/*
 *  BaseLink - Generic object relational mapping
 *  Copyright (C) 2011  Ulrich Hilger, http://uhilger.de
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/
 */
package de.uhilger.baselink;

import java.sql.Blob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Types;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

/**
 * Class <code>PersistenceManager</code> stores and retrieves Java objects to and from a 
 * relational database. Any object that implements interface <code>Record</code> can be 
 * read from or written to a database using this class.
 * 
 * <p>In addition, any other class can be used directly as PersistenceManager 
 * wraps such other objects into <code>GenericRecord</code> objects implicitly.</p>
 * 
 * <p>Major aim of class <code>PersistenceManager</code> is to encapsulate the management 
 * of database related objects such as <code>Connection</code>, <code>Statement</code> and 
 * <code>ResultSet</code> to make sure proper opening and closing especially when used in 
 * conjunction with a connection pool.</p>
 * 
 * <p>In addition <code>PersistenceManager</code> provides methods that allow for an 
 * abundance of database read/write operations for convenience providing a base 
 * class to extend for individual needs.</p> 
 * 
 * @author Copyright (c) Ulrich Hilger, <a href="http://uhilger.de">http://uhilger.de</a>
 * @author Published under the terms and conditions of
 * the <a href="http://www.gnu.org/licenses/" target="_blank">GNU General Public License</a>
 * @version 3, March 22, 2011
 */
public class PersistenceManager {
  
  private static final Logger logger = Logger.getLogger(PersistenceManager.class.getName());

  public static final String NULL_STR = "null";
  /** reference to data source to use for connections in production mode */
  protected DataSource ds;
  /** reference to JDBC url to use for connections in development mode */
  protected String dburl;

  /**
   * Create a new object of class PersistenceManager
   */
  public PersistenceManager() {
    super();
  }

  /**
   * Set the JDBC driver class name
   * @param driverName  name of JDBC driver class name
   * @throws ClassNotFoundException  when driver is not found
   */
  public void setDriverName(String driverName) throws ClassNotFoundException {
    Class.forName(driverName);
  }

  /**
   * Set the database
   *
   * <p>Use either this method together with method setDriverName or
   * method setDataSourceName to indicate the connection type</p>
   *
   * @param url  JDBC url
   */
  public void setDatabase(String url) {
    this.dburl = url;
  }

  /**
   * Set the database
   *
   * <p>Use either this method or method setDataSourceName to indicate the connection type</p>
   *
   * @param driverName class name of JDBC driver
   * @param url JDBC url
   * @throws ClassNotFoundException  when driver is not found
   */
  public void setDatabase(String driverName, String url) throws ClassNotFoundException {
    Class.forName(driverName);
    this.dburl = url;
  }

  /**
   * Set name of DataSource
   *
   * <p>Use either this method or method setDatabase to indicate the connection type</p>
   *
   * @param dataSourceName  name of DataSource
   * @throws NamingException  when JNDI lookup fails
   */
  public void setDataSourceName(String dataSourceName) throws NamingException {
    Context initCtx = new InitialContext();
    Context envCtx = (Context) initCtx.lookup("java:comp/env");
    ds = (DataSource) envCtx.lookup(dataSourceName);
  }

  /**
   * Get a database connection
   * @return  a database connection
   */
  public Connection getConnection() {
    Connection c = null;
    try {
      if (dburl != null) {
        c = DriverManager.getConnection(dburl);
      } else if(ds != null) {
        c = ds.getConnection();
      } else {
        //throw new SQLException("Unable to get connection, DataSource and database URL are null.");
      }
    } catch(Exception ex) {
      ex.printStackTrace();
    }
    return c;
  }
  
  /* -------------------- deletes ---------------------------- */

  /**
   * Delete a given object from the database
   *
   * <p>Use this method for single deletes. In cases where
   * several subsequent deletes for objects of the same class
   * are required the use of method <code>delete(Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param o object to delete
   * @return  the deleted object
   */
  public Object delete(Object o) {
    return delete(o, new GenericRecord(o.getClass()));
  }

  /**
   * Delete a given object from the database
   *
   * <p>Use this method for single deletes. In cases where
   * several subsequent deletes for objects of the same class
   * are required the use of method <code>delete(Connection, Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param c  the connection to use, expected to be open and established
   * @param o  object to delete
   * @return  the deleted object
   */
  public Object delete(Connection c, Object o) {
    return delete(c, o, new GenericRecord(o.getClass()));
  }

