Creating Mappings with Hibernate XML Files - Beginning Hibernate: From Novice to Professional - page 141

Hibernate 3 Type Corresponding Java Type

big_decimal java.math.BigDecimal

big_integer java.math.BigInteger

locale java.util.Locale

timezone java.util.TimeZone

currency java.util.Currency

class java.lang.Class

binary byte[]

text java.lang.String

serializable java.io.Serializable

clob java.sql.Clob

blob java.sql.Blob

In addition to these standard types, you can create your own. Your user type class should
implement either the org.hibernate.usertype.UserType interface or the org.hibernate.
usertype.CompositeUserType interface. Once implemented, a custom type can behave iden-
tically to the standard types; though depending on your requirements, it may be necessary to
specify multiple column names to contain its values, or to provide initialization parameters
for your implementation.
For one-off cases, we recommend that you use components—these have similar behavior,
but they can be “created” in the mapping file without needing to write Hibernate-specific
code. Unless you propose to make substantial use of a custom type throughout your applica-
tion, it will not be worth the effort. We do not discuss this feature further in this topic.

The Anatomy of a Mapping File
A mapping file is a normal XML file. It is validated against a DTD, which can be downloaded
from http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd . You can also look
through the annotated version at http://hibernatebook.com .
The terminology used in the naming of elements and attributes is somewhat confusing at
first because it is the point of contact between the jargon of the object-oriented and relational
worlds.

The <hibernate-mapping> Element
The root element of any mapping file is <hibernate-mapping> . As the top-level element, its
attributes mostly define default behaviors and settings to apply to the child elements (see
Table 7-2).