4.5.6. Dynamic Analyzer Selection

Procedure 4.3. Configure the @AnalyzerDiscriminator

1. Predefine Dynamic Analyzers

   The @AnalyzerDiscriminator requires that all analyzers that are to be used dynamically are predefined via @AnalyzerDef. The @AnalyzerDiscriminator annotation can then be placed either on the class, or on a specific property of the entity, in order to dynamically select an analyzer. An implementation of the Discriminator interface can be specified using the @AnalyzerDiscriminator impl parameter.

   @Indexed
   @AnalyzerDefs({
     @AnalyzerDef(name = "en",
       tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
       filters = {
         @TokenFilterDef(factory = LowerCaseFilterFactory.class),
         @TokenFilterDef(factory = EnglishPorterFilterFactory.class
         )
       }),
     @AnalyzerDef(name = "de",
       tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
       filters = {
         @TokenFilterDef(factory = LowerCaseFilterFactory.class),
         @TokenFilterDef(factory = GermanStemFilterFactory.class)
       })
   })public class BlogEntry {
   
     @Field
     @AnalyzerDiscriminator(impl = LanguageDiscriminator.class)
     private String language;
     
     @Field
     private String text;
     
     private Set<BlogEntry> references;
     
     // standard getter/setter    
     ...
   }
   

2. Implement the Discriminator Interface

   Implement the getAnalyzerDefinitionName() method, which is called for each field added to the Lucene document. The entity being indexed is also passed to the interface method.
   The value parameter is set if the @AnalyzerDiscriminator is placed on the property level instead of the class level. In this example, the value represents the current value of this property.

   public class LanguageDiscriminator implements Discriminator {
       public String getAnalyzerDefinitionName(Object value, Object entity, String field) {
           if ( value == null || !( entity instanceof Article ) ) {
               return null;
           }
           return (String) value;
       }
   }