Source code: jflight/db/AbstractDAO.java

   /**
    * AbstractDAO.java
    *
    * @author Created by Ingo Koerber
    */
   
   package jflight.db;
   
   import java.util.*;
  import java.sql.*;
  import jflight.tools.*;
  
  /**
   *  the base class for all Data access objects
   */
  public abstract class AbstractDAO
  {
    protected abstract String getPkColumnName();
    protected abstract String getTableName();
    protected abstract Vector load(PreparedStatement ps) throws SQLException;
    
    public Vector fields = new Vector();
  
    protected Vector getFieldMap(){return fields;};
  
    protected String getCreateTableStmt()
    {
      StringBuffer buf = new StringBuffer("create table");
      buf.append(" ").append(getTableName()).append(" (");
      Vector fields = getFieldMap();
  //    Iterator iterator = fields.iterator();
  //    while(iterator.hasNext()) {
  //      String[] mapping = (String[])iterator.next();
      for( int cnt=0;; cnt++ )
      {
              try {
                  String[] mapping = (String[])fields.elementAt(cnt);
            buf.append(mapping[0]).append("=?").append(", ");
              } catch (Exception e) {
                  break;
              }
      }
      buf.append(getPkColumnName()).append(" integer)");
      return buf.toString();
    }
    
    protected String getUpdateStmt()
    {
      JfStringBuffer buf = new JfStringBuffer("update");
      buf.append(" ").append(getTableName()).append(" set ");
      Vector fields = getFieldMap();
  //    Iterator iterator = fields.iterator();
  //    while(iterator.hasNext()) {
  //      String[] mapping = (String[])iterator.next();
      for( int cnt=0;; cnt++ )
      {
              try {
                  String[] mapping = (String[])fields.elementAt(cnt);
            buf.append(mapping[0]).append("=?").append(", ");
              } catch (Exception e) {
                  break;
              }
      }
      buf.deleteCharAt(buf.lastIndexOf(", "));
          // workaround for jdk 1.1:
          // remove the ",": Ingo: ist that ok???
  /*
          String str1, str2;
          str1 = new String(buf);
          int index;
          index = str1.lastIndexOf(", ");
          if( index != -1 ) {
              str2 = new String(str1.substring(0,index-1));
              str2.concat(str1.substring(index+1, str1.length()-1));
              buf = new StringBuffer(str2);
          }
  */
          buf.append("where ").append(getPkColumnName()).append("=?");
      return buf.toString();
    }
    
    /**
     * Method getInsertStmt
     *
     * @return   the insert statement which is necessary to insert an object
     * in the database
     *
     */
    protected String getInsertStmt()
    {
      StringBuffer buf = new StringBuffer("insert into ");
      buf.append(getTableName()).append(" values(");
      Vector fields = getFieldMap();
      for(int i=0;i<fields.size();i++)
        buf.append("?, ");
      
      buf.append("?)");
      return buf.toString();
    }
 
   /**
    * Method createTable create the necessary table for this object type
    *
    */
   protected void createTable()
   {
     try
     {
       Connection conn = ConnectionManager.getInstance().getConnection();
       Statement statement = conn.createStatement();
       statement.execute(this.getCreateTableStmt());
     }
     catch (SQLException e) {}
   }
 
   /**
    * Method getNextID gets the next valid primary key
    *
    * @param    conn                a  Connection to database
    *
    * @return   the next valid primary key, for this object type
    *
    * @throws   SQLException
    *
    */
   protected int getNextID(Connection conn)
     throws SQLException
   {
     int ret = 0;
     Statement statement = conn.createStatement();
     ResultSet rSet = statement.executeQuery("select max(" + this.getPkColumnName() + ") from " + this.getTableName());
     if(rSet.next()) ret = rSet.getInt(1);
     rSet.close();
     statement.close();
     return ret+1;
   }
   
   /**
    * Method loadAll loads all object from database
    *
    * @return   a Vector of objects
    *
    */
   public Vector loadAll()
   {
     Vector all = new Vector();
     Connection conn = null;
     
     try
     {
       conn = ConnectionManager.getInstance().getConnection();
       PreparedStatement statement = conn.prepareStatement("select * from " + this.getTableName());
       all = load(statement);
       statement.close();
       conn.commit();
     }
     catch (SQLException e)
     {
       e.printStackTrace();
     }
     finally
     {
       try
       {
         conn.rollback();
         conn.close();
       }
       catch (SQLException e) {e.printStackTrace();}
     }
     return all;
   }
 
   /**
    * Method findDOAByKey find the object with specified primary key in database
    *
    * @param    pk                  a primary key
    *
    * @return   an Object with the specified pk
    *
    */
   public Object findDOAByKey(int pk)
   {
     Vector daos = new Vector();
     Connection conn = null;
     try
     {
       conn = ConnectionManager.getInstance().getConnection();
       PreparedStatement statement =
         conn.prepareStatement("select * from " + this.getTableName() +
                     " where " + this.getPkColumnName() + " = ?");
       statement.setInt(1,pk);
       daos = load(statement);
       statement.close();
       conn.commit();
     }
     catch (SQLException e)
     {
       e.printStackTrace();
     }
     finally
     {
       try
       {
         conn.rollback();
         conn.close();
       }
       catch (SQLException e) {}
     }
     if(daos.isEmpty()) return null;
     return (Object)daos.elementAt(0);
   }
 
   /**
    * Method findObjects in database
    *
    * @param    whereClause         clause in sql statement after: select * from table where
    * @param    queryParameters     an Object[] with retrieved objects
    *
    * @return   an Object
    *
    */
   public Object findObjects(String whereClause, Object[] queryParameters)
   {
     Vector objects = new Vector();
     Connection conn = null;
     try
     {
       conn = ConnectionManager.getInstance().getConnection();
       String sql = "select * from " + this.getTableName() + " where " + whereClause;
       PreparedStatement statement =
         conn.prepareStatement(sql);
       for(int i=0;i<queryParameters.length;i++)
         statement.setObject(i+1,queryParameters[i]);
       objects = load(statement);
       statement.close();
       conn.commit();
     }
     catch (SQLException e)
     {
       e.printStackTrace();
     }
     finally
     {
       try
       {
         conn.rollback();
         conn.close();
       }
       catch (SQLException e) {}
     }
     if(objects.isEmpty()) return null;
     return objects.elementAt(0);
   }
 
 }