Creating Mappings with Hibernate XML Files - Beginning Hibernate: From Novice to Professional - page 151

The child elements of the <component> element are as follows:

(meta*,
tuplizer*,
parent?,
(property | many-to-one | one-to-one |
component | dynamic-component | any |
map | set | list | bag |
array | primitive-array)* )

We provide a full example of the use of the <component> element in the “Mapping Compo-
sition” section later in this chapter.

The <one-to-one> Element
The <one-to-one> element expresses the relationship between two classes, where each instance
of the first class is related to a single instance of the second, and vice versa. Such a one-to-one
relationship can be expressed either by giving each of the respective tables the same primary
key values, or by using a foreign key constraint from one table onto a unique identifier column
of the other. Table 7-8 shows the attributes that apply to the <one-to-one> element.

Table 7-8. The <one-to-one> Attributes

Attribute Values Default Description

access

Specifies how the class member should be accessed:
field for direct field access or attribute for access
via the get and set methods.

cascade

Determines how changes to the parent entity will
affect the linked relation.

check The SQL to create a multirow check constraint for

schema generation.

class The property type of the attribute or field (if omit-

ted, this will be determined by reflection).

constrained true , false Indicates that a foreign key constraint on the primary

key of this class references the table of the associated
class.

embed-xml true , false

When using XML relational persistence, indicates
whether the XML tree for the associated entity itself,
or only its identifier, will appear in the generated
XML tree.

entity-name

The entity name of the associated class.

fetch join , select The mode in which the element will be retrieved

( outer join , a series of select s, or a series of subse-
lect s). Only one member of the enclosing class can
be retrieved by outer join .

foreign-key The name to assign to the foreign key enforcing the

relationship.

formula

Allows the value to which the associated class maps
its foreign key to be overridden using an SQL formula.
Continued