java/src/main/com/google/appengine/api/search/MatchScorer.java

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.search;
   4
   5 /**
   6  * Assigns a document score based on term frequency.
   7  *
   8  * If you add a MatchScorer to a SortOptions as in the following code:
   9  * <pre>
  10  *  SortOptions sortOptions = SortOptions.newBuilder()
  11  *      .setMatchScorer(MatchScorer().newBuilder())
  12  *      .build();
  13  * </pre>
  14  * then this will sort the documents in descending score order. The scores
  15  * will be positive. If you want to sort in ascending order, then use the
  16  * following code:
  17  * <pre>
  18  *   SortOptions sortOptions = SortOptions.newBuilder()
  19  *       .setMatchScorer(MatchScorer.newBuilder())
  20  *       .addSortExpression(
  21  *           SortExpression.newBuilder()
  22  *               .setExpression(SortExpression.SCORE_FIELD_NAME)
  23  *               .setDirection(SortExpression.SortDirection.ASCENDING)
  24  *               .setDefaultValueNumeric(0.0))
  25  *       .build();
  26  * </pre>
  27  * The scores in this case will be negative.
  28  *
  29  */
  30 public class MatchScorer {
  31
  32   /**
  33    * A builder that constructs {@link MatchScorer MatchScorers}.
  34    * A MatchScorer will invoke a scorer on each search result. The
  35    * following code illustrates building a match scorer to score documents:
  36    * <p>
  37    * <pre>
  38    *   MatchScorer scorer = MatchScorer.newBuilder().build();
  39    * </pre>
  40    */
  41   public static class Builder {
  42
  43     Builder() {
  44     }
  45
  46     /**
  47      * Builds a {@link MatchScorer} from the set values.
  48      *
  49      * @return a {@link MatchScorer} built from the set values
  50      */
  51     public MatchScorer build() {
  52       return new MatchScorer(this);
  53     }
  54   }
  55
  56   /**
  57    * Constructs a text sort specification using the values from the
  58    * {@link Builder}.
  59    */
  60   MatchScorer(Builder builder) {
  61   }
  62
  63   /**
  64    * Copies the contents of the MatchScorer into a scorer
  65    * spec protocol buffer.
  66    *
  67    * @return the protocol buffer builder with the contents of the MatchScorer
  68    * scoring information
  69    */
  70   SearchServicePb.ScorerSpec.Builder copyToScorerSpecProtocolBuffer() {
  71     SearchServicePb.ScorerSpec.Builder builder = SearchServicePb.ScorerSpec.newBuilder();
  72     builder.setScorer(SearchServicePb.ScorerSpec.Scorer.MATCH_SCORER);
  73     return builder;
  74   }
  75
  76   /**
  77    * Creates and returns a MatchScorer Builder.
  78    *
  79    * @return a new {@link MatchScorer.Builder}. Set the parameters for scorer
  80    * on the Builder, and use the {@link Builder#build()} method
  81    * to create a concrete instance of MatchScorer
  82    */
  83   public static Builder newBuilder() {
  84     return new Builder();
  85   }
  86
  87   @Override
  88   public String toString() {
  89     return "MatchScorer()";
  90   }
  91 }