  /**
   * Delete a given object from the database
   * @param o object to delete
   * @param record  reference to object to use to map between object and database
   * @return  the deleted object
   */
  public Object delete(Object o, Record record) {
    Connection c = null;
    try {
      c = getConnection();
      o = delete(c, o, record);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return o;
  }

  /**
   * Delete a given object from the database
   * @param c  the connection to use, expected to be open and established
   * @param o  object to delete
   * @param record reference to object to use to map between object and database
   * @return the deleted object
   */
  public Object delete(Connection c, Object o, Record record) {
    Object deletedObject = null;
    PreparedStatement ps = null;
    try {
      ps = record.getDeleteStatment(c, o);
      ps.executeUpdate();
      ps.close();
      ps = null;
      deletedObject = o;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(ps);
    }
    return deletedObject;
  }
  
  /* ---------------------- inserts -------------------- */

  /**
   * Add an object to the database
   *
   * <p>Use this method for single inserts. In cases where
   * several subsequent inserts for objects of the same class
   * are required the use of method <code>insert(Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param o  the object to add
   * @return  the added object
   */
  public Object insert(Object o) {
    return insert(o, new GenericRecord(o.getClass()));
  }

  /**
   * Add an object to the database
   *
   * <p>Use this method for single inserts. In cases where
   * several subsequent inserts for objects of the same class
   * are required the use of method <code>insert(Connection, Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param c  the connection to use, expected to be open and established
   * @param o  the object to add
   * @return  the object added to the database
   */
  public Object insert(Connection c, Object o) {
    return insert(c, o, new GenericRecord(o.getClass()));
  }

  /**
   * Add an object to the database
   * @param o object to add
   * @param record  reference to object to use to map between object and database
   * @return  the added object
   */
  public Object insert(Object o, Record record) {
    Connection c = null;
    try {
      c = getConnection();
      o = insert(c, o, record);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return o;
  }

  /**
   * Add an object to the database
   * @param c the connection to use, expected to be open and established
   * @param o object to add
   * @param record reference to object to use to map between object and database
   * @return  the object that was added
   */
  public Object insert(Connection c, Object o, Record record) {
    Object addedObject = null;
    PreparedStatement ps = null;
    try {
      ps = record.getInsertStatment(c, o);
      ps.executeUpdate();
      ps.close();
      ps = null;
      addedObject = o;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(ps);
    }
    return addedObject;
  }
  
  /* --------------------------------- updates --------------------- */

  /**
   * update an object in the database
   *
   * <p>Use this method for single updates. In cases where
   * several subsequent updates for objects of the same class
   * are required the use of method <code>update(Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param o  object to update
   * @return  the object that was updated
   */
  public Object update(Object o) {
    return update(o, new GenericRecord(o.getClass()));
  }

  /**
   * update an object in the database
   *
   * <p>Use this method for single updates. In cases where
   * several subsequent updates for objects of the same class
   * are required the use of method <code>update(Connection, Object, Record)</code>
   * is recommended instead to minimise instantiation
   * overhead.</p>
   *
   * @param c the connection to use, expected to be open and established
   * @param o object to update
   * @return  the object that was updated
   */
  public Object update(Connection c, Object o) {
    return update(c, o, new GenericRecord(o.getClass()));
  }

  /**
   * update an object in the database
   * @param o object to update
   * @param record reference to object to use to map between object and database
   * @return  the object that was updated
   */
  public Object update(Object o, Record record) {
    Connection c = null;
    try {
      c = getConnection();
      o = update(c, o, record);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return o;
  }

  /**
   * update an object in the database
   * @param c the connection to use, expected to be open and established
   * @param o object to update
   * @param record reference to object to use to map between object and database
   * @return  the object that was updated
   */
  public Object update(Connection c, Object o, Record record) {
    Object updatedObject = null;
    PreparedStatement ps = null;
    try {
      ps = record.getUpdateStatment(c, o);
      ps.executeUpdate();
      ps.close();
      ps = null;
      updatedObject = o;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(ps);
    }
    return updatedObject;
  }
  
  /* --------------- selects ---------------- */

  /**
   * Select a list of objects through a given SQL statement
   * @param sql  sql query string that designates the requested objects
   * @param record object to use to map db records to objects
   * @return a list of objects that match the given query
   */
  public List<Object> select(String sql, Record record) {
    return select(sql, record, Record.WITH_BLOBS);
  }

