4.6.2. Custom Bridges
Custom bridges are available in situations where built-in bridges, or the bridge's String representation, do not sufficiently address the required property types.
4.6.2.1. FieldBridge
For improved flexibility, a bridge can be implemented as a
FieldBridge
. The FieldBridge
interface provides a property value, which can then be mapped in the Lucene Document
. For example, a property can be stored in two different document fields.
Example 4.13. Implementing the FieldBridge Interface
/** * Store the date in 3 different fields - year, month, day - to ease Range Query per * year, month or day (eg get all the elements of December for the last 5 years). * @author Emmanuel Bernard */ public class DateSplitBridge implements FieldBridge { private final static TimeZone GMT = TimeZone.getTimeZone("GMT"); public void set(String name, Object value, Document document, LuceneOptions luceneOptions) { Date date = (Date) value; Calendar cal = GregorianCalendar.getInstance(GMT); cal.setTime(date); int year = cal.get(Calendar.YEAR); int month = cal.get(Calendar.MONTH) + 1; int day = cal.get(Calendar.DAY_OF_MONTH); // set year luceneOptions.addFieldToDocument( name + ".year", String.valueOf( year ), document ); // set month and pad it if needed luceneOptions.addFieldToDocument( name + ".month", month < 10 ? "0" : "" + String.valueOf( month ), document ); // set day and pad it if needed luceneOptions.addFieldToDocument( name + ".day", day < 10 ? "0" : "" + String.valueOf( day ), document ); } } //property @FieldBridge(impl = DateSplitBridge.class) private Date date;
In the following example, the fields are not added directly to the
Lucene Document
. Instead the addition is delegated to the LuceneOptions
helper. The helper will apply the options selected on @Field
, such as Store
or TermVector
, or apply the chosen @Boost
value.
It is recommended that
LuceneOptions
is delegated to add fields to the Document
, however the Document
can also be edited directly, ignoring the LuceneOptions
.
Note
LuceneOptions
shields the application from changes in Lucene API
and simplifies the code.