cardfile.java

有关JDBC的使用一些编程实例,有关与数据库连接的代码

  /**
   *
   * update()
   *
   * Send an update to the mSQL server.
   *
   */
  protected void update() {

    // construct an update string for each of the columns
    // except for the id. This is used as the criteria
    // for the update, so we probably don't want to
    // update it...

    String sql = "update cardfile " +
                 " set name    = '" + txt_name.getText() + "', " +
                 "     address = '" + txt_address.getText() + "', " +
                 "     city    = '" + txt_city.getText() + "', " +
                 "     state   = '" + txt_state.getText() + "', " +
                 "     zip     = '" + txt_zip.getText() + "', " +
                 "     country = '" + txt_country.getText() + "', " +
                 "     phone   = '" + txt_phone.getText() + "' " +
                 " where id = " + txt_id.getText();
    try {

      // send the query

      MsqlResult    result = msql.Query(sql);

      // call getRow() to refresh the form. This really shouldn't
      // be necessary, but it lets us know what the update did.

      getRow();
    } 
    catch(MsqlException e ) {
      e.printStackTrace();      
    }
 
  }

  /**
   * handleEvent
   *
   * Deal with things the user did...
   */
  public boolean handleEvent(Event event) {

    switch(event.id) {

    // deal with action buttons

    case Event.ACTION_EVENT:

      // if the next button was pushed, then I want to
      // increment currentRow. But, if that would push
      // it out past cardfileKeys.size(), I will just
      // wrap around to the beginning (zero).

      if (event.target == next) {
	if (currentRow + 1 == cardfileKeys.size()) {
	  currentRow = 0;
	} else {
	  currentRow++;
	}

	// call getRow() to update the form
	getRow();
	  
      }

      // if the user pushed the previous button, then
      // I want to decrement currentRow. If currentRow 
      // already zero, then decrementing further would
      // probably throw some evil exception, so I'll
      // set it to cardfileKeys.size() - 1, which is the
      // index of the last element.

      if (event.target == previous) {
	if (currentRow  == 0) {
	  currentRow = cardfileKeys.size() - 1;
	} else {
	  currentRow--;
	}

	// call getRow() to update the form
	getRow();
	
      }

      // if the user pressed delete, then call the
      // delRow() method.

      if (event.target == delete) {
	delRow();
      }
      
      // if the user pressed quit, then let's get out of here!

      if (event.target == quit) {
	System.exit(0);
      }

      // if the user wants to edit the current row,
      // then set the formstate as appropriate, and 
      // call the setEdit() method.

      if (event.target == edit) {
	formstate = "edit";
	setEdit();
      }

      // in case the user presses the new button, I
      // want to 1) clear the form, 2) set the formstate
      // to "new", 3) let them modify the id field, and
      // 4) call setEdit()

      if (event.target == newrow) {
	clearForm();
	formstate = "new";
	txt_id.setEditable(true);	

	setEdit();
      }

      // in case the user hits the save button, I need
      // to distinguish between "new" and "edit" mode,
      // so I know whether to call save() or update().
      // Also, I need 
      if (event.target == save) {
	if (formstate.equals("new")) {
	  save();
	  txt_id.setEditable(false); // make the id field uneditable
	}
	if (formstate.equals("edit")) {
	  update();
	}

	// set the formstate to "browse", and call setBrowse()
	formstate = "browse";
	setBrowse();
      }

      // if the user pressed cancel, return the formstate to browse

      if (event.target == cancel) {
	
	// if it was new, make sure that they can't edit the
	// id field...

	if (formstate.equals("new")) {
	  txt_id.setEditable(false);
	} 

	// return the formstate to browse, call getRow()
	// to retrieve the row they were looking at
	// before editing or adding, and call setBrowse()

	formstate = "browse";
	getRow();
	setBrowse();
      }

      break;

    // in case they closed the window, then take
    // it as a sign that they want to quit
    case Event.WINDOW_DESTROY:
	System.exit(0);
        break;            // hmmm...

