Unique Constraint Validation

Question

I have a JPA Entity, and in this entity I have a field that is Annotated by:

import javax.persistence.*;
....

@Column(nullable=false, unique=true)
private String name;

Then I have a form on a XHTML Page wich the following form:

<h:form>
            <p:panel header="Party Creation">
                <h:panelGrid columns="3" id="regGrid">
                    <h:outputLabel for="name">Name: </h:outputLabel>
                    <p:inputText id="name"  value="#{partyCreationBean.party.name}" />
                    <h:message for="name" />

When the form is submitted, the system will call the following method

private Party createNewParty(PartyDTO party_dto) {
    Party p = new Party(party_dto);
    em.persist(p);
            ....

Everything is working fine. If i try to insert a name that is already present in the database, then i will have an exception on the console (but i will not see anything on the page).

My problem is thet I'd like to show a message on the

        <h:message for="name" />

but i have no idea about how to do. Maybe i can catch the exception but then i don't know how to make the message appear, but also I tought that should be a more elegant way than catch the Exception... Anyway, how shall i do it?!

thankyou very much in advance, Samuele.