Metacat

/**

 *        Name: ReaderElement.java

 *     Purpose: A Class that represents an XML element and its contents,

 *              and can build itself from a database connection

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

 *              National Center for Ecological Analysis and Synthesis

 *     Authors: Matt Jones

 *

 *     Version: '$Id: ReaderElement.java 51 2000-04-17 23:06:07Z jones $'

 */

package edu.ucsb.nceas.metacat;

import java.sql.*;

import java.io.IOException;

import java.util.Vector;

import java.util.Enumeration;

/**

 * A Class that represents an XML element and its contents,

 * and can build itself from a database connection

 */

public class ReaderElement extends BasicElement {

    private Connection	conn;

    private Vector	children;

    /** 

     * Construct a new ReaderElement instance

     *

     * @param conn the database connection to use to initialize 

     */

    public ReaderElement (Connection conn) {

      this.conn = conn;

      this.children = new Vector();

    }

    /** 

     * Construct a new ReaderElement instance

     *

     * @param conn the database connection to use to initialize 

     * @param nodeid the element_id for the node to be created

     */

    public ReaderElement (Connection conn, long nodeid) {

      this(conn);

      //Lookup data for self

      setElementInfo(nodeid);

      //Create child nodes (elements or attributes)

      setChildrenNodes(nodeid);

    }

    /** 

     * Construct a new ReaderElement instance

     *

     * @param conn the database connection to use to initialize 

     * @param nodeid the element_id for the node to be created

     * @param parentnodeid the id of the parent node

     * @param nodename the name of the element

     * @param nodedata the text content of the node

     */

    public ReaderElement (Connection conn, long nodeid, long parentnodeid,

                          String nodename, String nodedata) {

      this(conn);

      setElementID(nodeid);

      setParentID(parentnodeid);

      setTagName(nodename);

      appendContent(nodedata);

      // Create child nodes (elements or attributes)

      setChildrenNodes(nodeid);

    }

    /** Look up the info needed to construct this element from the DB */

    private void setElementInfo(long nodeid) {

      long element_id=0;

      long parentnodeid=0;

      String nodetype=null;

      String nodename=null;

      String nodedata=null;

      PreparedStatement pstmt;

      try {

        pstmt =

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

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

        // Bind the values to the query

        pstmt.setLong(1, nodeid);

        pstmt.execute();

        try {

          ResultSet rs = pstmt.getResultSet();

          try {

            boolean tableHasRows = rs.next();

            if (tableHasRows) {

              try {

                element_id = rs.getLong(1);

                parentnodeid = 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")) {

        setElementID(element_id);

        setParentID(parentnodeid);

        setTagName(nodename);

        appendContent(nodedata);

      }

    }

    /** Look up each child node from the DB and and create it */

    private void setChildrenNodes(long nodeid) {

      long element_id=0;

      long parentnodeid=0;

      String nodetype=null;

      String nodename=null;

      String nodedata=null;

      PreparedStatement pstmt;

      try {

        pstmt =

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

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

        // Bind the values to the query

        pstmt.setLong(1, nodeid);

        pstmt.execute();

        try {

          ResultSet rs = pstmt.getResultSet();

          try {

            boolean tableHasRows = rs.next();

            while (tableHasRows) {

              try {

                element_id = rs.getLong(1);

                parentnodeid = rs.getLong(2);

                nodetype = rs.getString(3);

                nodename = rs.getString(4);

                nodedata = rs.getString(5);

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

                  ReaderElement child = new ReaderElement(conn,

                                element_id,parentnodeid,nodename,nodedata);

                  children.add(child);

                } else if (nodetype.equals("ATTRIBUTE")) {

                  setAttribute(nodename,nodedata);

                }

              } catch (SQLException e) {

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

              }

              // Advance to the next record in the cursor

              tableHasRows = rs.next();

            }

          } 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());

      }

    }

    /** 

     * String representation for display purposes (recursively descends through

     * children to create an XML subtree)

     */

    public String toString ()

    {

        StringBuffer value = new StringBuffer();

        value.append('<');

        value.append(getTagName());

        value.append(getAttributes().toString());

        value.append('>');

        // Process children recursively here

        // Or do it in ReaderElement using a stack so we don;t have the

        // whole thing in memory at once?

        ReaderElement child = null;

        Enumeration e = children.elements();

        while (e.hasMoreElements()) {

          child = (ReaderElement)e.nextElement(); 

          value.append(child);

        }

        String cont = getContent();

        if (!cont.equals("null")) {

          value.append(cont);

        }

        value.append("</");

        value.append(getTagName());

        value.append('>');

        return value.toString();

    }

}