resultmerger.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 java.util.*;
import dli2fe.DLI2FEException;
import dli2fe.sample.MultimediaMeta;
import dli2fe.xml.*;
import org.w3c.dom.*;
import dli2fe.DAV;

public class ResultMerger {

  Vector results;         // 每个元素都是Vector, 以存储某个属性可能不止一个的返回值
                          // 元素缺省按照多媒体的返回结果排序，如果没有，按照元数据库结果排序
  XMLObject xmlResults;   // 按照XML组装的结果集
  Vector elements;     // 按照DID组织的Hashtable，每个的值指向结果集中相应的结果文档Element
  int numDocs;


  public ResultMerger(MultimediaMeta container, XMLObject xmlPropList, MMQueryHelper mmqh, MetaQueryHelper mqh) throws DLI2FEException {
    elements = new Vector();
    Vector attrs = analyzePropList(xmlPropList);
    if (mmqh==null && mqh==null)
      throw new DLI2FEException(DLI2FEException.ILLEGAL_METHOD_EXC, "Unknown internal error: null result sets");
    xmlResults = new XMLObject("<SearchResult xmlns='http://www.cs.fudan.edu.cn/DLI2FE/1.0#' xmlns:" +
      MultimediaMeta.shortNamespace + "='" + MultimediaMeta.Namespace + "' xmlns:" + container.getShortMetaNamespace() +
      "='" + container.getMetaNamespace() + "'></SearchResult>");
    Vector result = new Vector();     // 先以一个Vector(同属性重复)的Vector(一个结果文档的多个属性)的Vector(若干返回文档)保存结果
    // 如果多媒体返回结果不为空
    if (mmqh != null) {
      Vector listDID = mmqh.getListDID();
      for (int i=0; i<listDID.size(); i++) {
        int did = ((Integer)listDID.elementAt(i)).intValue();
        Vector metaRes = null;
        if (mqh!=null && (metaRes = mqh.getResultForDID(did)) == null)
          continue;
        Vector oneDoc = new Vector();
        oneDoc.add(new Integer(did));
        result.add(oneDoc);
        int mmOffset = 0;
        for (int j=0; j<attrs.size(); j++) {
          if (((String)attrs.elementAt(j)).startsWith(MultimediaMeta.shortNamespace + ":")) {
            MMQueryHelper mmqh1 = new MMQueryHelper(container.getMMQueryURL());
            mmqh1.getIdmms(did);
            Vector mmIdmms = mmqh1.getResults();
            oneDoc.add(mmIdmms);
            mmOffset = 1;
          } else {
            int realOffset = j - mmOffset;    // real position in the meta result
            if (metaRes == null || metaRes.size()<=realOffset)
              throw new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "Internal error: no meta result generated");
            oneDoc.add(metaRes.elementAt(realOffset));
          }
        }
      }
    // 如果未进行多媒体查询
    } else {
      Iterator it = mqh.getResultDIDSet().iterator();
      while (it.hasNext()) {
        int did = ((Integer)it.next()).intValue();
        Vector metaRes = mqh.getResultForDID(did);
        Vector oneDoc = new Vector();
        oneDoc.add(new Integer(did));
        result.add(oneDoc);
        int mmOffset = 0;
        for (int j=0; j<attrs.size(); j++) {
          if (((String)attrs.elementAt(j)).startsWith(MultimediaMeta.shortNamespace + ":")) {
            MMQueryHelper mmqh1 = new MMQueryHelper(container.getMMQueryURL());
            mmqh1.getIdmms(did);
            Vector mmIdmms = mmqh1.getResults();
            oneDoc.add(mmIdmms);
            mmOffset = 1;
          } else {
            int realOffset = j - mmOffset;    // real position in the meta result
            if (metaRes == null || metaRes.size()<=realOffset)
              throw new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "Internal error: no meta result generated");
            oneDoc.add(metaRes.elementAt(realOffset));
          }
        }
      }
    }
    buildXMLResult(container, attrs, result);
  }

  public XMLObject getXMLResult() {
    return xmlResults;
  }

  public Vector getElementsTable() {
    return elements;
  }

  public int getNumDocs() {
    return numDocs;
  }

  Vector analyzePropList(XMLObject propList) {
    NodeList nodes = propList.getElement().getElementsByTagName("*");
    Vector attrs = new Vector();
    for (int i = 0; i < nodes.getLength(); i++) {
      if ("prop".equals(nodes.item(i).getLocalName()))
        attrs.add(nodes.item(i).getFirstChild().getNodeName());
      else
        attrs.add(nodes.item(i).getNodeName());
    }
    return attrs;
  }

  void buildXMLResult(MultimediaMeta container, Vector vecProp, Vector vecResult) {
    Document doc = xmlResults.getDocument();
    Element searchResult = xmlResults.getElement();
    numDocs = vecResult.size();
    for (int i=0; i<vecResult.size(); i++) {
      Vector vecOneDoc = (Vector)vecResult.elementAt(i);
      Element oneDoc = doc.createElement("doc");
      searchResult.appendChild(oneDoc);
      oneDoc.appendChild(DOMUtil.createTextNode(doc, DAV.Namespace, "DID", ((Integer)vecOneDoc.elementAt(0)).toString()));
      elements.add(oneDoc);
      Element propList = doc.createElement("propList");
      oneDoc.appendChild(propList);
      for (int j=1; j<vecOneDoc.size(); j++) {
        Vector values = (Vector)vecOneDoc.elementAt(j);
        String namespace = null;
        String attrName = (String)vecProp.elementAt(j-1);
        if (attrName.startsWith(container.shortNamespace + ":"))
          namespace = container.Namespace;
        else
          namespace = container.getMetaNamespace();

        for (int k=0; k<values.size(); k++) {
          propList.appendChild(DOMUtil.createTextNode(doc, namespace, attrName, (String)values.elementAt(k)));
        }
      }
    }
  }

}