QueryRoute.java

package org.cdlib.xtf.crossQuery;


/*
 * Copyright (c) 2006, Regents of the University of California
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - Neither the name of the University of California nor the names of its
 *   contributors may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
import java.util.HashMap;
import net.sf.saxon.om.NodeInfo;
import org.cdlib.xtf.util.EasyNode;
import org.cdlib.xtf.util.GeneralException;

/**
 * Routes a request to a particular query parser. Optionally contains
 * special tokenizing instructions for one or more URL parameters.
 */
public class QueryRoute 
{
  /** Path to the query parser stylesheet */
  public String queryParserSheet;

  /** Optional: path to the error generator stylesheet */
  public String errorGenSheet;

  /** Special parsing requests for particular URL parameters */
  public HashMap tokenizerMap = new HashMap();

  /** Optional: input to query router stylesheet */
  public String routerInput = null;

  /** Optional: output from query router stylesheet */
  public String routerOutput = null;

  /** Do not construct directly -- use {@link #parse(NodeInfo)} */
  protected QueryRoute() {
  }

  /**
   * Create a default route to the given query parser
   */
  public static QueryRoute createDefault(String queryParserSheet) {
    QueryRoute ret = new QueryRoute();
    ret.queryParserSheet = queryParserSheet;
    return ret;
  } // createDefault()

  /**
   * Reads and parses the route output from a queryRouter stylesheet.
   *
   * @param  input               The output from a queryRouter stylesheet
   * @throws GeneralException    If a read or parse error occurs.
   */
  public static QueryRoute parse(NodeInfo input)
    throws GeneralException 
  {
    // Create the (empty) result
    QueryRoute ret = new QueryRoute();

    // Make sure the root tag is correct.
    EasyNode root = new EasyNode(input);
    String rootTag = root.name();
    if (rootTag.equals("") && root.nChildren() == 1) {
      root = root.child(0);
      rootTag = root.name();
    }

    if (!rootTag.equalsIgnoreCase("route"))
      throw new QueryRouteException(
        "Query router stylesheet must output a 'route' element");

    // Pick out the elements
    for (int i = 0; i < root.nChildren(); i++) 
    {
      EasyNode el = root.child(i);
      if (!el.isElement())
        continue;

      // Was a query parser specified?
      String tagName = el.name();
      if (tagName.equalsIgnoreCase("queryParser"))
        ret.parseQueryParser(el);
      else if (tagName.equalsIgnoreCase("errorGen"))
        ret.parseErrorGen(el);
      else if (tagName.equalsIgnoreCase("tokenize"))
        ret.parseTokenizer(el);
    } // for i

    // Make sure that required parameters were specified.
    if (ret.queryParserSheet == null || ret.queryParserSheet.length() == 0)
      throw new QueryRouteException(
        "Query router stylesheet must output a 'queryParser' element");

    return ret;
  } // parse()

  /**
   * Parse a 'queryParser' element
   */
  private void parseQueryParser(EasyNode el) 
  {
    // Scan each attribute of each element.
    for (int j = 0; j < el.nAttrs(); j++) 
    {
      if (el.attrName(j).equalsIgnoreCase("path"))
        queryParserSheet = el.attrValue(j);
      else {
        throw new GeneralException(
          "Query router attribute " + el.name() + "." + el.attrName(j) +
          " not recognized");
      }
    }
  } // parseQueryParser()

  /**
   * Parse a 'errorGen' element
   */
  private void parseErrorGen(EasyNode el) 
  {
    // Scan each attribute of each element.
    for (int j = 0; j < el.nAttrs(); j++) 
    {
      if (el.attrName(j).equalsIgnoreCase("path"))
        errorGenSheet = el.attrValue(j);
      else {
        throw new GeneralException(
          "Query router attribute " + el.name() + "." + el.attrName(j) +
          " not recognized");
      }
    }
  } // parseErrorGen()

  /**
   * Parse a 'tokenize' element
   */
  private void parseTokenizer(EasyNode el) 
  {
    String paramName = null;
    String tokenizer = null;

    // Scan each attribute of each element.
    for (int j = 0; j < el.nAttrs(); j++) 
    {
      if (el.attrName(j).equalsIgnoreCase("param"))
        paramName = el.attrValue(j);
      else if (el.attrName(j).equalsIgnoreCase("tokenizer"))
        tokenizer = el.attrValue(j);
      else {
        throw new GeneralException(
          "Query router attribute " + el.name() + "." + el.attrName(j) +
          " not recognized");
      }
    }

    // Make sure both specified.
    if (paramName == null || tokenizer == null)
      throw new GeneralException(
        el.name() +
        " element requires 'param' and 'tokenizer' attributes to be specified");

    // Add it.
    tokenizerMap.put(paramName, tokenizer);
  } // parseTokenizer()
} // class QueryRoute