Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that implements utility methods like:

 *             1/ Reding all doctypes from db connection

 *             2/ Reading Lore type Data Guide from db connection

 *  Copyright: 2000 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Jivka Bojilova

 *    Release: @release@

 * 

 *   '$Author: bojilova $'

 *     '$Date: 2000-08-25 16:18:34 -0700 (Fri, 25 Aug 2000) $'

 * '$Revision: 413 $'

 */

package edu.ucsb.nceas.metacat;

import java.sql.Connection;

import java.sql.SQLException;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.util.Enumeration;

import java.util.Vector;

import java.util.Stack;

/**

 * A suite of utility classes for quering DB

 */

public class DBUtil {

  private Connection	conn = null;

  /**

   * main routine used for testing.

   * <p>

   * Usage: java DBUtil <-dt|-dg>

   *

   * @param -dt for selecting all doctypes

   *        -dg for selecting DataGuide

   */

  static public void main(String[] args) {

     if (args.length < 1)

     {

        System.err.println("Wrong number of arguments!!!");

        System.err.println("USAGE: java DBUtil <-dt | -dg [doctype]>");

        return;

     } else {

        try {

          // Open a connection to the database

          MetaCatUtil   util = new MetaCatUtil();

          Connection dbconn = util.openDBConnection();

          DBUtil dbutil = new DBUtil( dbconn );

          if ( args[0].equals("-dt") ) {

            String doctypes = dbutil.readDoctypes();

            System.out.println(doctypes);

          } else if ( args[0].equals("-dg") ) {

            String doctype = null;

            if ( args.length == 2 ) { doctype = args[1]; }

            String dataguide = dbutil.readDataGuide(doctype);

            System.out.println(dataguide);

          } else {

            System.err.println("USAGE: java DBUtil <-dt | -dg [doctype]>");

          }  

        } catch (Exception e) {

          System.err.println("EXCEPTION HANDLING REQUIRED");

          System.err.println(e.getMessage());

          e.printStackTrace(System.err);

        }

     }

  }

  /**

   * Construct an instance of the utility class

   */

  public DBUtil( Connection conn ) {

    this.conn = conn;

  }

  /**

   * read all doctypes from db connection in XML format

   * select all Public Id from xml_catalog table

   */

  public String readDoctypes()

        throws SQLException  {

    Vector doctypeList = new Vector();

    try {

      PreparedStatement pstmt =

        conn.prepareStatement("SELECT public_id FROM xml_catalog " +

                              "WHERE entry_type = 'DTD'");

      pstmt.execute();

      ResultSet rs = pstmt.getResultSet();

      boolean tableHasRows = rs.next();

      while (tableHasRows) {

           doctypeList.addElement(rs.getString(1));

           tableHasRows = rs.next();

      }

      pstmt.close();

    } catch (SQLException e) {

      System.out.println("DBUtil.readDoctypes(): " + e.getMessage());

      throw e;

    }

    return formatToXML(doctypeList, "doctype");

  }

  /**

   * read Data Guide for a given doctype from db connection in XML format

   * select all distinct absolute paths from xml_index table

   */

  public String readDataGuide( String doctype )

        throws SQLException  {

    Vector dataguide = new Vector();

    String path;

    PreparedStatement pstmt;

    try {

        if ( doctype != null ) {

            pstmt = conn.prepareStatement("SELECT distinct path, nodeid " + 

                                          "FROM xml_index " +

                                          "WHERE path LIKE '/%' " + 

                                          "AND doctype LIKE ? " +

                                          "ORDER BY nodeid");

            pstmt.setString(1, doctype);

        } else {

            pstmt = conn.prepareStatement("SELECT distinct path, doctype, nodeid " + 

                                          "FROM xml_index " +

                                          "WHERE path LIKE '/%' " + 

                                          "ORDER BY doctype, nodeid");

        }

        pstmt.execute();

        ResultSet rs = pstmt.getResultSet();

        boolean tableHasRows = rs.next();

        while (tableHasRows) {

            path = rs.getString(1);

            if ( dataguide.indexOf(path) == -1 ) {

                dataguide.addElement(path);

            }    

            tableHasRows = rs.next();

        }

        pstmt.close();

    } catch (SQLException e) {

      System.out.println("DBUtil.readDataGuide(): " + e.getMessage());

      throw e;

    }

    return formatToXML(dataguide);

  }

  /**

   * format the DataGuide ResultSet to XML

   */

  private String formatToXML(Vector resultset) {

    String currPath = null;

    String currElement = null;

    String prevElement = null;

    StringBuffer result = new StringBuffer();

    Enumeration rs = resultset.elements(); 

    Stack st = new Stack();

    int i = 0;

    result.append("<?xml version=\"1.0\"?>\n");

    result.append("<resultset>\n"); 

    while (rs.hasMoreElements()) {

        currPath = (String)rs.nextElement();

        while ( !In(prevElement, currPath) ) {

            currElement = (String)st.pop();

            result.append(pad(" ",i--) + "</" + currElement + ">\n");

            if ( st.empty() ) 

                prevElement = null;

            else    

                prevElement = (String)st.peek();

        }    

        currElement = getElementFromPath(currPath);

        st.push(currElement);

        result.append(pad(" ",++i) + "<" + currElement + ">\n");

        prevElement = currElement;

    }

    while ( !st.empty() ) {

        prevElement = (String)st.pop();

        result.append(pad(" ",i--) + "</" + prevElement + ">\n");

    }    

    result.append("</resultset>\n"); 

    return result.toString();

  }

  /**

   * check if element is in path like /elem1/elem2/elemn3

   */

  private boolean In(String element, String path) {

    if ( element == null ) return true;

    return ( path.indexOf(element) != -1 );

  }

  /**

   * get last element from path like /elem1/elem2/elemn3

   */

  private String getElementFromPath(String path) {

    return ( path.substring(path.lastIndexOf("/")+1) );

  }

  /**

   * repeates the str n-times

   */

  private String pad(String str, int n) {

    String result = "";

    for ( int i = 0; i < n; i++ )

        result = result.concat(str);

    return result;    

  }

  /**

   * format the ResultSet to XML

   */

  private String formatToXML(Vector resultset, String tag) {

    String val = null;

    StringBuffer result = new StringBuffer();

    Enumeration rs = resultset.elements(); 

    result.append("<?xml version=\"1.0\"?>\n");

    result.append("<resultset>\n"); 

    while (rs.hasMoreElements()) {

        val = (String)rs.nextElement();

        result.append("   <" + tag + ">" + val + "</" + tag + ">\n");

    }

    result.append("</resultset>\n"); 

    return result.toString();

  }

}