4.2. Property/Field Bridge

In Lucene all index fields have to be represented as Strings. For this reason all entity properties annotated with @Field have to be indexed in a String form. For most of your properties, Hibernate Search does the translation job for you thanks to a built-in set of bridges. In some cases, though you need a more fine grain control over the translation process.

4.2.1. Built-in bridges

Hibernate Search comes bundled with a set of built-in bridges between a Java property type and its full text representation.
null
null elements are not indexed. Lucene does not support null elements and this does not make much sense either.
java.lang.String
String are indexed as is
short, Short, integer, Integer, long, Long, float, Float, double, Double, BigInteger, BigDecimal
Numbers are converted in their String representation. Note that numbers cannot be compared by Lucene (ie used in ranged queries) out of the box: they have to be padded

Note

Using a Range query is debatable and has drawbacks, an alternative approach is to use a Filter query which will filter the result query to the appropriate range.
Hibernate Search will support a padding mechanism
java.util.Date
Dates are stored as yyyyMMddHHmmssSSS in GMT time (200611072203012 for Nov 7th of 2006 4:03PM and 12ms EST). You should not really bother with the internal format. What is important is that when using a DateRange Query, you should know that the dates have to be expressed in GMT time.
Usually, storing the date up to the millisecond is not necessary. @DateBridge defines the appropriate resolution you are willing to store in the index ( @DateBridge(resolution=Resolution.DAY) ). The date pattern will then be truncated accordingly. 
@Entity 
@Indexed
public class Meeting {
    @Field(index=Index.UN_TOKENIZED)
    @DateBridge(resolution=Resolution.MINUTE)
    private Date date;
    ...

Warning

A Date whose resolution is lower than MILLISECOND cannot be a @DocumentId
java.net.URI, java.net.URL
URI and URL are converted to their string representation
java.lang.Class
Class are converted to their fully qualified class name. The thread context classloader is used when the class is rehydrated