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.
