import org.apache.lucene.queries.function.docvalues.FloatDocValues; //导入依赖的package包/类
@Override
public FunctionValues getValues(Map context, AtomicReaderContext readerContext) throws IOException {
  IndexSearcher searcher = (IndexSearcher)context.get("searcher");
  final TFIDFSimilarity similarity = IDFValueSource.asTFIDF(searcher.getSimilarity(), field);
  if (similarity == null) {
    throw new UnsupportedOperationException("requires a TFIDFSimilarity (such as DefaultSimilarity)");
  }
  final NumericDocValues norms = readerContext.reader().getNormValues(field);

  if (norms == null) {
    return new ConstDoubleDocValues(0.0, this);
  }
  
  return new FloatDocValues(this) {
    @Override
    public float floatVal(int doc) {
      return similarity.decodeNormValue(norms.get(doc));
    }
  };
}
 

import org.apache.lucene.queries.function.docvalues.FloatDocValues; //导入依赖的package包/类
@Override
public FunctionValues getValues(Map context, AtomicReaderContext readerContext) throws IOException {
  IndexSearcher searcher = (IndexSearcher)context.get("searcher");
  final TFIDFSimilarity similarity = IDFValueSource.asTFIDF(searcher.getSimilarity(), field);
  if (similarity == null) {
    throw new UnsupportedOperationException("requires a TFIDFSimilarity (such as DefaultSimilarity)");
  }
  final NumericDocValues norms = readerContext.reader().getNormValues(field);

  if (norms == null) {
    return new ConstDoubleDocValues(0.0, this);
  }
  
  return new FloatDocValues(this) {
    @Override
    public float floatVal(int doc) {
      return similarity.decodeNormValue((byte)norms.get(doc));
    }
  };
}
 

import org.apache.lucene.queries.function.docvalues.FloatDocValues; //导入依赖的package包/类
@Override
public FunctionValues getValues(@SuppressWarnings("rawtypes") Map context, final LeafReaderContext readerContext)
      throws IOException {
   final FunctionValues sourceValues = source.getValues(context, readerContext);

   return new FloatDocValues(this) {
      @Override
      public float floatVal(int doc) throws IOException {
         if (isValidAtomicReaderContext(readerContext)) {
            if (!isCached(doc)) {
               cache.setFloat(doc, sourceValues.floatVal(doc));
            }

            return cache.getFloat(doc);
         }

         return sourceValues.floatVal(doc);
      }
   };
}
 

import org.apache.lucene.queries.function.docvalues.FloatDocValues; //导入依赖的package包/类
public FunctionValues getValues(Map context, LeafReaderContext readerContext) throws IOException {
    final IndexReader ir = readerContext.reader();
    final String indexedField = this.indexedField;

    return new FloatDocValues(this) {
        public float floatVal(int docNum) {
            if(valuesToIntersect.size() == 0){
                return 0;
            }

            HashSet<String> fieldValues = null;
            try {
                final Fields vectors= ir.getTermVectors(docNum);
                if (vectors != null) {
                    if (vectors != null) {
                        Terms vector = vectors.terms(indexedField);
                        if (vector != null) {
                            fieldValues = new HashSet<String>(TermExtractionHelper.getTermsFromTermVectorField(vector));
                        }
                    }
                }  
                if(fieldValues == null){
                    Set<String> fields = new HashSet<String>();
                    fields.add(indexedField);
                    Document d = ir.document(docNum, fields);

                    IndexableField field = d.getField(indexedField);
                    if (field != null) {
                        fieldValues = new HashSet<String>(TermExtractionHelper.getTermsFromField(analyzer, field));
                    }
                }
                if(fieldValues == null || fieldValues.size() == 0){
                    return 0;
                }

                // store field size before modifying set
                int fieldSize = fieldValues.size();
                if(similarity.equals(SimilarityType.JACCARD)){
                    HashSet<String> union = new HashSet<String>(fieldValues);
                    union.addAll(valuesToIntersect);

                    // intersection
                    fieldValues.retainAll(valuesToIntersect);
                    float intersection = fieldValues.size();
                    // no divide by zero as asserted field size is > 0, thus union > 0
                    return intersection / union.size();
                }

                fieldValues.retainAll(valuesToIntersect);
                float intersectionSize = fieldValues.size();
                if(intersectionSize == 0){
                    return 0;
                }

                if(similarity.equals(SimilarityType.DOC_LEN)){
                    return intersectionSize / fieldSize;
                }

                if(similarity.equals(SimilarityType.PARAM_LEN)){
                    return intersectionSize / valuesToIntersect.size();
                }
                else if(similarity.equals(SimilarityType.DICE)) {
                    return (2*intersectionSize) / (fieldSize + valuesToIntersect.size());
                }

                return 0;
            }
            catch(Exception e){
                e.printStackTrace();
            }
            return 0;
        };
    };
}