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4.6. Bridges

When mapping entities, Lucene represents all index fields as strings. All entity properties annotated with @Field are converted to strings to be indexed. Built-in bridges automatically translates properties for the Lucene-based Query API. The bridges can be customized to gain control over the translation process.
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4.6.1. Built-in Bridges
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The Lucene-based Query API includes a set of built-in bridges between a Java property type and its full text representation.
null
Per default null elements are not indexed. Lucene does not support null elements. However, in some situation it can be useful to insert a custom token representing the null value. See Section 4.1.2, “@Field” for more information.
java.lang.String
Strings are indexed, as are:
  • short, Short
  • integer, Integer
  • long, Long
  • float, Float
  • double, Double
  • BigInteger
  • BigDecimal
Numbers are converted into their string representation. Note that numbers cannot be compared by Lucene, or used in ranged queries out of the box, and must be padded

Note

Using a Range query has disadvantages. An alternative approach is to use a Filter query which will filter the result query to the appropriate range.
The Query Module supports using a custom StringBridge. See Section 4.6.2, “Custom Bridges”.
java.util.Date
Dates are stored as yyyyMMddHHmmssSSS in GMT time (200611072203012 for Nov 7th of 2006 4:03PM and 12ms EST). When using a TermRangeQuery, dates are expressed in GMT.
@DateBridge defines the appropriate resolution to store in the index, for example: @DateBridge(resolution=Resolution.DAY). The date pattern will then be truncated accordingly. 
@Indexed
public class Meeting {
    @Field(analyze=Analyze.NO)
    @DateBridge(resolution=Resolution.MINUTE)
    private Date date;
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The default Date bridge uses Lucene's DateTools to convert from and to String. All dates are expressed in GMT time. Implement a custom date bridge in order to store dates in a fixed time zone.
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
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4.6.2. Custom Bridges
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Custom bridges are available in situations where built-in bridges, or the bridge's String representation, do not sufficiently address the required property types.
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4.6.2.1. FieldBridge
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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

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;
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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.
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4.6.2.2. StringBridge
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Use the org.infinispan.query.bridge.StringBridge interface to provide the Lucene-based Query API with an implementation of the expected Object to String bridge, or StringBridge. All implementations are used concurrently, and therefore must be thread-safe.

Example 4.14. Custom StringBridge implementation

/**
 * Padding Integer bridge.
 * All numbers will be padded with 0 to match 5 digits
 *
 * @author Emmanuel Bernard
 */
public class PaddedIntegerBridge implements StringBridge {

    private int PADDING = 5;

    public String objectToString(Object object) {
        String rawInteger = ( (Integer) object ).toString();
        if (rawInteger.length() > PADDING) 
            throw new IllegalArgumentException( "Try to pad on a number too big" );
        StringBuilder paddedInteger = new StringBuilder( );
        for ( int padIndex = rawInteger.length() ; padIndex < PADDING ; padIndex++ ) {
            paddedInteger.append('0');
        }
        return paddedInteger.append( rawInteger ).toString();
    }
}
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The @FieldBridge annotation allows any property or field in the provided example to use the bridge: 
@FieldBridge(impl = PaddedIntegerBridge.class)
private Integer length;
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4.6.2.3. Two-Way Bridge
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A TwoWayStringBridge is an extended version of a StringBridge, which can be used when the bridge implementation is used on an ID property. The Lucene-based Query API reads the string representation of the identifier and uses it to generate an object. The @FieldBridge annotation is used in the same way.