  /**
   * Select a list of objects through a given SQL statement
   * @param sql  sql query string that designates the requested objects
   * @param record  object to use to map db records to objects
   * @param includeBlobs  true when BLOB contents are to be retrieved, false if not
   * @return  a list of objects that match the given query
   */
  public List<Object> select(String sql, Record record, boolean includeBlobs) {
    Connection c = null;
    ArrayList<Object> list = new ArrayList<Object>();
    try {
      c = getConnection();
      list = (ArrayList<Object>) select(c, sql, record, includeBlobs);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return list;
  }

  /**
   * Select a list of objects through a given SQL statement
   * @param sql  sql query string that designates the requested objects
   * @param record  object to use to map db records to objects
   * @param includeBlobs  true when BLOB contents are to be retrieved, false if not
   * @param params  list of parameters in the order they appear in the SQL string
   * @return  a list of objects that match the given query
   */
  public List<Object> select(String sql, Record record, boolean includeBlobs, Object... params) {
    Connection c = null;
    ArrayList<Object> list = new ArrayList<Object>();
    try {
      c = getConnection();
      list = (ArrayList<Object>) select(c, sql, record, includeBlobs, params);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param c  the database connection to use for this query, expected to be established and open already
   * @param sql  sql query string that designates the requested objects
   * @param record  object to use to map db records to objects
   * @param includeBlobs  true when BLOB contents are to be retrieved, false if not
   * @return  a list of objects that match the given query
   */
  public List<Object> select(Connection c, String sql, Record record, boolean includeBlobs) {
    PreparedStatement ps = null;
    ResultSet rs = null;
    ArrayList<Object> list = new ArrayList<Object>();
    try {
      ps = c.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
      rs = ps.executeQuery();
      if (rs.first()) {
        while (!rs.isAfterLast()) {
          list.add(record.toObject(rs, includeBlobs));
          rs.next();
        }
      }
      rs.close();
      rs = null;
      ps.close();
      ps = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeResultSetFinally(rs);
      closeStatementFinally(ps);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param c  the database connection to use for this query, expected to be established and open already
   * @param sql  sql query string that designates the requested objects
   * @param record  object to use to map db records to objects
   * @param includeBlobs  true when BLOB contents are to be retrieved, false if not
   * @param params  list of parameters in the order they appear in the SQL string
   * @return  a list of objects that match the given query
   */
  public List<Object> select(Connection c, String sql, Record record, boolean includeBlobs, Object... params) {
    PreparedStatement ps = null;
    ResultSet rs = null;
    ArrayList<Object> list = new ArrayList<Object>();
    try {
      //ps = c.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
      ps = buildQuery(c, sql, params);
      rs = ps.executeQuery();
      if (rs.first()) {
        while (!rs.isAfterLast()) {
          list.add(record.toObject(rs, includeBlobs));
          rs.next();
        }
      }
      rs.close();
      rs = null;
      ps.close();
      ps = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeResultSetFinally(rs);
      closeStatementFinally(ps);
    }
    return list;
  }


  /**
   * Select a list of objects that match a given SQL statement
   * @param sql  sql query string that designates the requested objects
   * @return  a list of map objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get("fieldname")
   */
  public List<Map<String, Object>> select(String sql) {
    //Logger.getLogger(Logger.GLOBAL_LOGGER_NAME).finest(sql);
    Connection c = null;
    List<Map<String, Object>> list = null;
    try {
      c = getConnection();
      list = select(c, sql);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param sql  sql query string that designates the requested objects
   * @param includeBlobs true when content of blob coloumns should be returned, false if not
   * @return  a list of list objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get(fieldno), each element is of type String
   */
  public List<List<String>> select(String sql, boolean includeBlobs) {
    Connection c = null;
    List<List<String>> list = null;
    try {
      c = getConnection();
      list = select(c, sql, includeBlobs);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param c  the database connection to use for this query, expected to be established and open already
   * @param sql  sql query string that designates the requested objects
   * @return  a list of map objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get("fieldname")
   */
  public List<Map<String, Object>> select(Connection c, String sql) {
    PreparedStatement ps = null;
    ResultSet rs = null;
    List<Map<String, Object>> list = null;
    try {
      ps = c.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
      rs = ps.executeQuery();
      list = toList(rs);
      rs.close();
      rs = null;
      ps.close();
      ps = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeResultSetFinally(rs);
      closeStatementFinally(ps);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param c  the database connection to use for this query, expected to be established and open already
   * @param sql  sql query string that designates the requested objects
   * @param includeBlobs true when content of blob coloumns should be returned, false if not
   * @return  a list of list objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get(fieldno), each element is of type String
   */
  public List<List<String>> select(Connection c, String sql, boolean includeBlobs) {
    PreparedStatement ps = null;
    ResultSet rs = null;
    List<List<String>> list = null;
    try {
      ps = c.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
      rs = ps.executeQuery();
      list = toList(rs, includeBlobs);
      rs.close();
      rs = null;
      ps.close();
      ps = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeResultSetFinally(rs);
      closeStatementFinally(ps);
    }
    return list;
  }

