Generated column and table names in hibernate with underscore

how do I force hibernate to generate db schema such that it converts CamelCase into Underscores (using HBM)? Eg. I have:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "开发者_如何学JAVA-//Hibernate/Hibernate Mapping DTD//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cz.csas.pdb.be.model.product.passive">

    <class name="foo.BarBaz">

        <id name="barBazId">
            <generator class="sequence"/>
        </id>

        <property name="extractContactType"/>
        <!-- ... -->
    </class>
</hibernate-mapping>

And I want hibernate to create table like this (oracle):

CREATE TABLE "BAR_BAZ"
  (
    "BAR_BAZ_ID"               NUMBER(19,0) NOT NULL ENABLE,
    "EXTRACT_CONTACT_TYPE"     VARCHAR2(512 CHAR),
    -- PK etc...
  )

I know I can use table/column name in the hbm.xml file, but I want to set it globally (both to save time and prevent errors).

ImprovedNamingStrategy should do exactly what you want. See 3.6. Implementing a NamingStrategy.

In JPA 2 (Hibernate 4), it is even more easier, just add:

<property name="hibernate.ejb.naming_strategy"
         value="org.hibernate.cfg.ImprovedNamingStrategy" />

to your persistence.xml.