Query data structure 

The engine takes a query in the form of a JSON structure to output prediction.

The JSON input structure is like the following code snippet for our Recommendation Engine example:

    {
      "userEntityId": "u1",
      "number": 10,
      "categories": ["c4", "c3"]
    }

The query JSON structure is mapped via the Query class. The following piece of code shows the example of the Query Class for this engine:

   org.template.recommendation;

    import java.io.Serializable;
    import java.util.Collections;
    import java.util.Set;

    public class Query implements Serializable {
      private final String userEntityId;
      private final int number;
      private final Set<String> categories;
      private final Set<String> whitelist;
      private final Set<String> blacklist;

      public Query(String userEntityId, int number,
        Set<String> categories, Set<String> whitelist,
        Set<String> blacklist) {
          this.userEntityId = userEntityId;
          this.number = number;
          this.categories = categories;
          this.whitelist = whitelist;
          this.blacklist = blacklist;
      }

      public String getUserEntityId() {
        return userEntityId;
      }

      public int getNumber() {
        return number;
      }

      public Set<String> getCategories() {
        if (categories == null) return Collections.emptySet();
        return categories;
      }

      public Set<String> getWhitelist() {
        if (whitelist == null) return Collections.emptySet();
        return whitelist;
      }

      public Set<String> getBlacklist() {
        if (blacklist == null) return Collections.emptySet();
        return blacklist;
      }

      @Override
      public String toString() {
        return "Query{" +
        "userEntityId='" + userEntityId + ''' +
        ", number=" + number +
        ", categories=" + categories +
        ", whitelist=" + whitelist +
        ", blacklist=" + blacklist +
        '}';
      }
    }

Note how the data structure of JSON for query is simply mapped to a class structure.