  /**
   * Select a list of objects that match a given SQL statement
   * @param sql  sql query string that designates the requested objects with ? at the position of params
   * @param includeBlobs true when content of blob coloumns should be returned, false if not
   * @param params list of parameters in the order they appear in the SQL string
   * @return  a list of list objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get(fieldno), each element is of type String
   */
  public List<List<String>> select(String sql, boolean includeBlobs, Object... params) {
    Connection c = null;
    List<List<String>> list = null;
    try {
      c = getConnection();
      list = select(c, sql, includeBlobs, params);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return list;
  }
  
  /**
   * Select a list of objects that match a given SQL statement
   * @param c  the database connection to use for this query, expected to be established and open already
   * @param sql  sql query string that designates the requested objects with ? at the position of params
   * @param includeBlobs true when content of blob coloumns should be returned, false if not
   * @param params list of parameters in the order they appear in the SQL string
   * @return  a list of list objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get(fieldno), each element is of type String
   */
  public List<List<String>> select(Connection c, String sql, boolean includeBlobs, Object... params) {
    PreparedStatement ps = null;
    ResultSet rs = null;
    List<List<String>> list = null;
    try {
      ps = buildQuery(c, sql, params);
      rs = ps.executeQuery();
      list = toList(rs, includeBlobs);
      rs.close();
      rs = null;
      ps.close();
      ps = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeResultSetFinally(rs);
      closeStatementFinally(ps);
    }
    return list;
  }
  
  /* ------------------ generic SQL execution ---------- */

  /**
   * Execute an SQL statement and return keys generated in the database
   * @param sql  the statement to execute
   * @return  a list of generated keys
   */
  public List<Map<String, Object>> executeWithKeys(String sql) {
    List<Map<String, Object>> keys = null;
    Connection c = null;
    try {
      c = getConnection();
      keys = executeWithKeys(c, sql);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return keys;
  }

  /**
   * Execute an SQL statement and return keys generated in the database
   * @param c  database connection to use
   * @param sql  the statement to execute
   * @return  a list of generated keys
   */
  public List<Map<String, Object>> executeWithKeys(Connection c, String sql) {
    List<Map<String, Object>> keys = null;
    Statement s = null;
    try {
      s = c.createStatement();
      s.executeUpdate(sql, Statement.RETURN_GENERATED_KEYS);
      keys = toList(s.getGeneratedKeys());
      s.close();
      s = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(s);
    }
    return keys;
  }

  /**
   * Execute an SQL statement
   * @param sql  the statement to execute
   * @return  the number of records affected by this statement or -1 if none
   */
  public int execute(String sql) {
    int numRows = -1;
    Connection c = null;
    try {
      c = getConnection();
      numRows = execute(c, sql);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return numRows;
  }

  /**
   * Execute an SQL statement
   * @param c  database connection to use
   * @param sql  the statement to execute
   * @return  the number of records affected by this statement or -1 if none
   */
  public int execute(Connection c, String sql) {
    int numRows = -1;
    Statement s = null;
    try {
      s = c.createStatement();
      numRows = s.executeUpdate(sql);
      s.close();
      s = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(s);
    }
    return numRows;
  }

  /**
   * Execute an SQL statement
   * @param sql the SQL string with ? at the position of params
   * @param params list of parameters in the order they appear in the SQL string
   * @return  the number of records affected by this statement or -1 if none
   */
  public int execute(String sql, Object... params) {
    int numRows = -1;
    Connection c = null;
    try {
      c = getConnection();
      numRows = execute(c, sql, params);
      c.close();
      c = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeConnectionFinally(c);
    }
    return numRows;
  }

