metaqueryhelper.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 java.net.*;
import java.io.*;
import dli2fe.DLI2FEException;

public class MetaQueryHelper {

  Hashtable results = new Hashtable();      // 结果为以文档标志符为key的Hashtable
  public MetaQueryHelper(String queryURL, String query) throws DLI2FEException {
    try {
      System.out.println("MetaQueryHelper:" + query);
      URLConnection con = (new URL(queryURL)).openConnection();
      con.setUseCaches(false);
      con.setDoOutput(true);
      con.setDoInput(true);
      ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
      DataOutputStream out = new DataOutputStream(byteOut);
      out.writeUTF(query);
      out.flush();
      byte buf[] = byteOut.toByteArray();
      con.setRequestProperty("Content-type", "application/octet-stream");
      con.setRequestProperty("Content-length", "" + buf.length);
      DataOutputStream dataOut = new DataOutputStream(con.getOutputStream());
      out.write(buf, 0, buf.length);
      dataOut.write(buf);
      dataOut.flush();
      dataOut.close();

      DataInputStream in = new DataInputStream(con.getInputStream());
      String stringValue = in.readUTF();
      //System.out.println(stringValue);
      in.close();
      analyzeResults(stringValue);
    } catch (IOException ex) {
      new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "MetaQuery service error: " + ex.toString());
    }
  }

  void analyzeResults(String resultStr) throws DLI2FEException {
    try {
      BufferedReader br = new BufferedReader(new StringReader(resultStr));
      String aLine = br.readLine().trim();
      if (!containsOnlyDigits(aLine))
        throw new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "MetaQuery error: " + resultStr);
      int num = Integer.parseInt(aLine);
      for (int i=0; i<num; i++) {
        aLine = br.readLine().trim();
        if (!containsOnlyDigits(aLine))
          throw new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "MetaQuery error: " + resultStr);
        Integer did = new Integer(Integer.parseInt(aLine));
        Vector v = (Vector)results.get(did);
        if (v == null) {
          v = new Vector();
          results.put(did, v);
        }
        int j=0;
        while (br.ready()) {
          br.mark(1);
          if (Character.isDigit((char)br.read())) {
            br.reset();
            char[] bufLen = new char[3];
            br.read(bufLen, 0, 3);
            int len = Integer.parseInt(new String(bufLen));
            char[] bufContent = new char[len];
            br.read(bufContent, 0, len);
            addContent(v, j++, notNull(new String(bufContent)));
          } else {
            br.reset();
            br.readLine();
            break;
          }
        }
      }
    } catch (IOException ex) {
      throw new DLI2FEException(DLI2FEException.SERVER_ERROR_EXC, "MetaQuery error: "+ ex.toString());
    }
  }

  public Set getResultDIDSet() {
    return results.keySet();
  }

  public Vector getResultForDID(int did) {
    return (Vector)results.get(new Integer(did));
  }

  void addContent(Vector v, int index, String content) {
    if (index < v.size()) {
      Vector vi = (Vector)v.elementAt(index);
      if (!content.equals(vi.elementAt(0)))
        vi.add(content);
    } else {
      Vector vi = new Vector();
      vi.add(content);
      v.add(vi);
    }
  }

  String notNull(String inStr) {
    if (inStr == null)
      return "";
    return inStr;
  }

  static boolean containsOnlyDigits(String str) {
    for (int i=0; i<str.length(); i++)
      if (!Character.isDigit(str.charAt(i)))
        return false;
    return true;
  }

  public static void main(String[] args) {
    try {
      MetaQueryHelper mqh = new MetaQueryHelper("http://localhost:8080/SqlSocket/SqlSocket", "select Scene.Name, Scene.Alias, Scene.Location.Province, Scene.Location.DetailLoc, Scene.Introduction, Scene.Level.Class, Scene.Level.Evaluation, Scene.Culture.Figures.Figure, Scene.Poems.Poem, Scene.Culture.OtherCulture, Scene.SubSights.SubSight from Sight"); //"select Scene.Name from Sight where (Scene.Location.Province='河北' or Scene.Location.Province='山西') and Scene.Culture.Figures.Figure='廉颇'");
      Set didSet = mqh.getResultDIDSet();
      Iterator it = didSet.iterator();
      while (it.hasNext()) {
        int i = ((Integer)it.next()).intValue();
        System.out.println(i);
        Vector v = mqh.getResultForDID(i);
        for (int j=0; j<v.size(); j++) {
          Vector vj = (Vector)v.elementAt(j);
          for (int k=0; k<vj.size(); k++)
            System.out.print((String)vj.elementAt(k)+":");
          System.out.print("#");
        }
        System.out.println("");
      }
    } catch (DLI2FEException e) {
      e.printStackTrace();
    }
  }
}