Metacat

/**

 *        Name: DBReader.java

 *     Purpose: A Class that creates an XML text document

 *              from a query to a relational DB containing a DOM representation

 * Institution: National Center for Ecological Analysis and Synthesis

 *   Copyright: 2000

 *     Authors: Matt Jones

 *

 *     Version: '$Id$'

 */

import java.io.*;

import java.net.URL;

import java.net.MalformedURLException;

import java.sql.*;

import java.util.Stack;

public class DBReader {

  static  String 	defaultDB = "jdbc:oracle:thin:@localhost:1521:test";

  private Connection	conn = null;

  static public void main(String[] args) {

     if (args.length < 3)

     {

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

        System.err.println("USAGE: java DBReader " +

                           "<nodeid> <user> <password> [dbstring]");

        return;

     } else {

        try {

          String nodeid = args[0];

          String user     = args[1];

          String password = args[2];

          String dbstring = null;

          if (args.length <= 3) {

            dbstring = defaultDB;

          } else {

            dbstring = args[3];

          }

          DBReader rd = new DBReader(user, password, dbstring);

          String xml = rd.readDocument(nodeid);

          System.out.println(xml);

        } catch (Exception e) {

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

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

          e.printStackTrace(System.err);

        }

     }

  }

  private DBReader( String user, String password, String dbstring)

                  throws IOException,

                         SQLException,

                         ClassNotFoundException

  {

     // Open a connection to the database

     conn = openDBConnection(

                "oracle.jdbc.driver.OracleDriver",

                dbstring, user, password);

  }

  private Connection openDBConnection(String dbDriver, String connection,

                String user, String password)

                throws SQLException, ClassNotFoundException {

     // Load the Oracle JDBC driver

     Class.forName (dbDriver);

     // Connect to the database

     Connection conn = DriverManager.getConnection( connection, user, password);

     return conn;

  }

  public String readDocument(String nodeid) {

    StringBuffer doc = new StringBuffer();

    System.out.println("\nGetting document with nodeid: " + nodeid + "\n");

    BasicElement element = readNodeFromDB(nodeid);

    doc.append(element);

    return (doc.toString());

  }

  /** look up the assigned element id from DB connection */

  private BasicElement readNodeFromDB(String nodeid) {

      long element_id=0;

      long nodeparentid=0;

      String nodetype=null;

      String nodename=null;

      String nodedata=null;

      PreparedStatement pstmt;

      try {

        pstmt =

          conn.prepareStatement("SELECT nodeid,nodeparentid,nodetype,

                  nodename,nodedata FROM xml_nodes WHERE nodeid = ?");

        // Bind the values to the query

        pstmt.setString(1, nodeid);

        pstmt.execute();

        try {

          ResultSet rs = pstmt.getResultSet();

          try {

            boolean tableHasRows = rs.next();

            if (tableHasRows) {

              try {

                element_id = rs.getLong(1);

                nodeparentid = rs.getLong(2);

                nodetype = rs.getString(3);

                nodename = rs.getString(4);

                nodedata = rs.getString(5);

              } catch (SQLException e) {

                System.out.println("Error with getInt: " + e.getMessage());

              }

            }

          } catch (SQLException e) {

            System.out.println("Error with next: " + e.getMessage());

          }

        } catch (SQLException e) {

          System.out.println("Error with getrset: " + e.getMessage());

        }

        pstmt.close();

      } catch (SQLException e) {

        System.out.println("Error getting id: " + e.getMessage());

      }

      if (nodetype.equals("ELEMENT")) {

        BasicElement element =

                 new BasicElement(element_id,nodename,nodeparentid);

        element.appendContent(nodedata);

      }

      // Get a list of child nodes and recursively retrieve them as well

      try {

        pstmt =

          conn.prepareStatement("SELECT nodeid,nodeparentid,nodetype, " +

                                "nodename,nodedata FROM xml_nodes " +

                                "WHERE nodeparentid = ?");

        // Bind the values to the query

        pstmt.setString(1, nodeid);

        pstmt.execute();

        try {

          ResultSet rs = pstmt.getResultSet();

          try {

            boolean tableHasRows = rs.next();

            if (tableHasRows) {

              try {

                element_id = rs.getLong(1);

                nodeparentid = rs.getLong(2);

                nodetype = rs.getString(3);

                nodename = rs.getString(4);

                nodedata = rs.getString(5);

              } catch (SQLException e) {

                System.out.println("Error with getInt: " + e.getMessage());

              }

            }

          } catch (SQLException e) {

            System.out.println("Error with next: " + e.getMessage());

          }

        } catch (SQLException e) {

          System.out.println("Error with getrset: " + e.getMessage());

        }

        pstmt.close();

      } catch (SQLException e) {

        System.out.println("Error getting id: " + e.getMessage());

      }

      return element;

  }

}