  /**
   * Execute an SQL statement
   * @param c  database connection to use
   * @param sql the SQL string with ? at the position of params
   * @param params list of parameters in the order they appear in the SQL string
   * @return  the number of records affected by this statement or -1 if none
   */
  public int execute(Connection c, String sql, Object... params) {
    int numRows = -1;
    Statement s = null;
    try {
      //s = c.createStatement();
      s = buildQuery(c, sql, params);
      if(s != null && s instanceof PreparedStatement) {
        PreparedStatement ps = (PreparedStatement) s;
        numRows = ps.executeUpdate();
        ps.close();
      }
      s = null;
    } catch (Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(s);
    }
    return numRows;
  }
  
  /**
   * Execute an SQL script
   * @param sqlScript  the SQL script to execute
   * @return an array of row counts referring to the number of affected rows of 
   * each sql statement in the script in the order of SQL commands in the script 
   * Statement.EXECUTE_FAILED indicates failure of single steps in the script 
   * Statement.SUCCESS_NO_INFO indicates successful execution without information 
   * about the number of affected rows
   */
  public int[] executeScript(String sqlScript) {
    int[] ergebnisse = null;
    Connection c = null;
    Statement s = null;
    try {
      c = getConnection();
      s = c.createStatement();
      String[] sqlKommandos = sqlScript.split(";");
      for(int i = 0; i < sqlKommandos.length; i++) {
        s.addBatch(sqlKommandos[i]);
      }
      ergebnisse = s.executeBatch();
    } catch(Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(s);
      closeConnectionFinally(c);
    }
    return ergebnisse;
  }
  
  /**
   * Execute an SQL script
   * @param c  the Connection object to use
   * @param sqlScript  the SQL script to execute
   * @return an array of row counts referring to the number of affected rows of 
   * each sql statement in the script in the order of SQL commands in the script 
   * Statement.EXECUTE_FAILED indicates failure of single steps in the script 
   * Statement.SUCCESS_NO_INFO indicates successful execution without information 
   * about the number of affected rows
   */
  public int[] executeScript(Connection c, String sqlScript) {
    int[] ergebnisse = null;
    Statement s = null;
    try {
      s = c.createStatement();
      String[] sqlKommandos = sqlScript.split(";");
      for(int i = 0; i < sqlKommandos.length; i++) {
        s.addBatch(sqlKommandos[i]);
      }
      ergebnisse = s.executeBatch();
    } catch(Exception ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      closeStatementFinally(s);
    }
    return ergebnisse;
  }
  
  /* -------- transactions ------------ */
  
  /*
      24.4.2013: BaseLink wurde um Transaktionen erweitert, 
      sodass Start und Ende von Transaktionen jeweils mit einer Zeile Code 
      moeglich ist.
      
      Connection c = getConnection();
      startTransaction(c);
      // ...hier Daten anlegen und verknuepfen...
      commit(c);
      startTransaction(c);
      // ...hier Daten anlegen und verknuepfen...
      commit(c);
      closeConnectionFinally(c);
      
  */
  
  
  public void startTransaction(Connection c) {
    try {
      c.setAutoCommit(false);
    } catch(SQLException ex) {
      logger.log(Level.SEVERE, ex.getMessage(), ex);
    } finally {
      // ..
    }
  }
  
  public void commit(Connection c) {
    try {
      c.commit();
    } catch(SQLException ex) {
      logger.log(Level.SEVERE, ex.getMessage(), ex);
    } finally {
      try {
        c.setAutoCommit(true);
      } catch (SQLException ex) {
        logger.log(Level.SEVERE, ex.getMessage(), ex);
      }
    }
  }
  
  public void rollback(Connection c) {
    try {
      c.rollback();
    } catch(SQLException ex) {
      logger.log(Level.SEVERE, ex.getLocalizedMessage(), ex);
    } finally {
      try {
        c.setAutoCommit(true);
      } catch (SQLException ex) {
        logger.log(Level.SEVERE, ex.getMessage(), ex);
      }
    }
  }
  
  /* -------- closing methods --------- */

  /**
   * Close a given result set
   * @param rs  the result set to close
   */
  public void closeResultSetFinally(ResultSet rs) {
    if (rs != null) {
      try {
        rs.close();
        rs = null;
      } catch (SQLException ex) {
        logger.log(Level.SEVERE, ex.getMessage(), ex);
      }
    }
  }

  /**
   * Close a given statement
   * @param s  the statement to close
   */
  public void closeStatementFinally(Statement s) {
    if (s != null) {
      try {
        s.close();
        s = null;
      } catch (SQLException ex) {
        logger.log(Level.SEVERE, ex.getMessage(), ex);
      }
    }
  }