Example 4.15. Implementing a TwoWayStringBridge for ID Properties

public class PaddedIntegerBridge implements TwoWayStringBridge, ParameterizedBridge {

    public static String PADDING_PROPERTY = "padding";
    private int padding = 5; //default

    public void setParameterValues(Map parameters) {
        Object padding = parameters.get( PADDING_PROPERTY );
        if (padding != null) this.padding = (Integer) padding;
    }

    public String objectToString(Object object) {
        String rawInteger = ( (Integer) object ).toString();
        if (rawInteger.length() > padding) 
            throw new IllegalArgumentException( "Try to pad on a number too big" );
        StringBuilder paddedInteger = new StringBuilder( );
        for ( int padIndex = rawInteger.length() ; padIndex < padding ; padIndex++ ) {
            paddedInteger.append('0');
        }
        return paddedInteger.append( rawInteger ).toString();
    }

    public Object stringToObject(String stringValue) {
        return new Integer(stringValue);
    }
}


@FieldBridge(impl = PaddedIntegerBridge.class,
             params = @Parameter(name="padding", value="10") 
private Integer id;
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Important

The two-way process must be idempotent (ie object = stringToObject( objectToString( object ) ) ).
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4.6.2.4. Parameterized Bridge
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A ParameterizedBridge interface passes parameters to the bridge implementation, making it more flexible. The ParameterizedBridge interface can be implemented by StringBridge, TwoWayStringBridge, FieldBridge implementations. All implementations must be thread-safe.
The following example implements a ParameterizedBridge interface, with parameters passed through the @FieldBridge annotation.

Example 4.16. Configure the ParameterizedBridge Interface

public class PaddedIntegerBridge implements StringBridge, ParameterizedBridge {

    public static String PADDING_PROPERTY = "padding";
    private int padding = 5; //default

    public void setParameterValues(Map<String,String> parameters) {
        String padding = parameters.get( PADDING_PROPERTY );
        if (padding != null) this.padding = Integer.parseInt( padding );
    }

    public String objectToString(Object object) {
        String rawInteger = ( (Integer) object ).toString();
        if (rawInteger.length() > padding) 
            throw new IllegalArgumentException( "Try to pad on a number too big" );
        StringBuilder paddedInteger = new StringBuilder( );
        for ( int padIndex = rawInteger.length() ; padIndex < padding ; padIndex++ ) {
            paddedInteger.append('0');
        }
        return paddedInteger.append( rawInteger ).toString();
    }
}


//property
@FieldBridge(impl = PaddedIntegerBridge.class,
             params = @Parameter(name="padding", value="10")
            )
private Integer length;
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4.6.2.5. Type Aware Bridge
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Any bridge implementing AppliedOnTypeAwareBridge will get the type the bridge is applied on injected. For example:
  • the return type of the property for field/getter-level bridges.
  • the class type for class-level bridges.
The type injected does not have any specific thread-safety requirements.
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4.6.2.6. ClassBridge
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More than one property of an entity can be combined and indexed in a specific way to the Lucene index using the @ClassBridge annotation. @ClassBridge can be defined at class level, and supports the termVector attribute.
In the following example, the custom FieldBridge implementation receives the entity instance as the value parameter, rather than a particular property. The particular CatFieldsClassBridge is applied to the department instance.The FieldBridge then concatenates both branch and network, and indexes the concatenation.

Example 4.17. Implementing a ClassBridge

@Indexed
@ClassBridge(name="branchnetwork",
             store=Store.YES,
             impl = CatFieldsClassBridge.class,
             params = @Parameter( name="sepChar", value="" ) )
public class Department {
    private int id;
    private String network;
    private String branchHead;
    private String branch;
    private Integer maxEmployees
}

public class CatFieldsClassBridge implements FieldBridge, ParameterizedBridge {
    private String sepChar;

    public void setParameterValues(Map parameters) {
        this.sepChar = (String) parameters.get( "sepChar" );
    }

    public void set( String name, Object value, Document document, LuceneOptions luceneOptions) {
       
        Department dep = (Department) value;
        String fieldValue1 = dep.getBranch();
        if ( fieldValue1 == null ) {
            fieldValue1 = "";
        }
        String fieldValue2 = dep.getNetwork();
        if ( fieldValue2 == null ) {
            fieldValue2 = "";
        }
        String fieldValue = fieldValue1 + sepChar + fieldValue2;
        Field field = new Field( name, fieldValue, luceneOptions.getStore(),
            luceneOptions.getIndex(), luceneOptions.getTermVector() );
        field.setBoost( luceneOptions.getBoost() );
        document.add( field );
   }
}
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