mmquerydecomposer.java

数字图书馆的互操作接口

package dli2fe.helpers;

/**
 * Title:        Digial Library Interoperable Interface Fudan Edition
 * Description:  This project contains all the classes required for DLI2FE interface. Developers use these classes to implement the wrapper and client side codes. The basic functions of DLI2FE is as follows:
 * Search: Search a digital library source site.
 * Metadata: Fetch metadata for a site.
 * ResultAccess: Get results for a given query.
 * DLI2FE uses Dublin Core as the basic attribute model, DAV/DASL as the general XML-based query language and CORBA as distributed object transportation mechanism.
 * Copyright:    Copyright (c) 2001
 * Company:      Fudan University
 * @author Carl Tao
 * @version 1.0
 */
import org.w3c.dom.*;
import dli2fe.xml.XMLObject;
import dli2fe.DLI2FEException;
import dli2fe.xml.DOMUtil;
import dli2fe.sample.MultimediaMeta;
import dli2fe.DAV;

public class MMQueryDecomposer {

  XMLObject metaQuery;
  String image;
  String pfeedback;
  String nfeedback;

  boolean isAnd;

  public MMQueryDecomposer(XMLObject query) throws DLI2FEException {
    metaQuery = query;
    image=null;
    pfeedback=null;
    nfeedback=null;
    isAnd = false;

    Element where = DOMUtil.getChild(query.getElement(), DAV.where);
    if (where == null) {
      throw new DLI2FEException(DLI2FEException.BAD_QUERY_EXC, "No where clause specified: " + query.getString());
    }

    Element firstChildOfWhere = DOMUtil.getChild(where, "*");

    // 如果Where子句的直接儿子是逻辑操作符
    if (firstChildOfWhere != null && (DAV.and.equals(firstChildOfWhere.getLocalName()) || DAV.or.equals(firstChildOfWhere.getLocalName()))) {
      isAnd = DAV.and.equals(firstChildOfWhere.getLocalName());

      Element elMM;                                       // 用来存储多媒体属性的Element
      Element condImage=null, condPFeedback=null, condNFeedback=null;    // 用来存储多媒体条件的Elements
      if ((elMM = DOMUtil.getDescendant((Element)firstChildOfWhere, MultimediaMeta.Namespace, MultimediaMeta.image))!=null) {
        condImage = (Element)elMM.getParentNode().getParentNode();
        image = DOMUtil.getDescendantText(condImage, DAV.literal);
      }
      if ((elMM = DOMUtil.getDescendant((Element)firstChildOfWhere, MultimediaMeta.Namespace, MultimediaMeta.pfeedback))!=null) {
        condPFeedback = (Element)elMM.getParentNode().getParentNode();
        pfeedback = DOMUtil.getDescendantText(condPFeedback, DAV.literal);
      }
      if ((elMM = DOMUtil.getDescendant((Element)firstChildOfWhere, MultimediaMeta.Namespace, MultimediaMeta.nfeedback))!=null) {
        condNFeedback = (Element)elMM.getParentNode().getParentNode();
        nfeedback = DOMUtil.getDescendantText(condNFeedback, DAV.literal);
      }
      // 如果根本没有多媒体查询条件，直接返回
      if (condImage == null)
        return;
      // 如果各个多媒体条件的父节点不同，则查询语句有语法错
      if (condPFeedback != null && condImage.getParentNode() != condPFeedback.getParentNode()
        || condNFeedback != null && condImage.getParentNode() != condNFeedback.getParentNode())
        throw new DLI2FEException(DLI2FEException.BAD_QUERY_EXC, "Unparelleled multimedia conditions: " + query.getString());
      // 删除多媒体查询条件
      Element parentCond = (Element)condImage.getParentNode();
      parentCond.removeChild(condImage);
      if (condPFeedback != null)
        parentCond.removeChild(condPFeedback);
      if (condNFeedback != null)
        parentCond.removeChild(condNFeedback);
      // 向上遍历直到删除所有因删除多媒体条件导致的空节点
      while (DOMUtil.getChild(parentCond, "*") == null && !(DAV.where.equals(parentCond.getLocalName()))) {
        Element oldParent = parentCond;
        parentCond = (Element)oldParent.getParentNode();
        parentCond.removeChild(oldParent);
      }
    // 否则如果Where子句只包含image属性的唯一条件
    } else if (firstChildOfWhere != null && DOMUtil.getDescendant(firstChildOfWhere, MultimediaMeta.Namespace, MultimediaMeta.image)!=null) {
      image = DOMUtil.getDescendantText(firstChildOfWhere, DAV.literal);
      metaQuery = null;
    // 如果Where子句没有条件，产生异常
    } else if (firstChildOfWhere == null)
      throw new DLI2FEException(DLI2FEException.BAD_QUERY_EXC, "Null query: " + query.getString());
  }

