
        <li>
            <h:outputText value="#{facesMessage.summary}" escape="false" />
        </li>
    </ui:repeat>
</ul>

<o:messages escape="false" />

<p:messages escape="false"/>

StringBuilder sb = new StringBuilder("<html><body>");
sb.append("<p>A list of messages are:</p>");
for(String str : listMessages){
      sb.append("Message: ").append(str).append("<br/>");
}
sb.append("</body></html>");

FacesMessage message = new FacesMessage(sb.toString());
message.setSeverity(FacesMessage.SEVERITY_INFO);
FacesContext.getCurrentInstance().addMessage("", message);