In some cases it is desirable to map a plain sequence of fields in a database record to more complicated structure of attributes in a Java object, where the target attributes are contained (nested) in other attributes. In brief, you can specify a path to the target attribute as a name of the field in a configuration file, and Castor is able to handle such nested attributes. For example:

      <field name="address.country.code"...>
        <sql name="person_country"/>
      </field>
          

The first case is an attribute of an application type that is a container for some value of a Java type supported by Castor. Usually the application type also has some business methods. Examples are: class Balance that contains a BigDecimal value and has some accounting-specific methods; class CountryCode that contains a String value and has methods validate(), getDisplayName(), etc.; class Signature that contains a byte[] value and has some security-specific methods. In order to use such type with Castor you should provide a pair of methods to get/set the value of the Castor-supported type, e.g. getBigDecimal/setBigDecimal, getCode/setCode, getBytes/setBytes.

Assume that you have the class Address

        public class Address {
            private CountryCode _country;
            private String      _city;
            private String      _street;

            public CountryCode getCountry() {
                return _country;
            }
        
            public void setCountry(CountryCode country) {
                _country = country;
            }
            ...
        }
        

        public class CountryCode {
            private String _code;
            private static String[] _allCodes;
            private static String[] _allDisplayNames;

            public String getCode() {
                return _code;
            }
        
            public void setCode(String code) {
                _code = code;
            }

            public void getDisplayName() {
            ...
        }
        

    <class name="Address"...>
      <field name="country.code"...>
        <sql name="addr_country"/>
      </field>
      ...
    </class>
        

        object.getCountry().setCode(value);
        

        country = new CountryCode();
        country.setCode(value);
        object.setCountry(country);
        

        value = object.getCountry().getCode();
        

The second case is an attribute that is a part of a compound attribute, which contains several database fields. For example, database fields person_country, person_city, person_street of the table PERSON correspond to one compound attribute "address" of the class Person:

        public class Person {
            private String  _firstName;
            private String  _lastName;
            private Address _address;

            public Address getAddress() {
                return _address;
            }
        
            public void setAddress(Address address) {
                _address = address;
            }
            ...
        }
        

    <class name="Person"...>
      <field name="address.country.code"...>
        <sql name="person_country"/>
      </field>
      <field name="address.city"...>
        <sql name="person_city"/>
      </field>
      <field name="address.street"...>
        <sql name="person_street"/>
      </field>
      ...
    </class>