Lucene example source code file (QueryTreeBuilder.java)

This example Lucene source code file (QueryTreeBuilder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

class, deprecated, fieldablenode, hashmap, hashmap, object, querybuilder, querybuilder, querynode, querynode, querynodeexception, querynodeexception, querytreebuilder, string, util

The Lucene QueryTreeBuilder.java source code

package org.apache.lucene.queryParser.core.builders;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.HashMap;
import java.util.List;

import org.apache.lucene.messages.MessageImpl;
import org.apache.lucene.queryParser.core.QueryNodeException;
import org.apache.lucene.queryParser.core.messages.QueryParserMessages;
import org.apache.lucene.queryParser.core.nodes.FieldableNode;
import org.apache.lucene.queryParser.core.nodes.QueryNode;
import org.apache.lucene.queryParser.core.util.StringUtils;
import org.apache.lucene.queryParser.standard.parser.EscapeQuerySyntaxImpl;

/**
 * This class should be used when there is a builder for each type of node.
 * 
 * The type of node may be defined in 2 different ways: - by the field name,
 * when the node implements the {@link FieldableNode} interface - by its class,
 * it keeps checking the class and all the interfaces and classes this class
 * implements/extends until it finds a builder for that class/interface
 * 
 * This class always check if there is a builder for the field name before it
 * checks for the node class. So, field name builders have precedence over class
 * builders.
 * 
 * When a builder is found for a node, it's called and the node is passed to the
 * builder. If the returned built object is not <code>null, it's tagged
 * on the node using the tag {@link QueryTreeBuilder#QUERY_TREE_BUILDER_TAGID}.
 * 
 * The children are usually built before the parent node. However, if a builder
 * associated to a node is an instance of {@link QueryTreeBuilder}, the node is
 * delegated to this builder and it's responsible to build the node and its
 * children.
 * 
 * @see QueryBuilder
 */
public class QueryTreeBuilder implements QueryBuilder {

  /**
   * This tag is used to tag the nodes in a query tree with the built objects
   * produced from their own associated builder.
   */
  public static final String QUERY_TREE_BUILDER_TAGID = QueryTreeBuilder.class
      .getName();

  private HashMap<Class queryNodeBuilders;

  private HashMap<String, QueryBuilder> fieldNameBuilders;

  /**
   * {@link QueryTreeBuilder} constructor.
   */
  public QueryTreeBuilder() {
    // empty constructor
  }

  /**
   * Associates a field name with a builder.
   * 
   * @param fieldName the field name
   * @param builder the builder to be associated
   */
  public void setBuilder(String fieldName, QueryBuilder builder) {

    if (this.fieldNameBuilders == null) {
      this.fieldNameBuilders = new HashMap<String, QueryBuilder>();
    }

    this.fieldNameBuilders.put(fieldName.toString(), builder);

  }

  /**
   * Associates a field name with a builder.
   * 
   * @param fieldName the field name
   * @param builder the builder to be associated
   * 
   * @deprecated use {@link #setBuilder(String, QueryBuilder)} instead
   */
  @Deprecated
  public void setBuilder(CharSequence fieldName, QueryBuilder builder) {
    setBuilder(StringUtils.toString(fieldName), builder);
  }

  /**
   * Associates a class with a builder
   * 
   * @param queryNodeClass the class
   * @param builder the builder to be associated
   */
  public void setBuilder(Class<? extends QueryNode> queryNodeClass,
      QueryBuilder builder) {

    if (this.queryNodeBuilders == null) {
      this.queryNodeBuilders = new HashMap<Class();
    }

    this.queryNodeBuilders.put(queryNodeClass, builder);

  }

  private void process(QueryNode node) throws QueryNodeException {

    if (node != null) {
      QueryBuilder builder = getBuilder(node);

      if (!(builder instanceof QueryTreeBuilder)) {
        List<QueryNode> children = node.getChildren();

        if (children != null) {

          for (QueryNode child : children) {
            process(child);
          }

        }

      }

      processNode(node, builder);

    }

  }

  private QueryBuilder getBuilder(QueryNode node) {
    QueryBuilder builder = null;

    if (this.fieldNameBuilders != null && node instanceof FieldableNode) {
      builder = this.fieldNameBuilders.get(StringUtils
          .toString(((FieldableNode) node).getField()));
    }

    if (builder == null && this.queryNodeBuilders != null) {

      Class<?> clazz = node.getClass();

      do {
        builder = getQueryBuilder(clazz);

        if (builder == null) {
          Class<?>[] classes = node.getClass().getInterfaces();

          for (Class<?> actualClass : classes) {
            builder = getQueryBuilder(actualClass);

            if (builder != null) {
              break;
            }

          }

        }

      } while (builder == null && (clazz = clazz.getSuperclass()) != null);

    }

    return builder;

  }

  private void processNode(QueryNode node, QueryBuilder builder)
      throws QueryNodeException {

    if (builder == null) {

      throw new QueryNodeException(new MessageImpl(
          QueryParserMessages.LUCENE_QUERY_CONVERSION_ERROR, node
              .toQueryString(new EscapeQuerySyntaxImpl()), node.getClass()
              .getName()));

    }

    Object obj = builder.build(node);

    if (obj != null) {
      node.setTag(QUERY_TREE_BUILDER_TAGID, obj);
    }

  }

  private QueryBuilder getQueryBuilder(Class<?> clazz) {

    if (QueryNode.class.isAssignableFrom(clazz)) {
      return this.queryNodeBuilders.get(clazz);
    }

    return null;

  }

  /**
   * Builds some kind of object from a query tree. Each node in the query tree
   * is built using an specific builder associated to it.
   * 
   * @param queryNode the query tree root node
   * 
   * @return the built object
   * 
   * @throws QueryNodeException if some node builder throws a
   *         {@link QueryNodeException} or if there is a node which had no
   *         builder associated to it
   */
  public Object build(QueryNode queryNode) throws QueryNodeException {
    process(queryNode);

    return queryNode.getTag(QUERY_TREE_BUILDER_TAGID);

  }

}