  /**
   * close a given connection
   * @param c  the connection to close
   */
  public void closeConnectionFinally(Connection c) {
    if (c != null) {
      try {
        c.close();
        c = null;
      } catch (SQLException ex) {
        logger.log(Level.SEVERE, ex.getMessage(), ex);
      }
    }
  }
  
  /* ----------------------- helper methods -------------------------- */
  
  /**
   * Create an SQL statement from an SQL string and an array of parameters
   * @param sql the SQL string with ? at the position of params
   * @param params list of parameters in the order they appear in the SQL string
   * @return the SQL statement with given parameters applied
   */
  public PreparedStatement buildQuery(Connection c, String sql, Object[] params) throws Exception {
    PreparedStatement ps =
      c.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
    for(int i= 0; i < params.length; i++) {
      //buildQueryParam(ps, params[i], i);
      ps.setObject(i+1, params[i]);
    }
    return ps;
  }
    
  /**
   * Helper method that converts a ResultSet into a list of lists, one per row,
   * each row is a list of strings
   *
   * @param rs  result set to convert
   * @param includeBlobs  true when blob columns should be returned, false if not
   * @return a list of list objects, one for each record. An element in the
   * list can be accessed with list.get(recordno).get(fieldno), each element is of type String.
   * This first row has the field names
   */
  public List<List<String>> toList(ResultSet rs, boolean includeBlobs) throws SQLException {
    List<List<String>> rows = new ArrayList<List<String>>();
    ResultSetMetaData meta = rs.getMetaData();
    int columnCount = meta.getColumnCount();
    List<String> header = new ArrayList<String>();
    for (int i = 1; i <= columnCount; i++) {
      header.add(meta.getColumnName(i));
    }
    rows.add(header);
    while (rs.next()) {
      List<String> row = new ArrayList<String>();
      for (int i = 1; i <= columnCount; i++) {
        String data = null;
        if (meta.getColumnType(i) == Types.BLOB) {
          if (includeBlobs) {
            Blob blob = rs.getBlob(i);
            if(blob != null) {
              data = new String(blob.getBytes((long) 1, (int) blob.length()));
            }
          }
        } else {
          Object o = rs.getObject(i);
          if(o != null) {
            data = o.toString();
          } else {
            data = NULL_STR;
          }
          logger.finest(data.toString());
        }
        row.add(data);
      }
      rows.add(row);
    }
    return rows;
  }

  /**
   * Helper method that converts a ResultSet into a list of maps, one per row
   *
   * @param rs  database content to transform
   * @return list of maps, one per row, with column name as the key
   * @throws SQLException if the connection fails
   */
  private List<Map<String, Object>> toList(ResultSet rs) throws SQLException {
    List<String> wantedColumnNames = getColumnNames(rs);
    return toList(rs, wantedColumnNames);
  }

  /**
   * Helper method that maps a ResultSet into a list of maps, one per row
   *
   * @param rs  database content to transform
   * @param wantedColumnNames list of columns names to include in the result map
   * @return list of maps, one per column row, with column names as keys
   * @throws SQLException if the connection fails
   */
  private List<Map<String, Object>> toList(ResultSet rs, List<String> wantedColumnNames) throws SQLException {
    // TODO BLOB handling
    List<Map<String, Object>> rows = new ArrayList<Map<String, Object>>();
    int numWantedColumns = wantedColumnNames.size();
    while (rs.next()) {
      Map<String, Object> row = new TreeMap<String, Object>();
      for (int i = 0; i < numWantedColumns; ++i) {
        String columnName = wantedColumnNames.get(i);
        Object value = rs.getObject(columnName);
        if (value != null) {
          row.put(columnName, value);
          //Logger.getLogger(Logger.GLOBAL_LOGGER_NAME).finest(columnName + " " + value);
        } else {
          row.put(columnName, "");
        }
      }
      rows.add(row);
    }
    return rows;
  }

  /**
   * Return all column names as a list of strings
   *
   * @param database query result set
   * @return list of column name strings
   * @throws SQLException if the query fails
   */
  private List<String> getColumnNames(ResultSet rs) throws SQLException {
    List<String> columnNames = new ArrayList<String>();
    ResultSetMetaData meta = rs.getMetaData();
    int numColumns = meta.getColumnCount();
    for (int i = 1; i <= numColumns; ++i) {
      String cName = meta.getColumnName(i);
      columnNames.add(cName);
    }
    return columnNames;
  }
}