AqpFieldMapperProcessor.java

package org.apache.lucene.queryparser.flexible.aqp.processors;

import java.util.List;
import java.util.Map;

import org.apache.lucene.queryparser.flexible.messages.MessageImpl;
import org.apache.lucene.queryparser.flexible.aqp.parser.AqpStandardQueryConfigHandler;
import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.core.config.ConfigurationKey;
import org.apache.lucene.queryparser.flexible.core.config.QueryConfigHandler;
import org.apache.lucene.queryparser.flexible.core.nodes.FieldQueryNode;
import org.apache.lucene.queryparser.flexible.core.nodes.QueryNode;
import org.apache.lucene.queryparser.flexible.core.processors.QueryNodeProcessorImpl;

/**
 * Looks at the QueryNode(s) and translates the field name if we have a mapping
 * for it. It is used to change the field names on-the-fly
 * 
 * @see QueryConfigHandler
 * 
 */
public class AqpFieldMapperProcessor extends QueryNodeProcessorImpl {

  private Map<String, String> fieldMap;
  ConfigurationKey<Map<String, String>> mapKey = AqpStandardQueryConfigHandler.ConfigurationKeys.FIELD_MAPPER;

  public AqpFieldMapperProcessor() {
    // empty constructor
  }

  @Override
  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
    if (getQueryConfigHandler().has(mapKey)) {
      fieldMap = getQueryConfigHandler().get(mapKey);
      if (this.fieldMap != null) {
        return super.process(queryTree);
      }
    }

    return queryTree;
  }

  @Override
  protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {
    if (node instanceof FieldQueryNode) {
      String field = ((FieldQueryNode) node).getFieldAsString();
      if (fieldMap.containsKey(field)) {
        String newField = fieldMap.get(field);
        if (newField == null) {
          throw new QueryNodeException(new MessageImpl("Server error",
              "The configuration error, field " + field
                  + " is translated to: null"));
        }
        ((FieldQueryNode) node).setField(newField);
      }
    }
    return node;
  }

  @Override
  protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {
    return node;
  }

  @Override
  protected List<QueryNode> setChildrenOrder(List<QueryNode> children)
      throws QueryNodeException {
    return children;
  }

}