  public XMLObject getMetaQuery() {
    return metaQuery;
  }

  public String getQueryImage() {
    return image;
  }

  public String getQueryPFeedback() {
    return pfeedback;
  }

  public String getQueryNFeedback() {
    return nfeedback;
  }

  public boolean isAnd() {
    return isAnd;
  }

  public static void main(String[] args) {
    try {
      //XMLObject xq = new XMLObject("<?xml version=\"1.0\" encoding=\"GB2312\" ?><basicsearch xmlns=\"http://www.cs.fudan.edu.cn/DLI2FE/1.0#\" xmlns:dc=\"http://purl.org/metadata/dublin_core#\" xmlns:mm=\"http://www.cs.fudan.edu.cn/multimedia/#\"> <where>   <like>  <prop><mm:image/></prop>   <literal>file://D:\\Temp\\bookinput.jpg</literal>   </like> </where> </basicsearch>");
      //XMLObject xq = new XMLObject("<?xml version=\"1.0\" encoding=\"GB2312\" ?><basicsearch xmlns=\"http://www.cs.fudan.edu.cn/DLI2FE/1.0#\" xmlns:dc=\"http://purl.org/metadata/dublin_core#\" xmlns:mm=\"http://www.cs.fudan.edu.cn/multimedia/#\"> <where>   <and>  <like>  <prop><mm:image/></prop>   <literal>file://D:\\Temp\\bookinput.jpg</literal>   </like> <eq><prop><mm:pfeedback/></prop><literal>4+5+</literal> </eq><eq><prop><mm:nfeedback/></prop><literal>3+2+</literal> </eq></and></where> </basicsearch>");
      //XMLObject xq = new XMLObject("<?xml version=\"1.0\" encoding=\"GB2312\" ?><basicsearch xmlns=\"http://www.cs.fudan.edu.cn/DLI2FE/1.0#\" xmlns:dc=\"http://purl.org/metadata/dublin_core#\" xmlns:mm=\"http://www.cs.fudan.edu.cn/multimedia/#\"> <where>  <and>  <eq>     <prop><dc:Contributor><dc:Translator/></dc:Contributor></prop> <literal>施伯乐</literal> </eq> <and>  <like>  <prop><mm:image/></prop>   <literal>file://D:\\Temp\\bookinput.jpg</literal>   </like> <eq><prop><mm:pfeedback/></prop><literal>4+5+</literal> </eq><eq><prop><mm:nfeedback/></prop><literal>3+2+</literal> </eq></and></and> </where> </basicsearch>");
      //XMLObject xq = new XMLObject("<?xml version=\"1.0\" encoding=\"GB2312\" ?><basicsearch xmlns=\"http://www.cs.fudan.edu.cn/DLI2FE/1.0#\" xmlns:dc=\"http://purl.org/metadata/dublin_core#\" xmlns:mm=\"http://www.cs.fudan.edu.cn/multimedia/#\"> <where>  <like>  <prop><mm:image/></prop>   <literal>file://D:\\Temp\\bookinput.jpg</literal>   </like>  </where> </basicsearch>");
      XMLObject xq = new XMLObject("<?xml version='1.0' encoding='GB2312' ?><basicsearch xmlns='http://www.cs.fudan.edu.cn/DLI2FE/1.0#' xmlns:mm='http://www.cs.fudan.edu.cn/multimedia/#' xmlns:ts='http://cs.fudan.edu.cn/travel/#'><where><like><prop><mm:image/></prop><literal>http://localhost:8080/multimediasearch/tempsample/first.jpg</literal></like></where></basicsearch>");
      System.out.println(xq.getString());
      MMQueryDecomposer qd = new MMQueryDecomposer(xq);
      if (qd.getMetaQuery() != null)
        System.out.println(qd.getMetaQuery().getString());
      else
        System.out.println(qd.getMetaQuery());
      System.out.println(qd.getQueryImage());
      System.out.println(qd.getQueryPFeedback());
      System.out.println(qd.getQueryNFeedback());
    } catch (DLI2FEException ex) {
      System.out.println(ex);
    }
  }
}