    // just pass these on
    case Event.MOUSE_DOWN:
    case Event.MOUSE_UP:
    case Event.MOUSE_DRAG:
    case Event.KEY_PRESS:
    case Event.KEY_ACTION:
    case Event.KEY_RELEASE:
    case Event.KEY_ACTION_RELEASE:
    case Event.GOT_FOCUS:
    case Event.LOST_FOCUS:
    case Event.MOUSE_ENTER:
    case Event.MOUSE_EXIT:
    case Event.MOUSE_MOVE:
      return false;
    }

    return true;
  }

  /**
   * setEdit()
   *
   * prepare the form for editing/adding
   *
   */
  protected void setEdit () {
    
    // disable all these buttons

    next.setEnabled(false);
    previous.setEnabled(false);
    newrow.setEnabled(false);
    edit.setEnabled(false);
    delete.setEnabled(false);

    // set everything except the id to be editable
    txt_name.setEditable(true);
    txt_address.setEditable(true);
    txt_city.setEditable(true);
    txt_state.setEditable(true);
    txt_zip.setEditable(true);
    txt_country.setEditable(true);
    txt_phone.setEditable(true);

    // enable these two buttons

    save.setEnabled(true);
    cancel.setEnabled(true);
  }

  /**
   * setBrowse()
   *
   * prepare the form for viewing
   *
   */
  protected void setBrowse() {

    // enable all these buttons
    
    next.setEnabled(true);
    previous.setEnabled(true);
    newrow.setEnabled(true);
    edit.setEnabled(true);
    delete.setEnabled(true);

    // disable the fields
    
    txt_name.setEditable(false);
    txt_address.setEditable(false);
    txt_city.setEditable(false);
    txt_state.setEditable(false);
    txt_zip.setEditable(false);
    txt_country.setEditable(false);
    txt_phone.setEditable(false);
    txt_id.setEditable(false);
   
    // disable these buttons

    save.setEnabled(false);
    cancel.setEnabled(false);
  }

  /**
   * getRow()
   *
   * retrieve a row from the table, using the one indicated by
   * cardfileKeys.elementAt(currentRow)
   *
   */
  protected void getRow() {

    // if there are no rows to process, just clear
    // the form and return...

    if (cardfileKeys.isEmpty()) {
      clearForm();
      return;
    }

    try {

      // issue a select statement to get the row which is
      // pointed to by currentRow. Unless we have an
      // integrity violation, this should only be one 
      // row.

      MsqlResult    result = msql.Query("select * from cardfile where id = " +
					cardfileKeys.elementAt(currentRow));
      
      // ahhh... catalog data. Since each textfield is
      // represented in the columnmap hash, keyed by
      // the column name to which it corresponds, I
      // can use the array of column names to map each
      // column in the result set to the fields on the
      // form.

      MsqlFieldDesc field[]  = result.ListFields();

      // get the number of columns

      int cols = result.NumFields();

      // retrieve the row

      String row[];
      row = result.FetchRow();

      // loop over each column, up until the number indicated
      // by the call the NumFields()

      for(int i=0; i < cols; i++) {

	// get the name of the column from field[i].FieldName()
	
	String col_name = field[i].FieldName();

	// this gets the object from columnmap (a TextField) which
	// is keyed by the name of the column in col_name
	// here, we simply call the setText() method of that TextField
	// object to the value of the column.

	((TextField) columnmap.get(col_name)).setText(row[i]);
	  
      }

    } 
    catch (MsqlException e) {
      e.printStackTrace();
    }
    catch (ArrayIndexOutOfBoundsException e) {
      // ahhh, just ignore it!
    }
  }

  /**
   * delRow()
   *
   * deletes the current row.
   *
   */
  protected void delRow() {

    try {

      // issue the query to delete the row
      
      MsqlResult    result = msql.Query("delete from cardfile where id = " +
					cardfileKeys.elementAt(currentRow));

      // Oh yeah, don't forget to remove the element from
      // cardfileKeys.

      cardfileKeys.removeElement(cardfileKeys.elementAt(currentRow));

      // let's just be lazy and return to row 0...

      currentRow = 0;

      // call getRow() to refresh the form with the current record.

      getRow();

    } 
    catch (MsqlException e) {
      e.printStackTrace();
    }
  }

  // our little friend main, who makes it all happen
  
  public static void main(String[] args) {

    // make a new CardFile, pack() it and show() it.
    CardFile cardfile = new CardFile();
    cardfile.pack();
    cardfile.show();

  }

}