5.2.2.2. FieldBridge

Some usecases require more than a simple object to string translation when mapping a property to a Lucene index. To give you the greatest possible flexibility you can also implement a bridge as a FieldBridge. This interface gives you a property value and let you map it the way you want in your Lucene Document.The interface is very similar in its concept to the Hibernate UserType's.

You can for example store a given property in two different document fields:

Example 5.17. Implementing the FieldBridge interface in order to a given property into multiple document fields

/**
 * 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
        Field field = new Field(name + ".year", String.valueOf(year),
            luceneOptions.getStore(), luceneOptions.getIndex(),
            luceneOptions.getTermVector());
        field.setBoost(luceneOptions.getBoost());
        document.add(field);
  
        // set month and pad it if needed
        field = new Field(name + ".month", month < 10 ? "0" : ""
            + String.valueOf(month), luceneOptions.getStore(),
            luceneOptions.getIndex(), luceneOptions.getTermVector());
        field.setBoost(luceneOptions.getBoost());
        document.add(field);
  
        // set day and pad it if needed
        field = new Field(name + ".day", day < 10 ? "0" : ""
            + String.valueOf(day), luceneOptions.getStore(),
            luceneOptions.getIndex(), luceneOptions.getTermVector());
        field.setBoost(luceneOptions.getBoost());
        document.add(field);
    }
}

//property
@FieldBridge(impl = DateSplitBridge.class)
private Date date;